Comparative analysis of sentinel lymph node localization techniques: evaluating Magtrace (superparamagnetic iron oxide nanoparticle) against conventional technetium-99m (Tc-99m) and blue dye methods for breast cancer, and assessment of patient satisfaction

Introduction

Sentinel lymph node biopsy (SLNB) plays a crucial role in diagnosing and treating early breast cancer. It is considered the standard of care for patients with early breast cancer and clinically and radiologically negative axillary lymph nodes, replacing axillary lymph node dissection (ALND) as a staging procedure (1,2). This shift has contributed to an improved quality of life for women undergoing breast cancer treatment (3-5). The current widely adopted technique for sentinel lymph node (SLN) identification is the dual-modality method, which involves injecting technetium-99m (Tc-99m) labeled nanocolloid and blue dye (BD) into the peritumoral or periareolar region (1,6).

In a large meta-analysis of 8,000 patients with early-stage breast cancer who underwent SLN mapping using radiocolloid, BD, or both, conducted by Kim et al., the SLN identification rate was reported to be 96% (7). The identification rate varied between 41% and 100%. Another meta-analysis involving more than 9,000 patients found that the dual-modality technique performed better than both dye-only and radiocolloid-only techniques. The dual-modality approach resulted in a lower false-negative rate of 5.9%, while the dye-only and radiocolloid-only techniques had false-negative rates of 8.6% and 7.4%, respectively (8).

Despite its effectiveness, the dual-modality technique has certain drawbacks, including radiation exposure for both patients and healthcare personnel, stringent legislative controls, limitations in the availability of Tc-99m, and the risk of allergic reactions to BD (9). Additionally, the use of Tc-99m, with its short half-life and dependence on the Department of Nuclear Medicine, poses logistical challenges, particularly in relation to operating room scheduling (3). These limitations highlight the clinical need for alternative, radiation-free methods that are both accurate and overcome these drawbacks.

One of the novel techniques studied in recent years is Magtrace, a superparamagnetic iron oxide (SPIO) nanoparticle used for identifying the SLN in early breast cancer. It has been shown to be equivalent to the conventional radioisotope in terms of detection rates, false-negative rates, and safety (1,9-13). The Magtrace and Sentimag system by Endomag consists of a magnetic liquid tracer (Magtrace) and a handheld magnetic sensing probe (Sentimag, Cambridge, UK). Magtrace can be injected into the breast days before surgery or 20 minutes prior to the operation while the patient is asleep. The dual-tracer system visualizes as a dark brown or black lymph node and is audibly detected with the Sentimag probe.

An important feature of Magtrace is its ability to persist in the SLNs for 30 days, providing a longer-lasting effect compared to Tc-99m and BD, which may migrate to secondary lymph nodes or fade away over time. This extended duration offers breast surgeons increased flexibility in planning of patient care (14). Additionally, a study by Karakatsanis and colleagues suggested that Magtrace can be injected during mastectomy for ductal carcinoma in situ (DCIS). If invasive cancer is later discovered, SLNB can be performed, reducing the overall number of SLNB procedures. This approach helps mitigate the 1 to 8 percent risk of lymphedema associated with SLNB for most patients and simultaneously reduces costs (4,13,15-17).

The most frequently reported side effect of Magtrace injection into the breast is grey-brown discoloration resembling bruising. This discoloration was observed in 15% of patients by Lorek and colleagues (17). Follow-up visits revealed that the discoloration gradually faded to about 50% of its initial diameter and intensity within 9 months, disappearing completely after 18 months in most cases. Another study by Rubio et al. found that 19% of patients experienced skin discoloration, which resolved after 6 months (18).

In our institution, Monday theatre schedules are often delayed due to the unavailability of the Tc-99m isotope necessary for localizing SLNB before 10 am. This delay leads to inefficiencies and resource wastage, with an average of two Monday theatre lists affected. Additionally, recent local shortages of the isotope have worsened the problem. To address this, we’ve trialed Magtrace as an alternative to the radiocolloid localization of SLN. The study aims to compare the experience of using Magtrace versus the current dual technique of Tc-99m and BD, with a focus on improving surgical efficiency. Additionally, we assess patient satisfaction, comparing Magtrace vs. Tc-99m isotope injection in terms of discomfort, staining, and resolution of both. We present this article in accordance with the STROBE reporting checklist (available at https://abs.amegroups.com/article/view/10.21037/abs-24-23/rc).

Methods

This retrospective study conducted at Neath Port Talbot Hospital in Wales included all patients in one surgeon’s practice, diagnosed with node-negative invasive breast cancer (IBC) (cT1 to T3, cN0, cM0) between February 2023 and January 2024. The exclusion criteria for the study ruled out patients with known hypersensitivity to iron oxide or dextran compounds, hemochromatosis, metal implants in the axilla or chest, and functioning pacemakers, as these are recognized contraindications to the use of Magtrace (14).

In this retrospective study conducted at a single institution, data from 50 patients were analyzed. The patients were evenly divided into two groups: the study arm, which utilized Magtrace for SLN localization, and the control arm, which employed the conventional method involving Tc-99m and BD. Allocation to these groups was based on the order of patient presentation starting from February 2023. The initial 25 patients meeting the specified criteria underwent SLNB using the conventional dual technique and were assigned to the Tc-99m/BD group, while the subsequent 25 patients underwent SLNB using Magtrace and were assigned to the Magtrace group. All SLN biopsies were performed by one surgeon.

In the study arm, Magtrace injection was administered, on average, 5 days prior to surgery, with a range of 0 to 20 days. The injection was given peri-areolarly in the ipsilateral breast at a depth of 1.5 to 2 cm, and at least 3 cm away from the tumor if Magseed was also used. Two out of 25 patients received a 2ml injection of Magtrace, as the injection was administered on the morning of surgery requiring greater volume, while the remaining patients in the Magtrace group were administered a 1 mL injection on average 5 days prior to surgery. In the control arm Tc-99m and BD injections were both delivered subcutaneously in periareolar area in the quadrant of the tumor location. Administration of Tc-99m was performed in the Department of Nuclear Medicine. Demographic data, including age and body mass index (BMI), along with menopausal status, neoadjuvant chemotherapy (NACT) status, type of operation performed, tumor histology and its size, receptor and nodal status, average number of SLN’s retrieved, subsequent axillary node clearance, and follow-up time, were gathered. In cases of NACT, pre-treatment tumor size was considered. These characteristics were then compared between the Magtrace group and the Tc-99m/BD group. The study additionally recorded patient experiences including discomfort during Magtrace and Tc-99m injections, duration of discomfort, skin discoloration, and staining duration post-Magtrace vs. BD injection. Overall patient satisfaction was also noted. This was achieved through a questionnaire completed by patients post-operatively (Figure 1). The minimum follow-up period utilizing the questionnaire was 2 months, ranging from 3–13 months. The study utilized the 11-point Numerical Pain Rating Scale (NPRS) to assess discomfort during injections. Participants were asked to select a whole number from 0 to 10 to indicate the intensity of their discomfort, with 0 indicating no pain, 1–3 indicating mild pain, 4–6 indicating moderate pain, and 7–10 indicating severe pain. The aim was to compare the discomfort experienced between the two study arms based on these parameters.

Figure 1 Patient satisfaction questionnaire.

Statistical analysis

The study utilized SPSS 25.0 software (IBM Corp., Armonk, NY, USA) for statistical analysis, describing continuous variables using mean ± standard deviation and range. Missing data was handled by reporting valid percentages only.

Ethical consideration

The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study was approved by the ethics committee of Cwm Taf Morgannwg University Health Board and individual consent for this retrospective analysis was waived.

Results

In the study conducted between February 2023 and January 2024, 50 patients underwent mastectomy or breast conserving surgery along with SLNB. The average follow-up period was 7.3 months (ranging, 2 to 13 months), with 4.8 months (ranging from 2 to 8 months) in the Magtrace group and 9.9 months (ranging from 7 to 13 months) in the Tc-99m/BD group. SLNs were identified using Magtrace in 25 patients (50%) and using the Tc-99m/BD dual technique in the other 25 patients (50%). Out of the total 50 SLNB procedures performed, 70% were in the setting of breast conserving surgery, while 30% were accompanying mastectomy.

The study involved patients aged between 28 and 81 years, with a median age of 57 (±13.3) years. In the Magtrace group, the median age was 56 (±11.9) years, while in the Tc-99m/BD group, it was 60 years (±14.7). The average BMI was 29 (±6.1) kg/m², with no significant difference between the two study arms (P=0.65). There were only 7 (3.5%) patients who underwent NACT prior to surgery, with an equal distribution between the Magtrace and Tc-99m/BD groups. Regarding menopausal status, 34% of women were pre-menopausal, 2% were peri-menopausal, and 64% post-menopausal, with no notable difference between the two study arms (P=0.55) (Tables 1,2).

Overall, the mean tumor size was 31.2 mm, with a range of 6 to 118 mm. In the Magtrace group, the mean tumor size was 37.6 mm, whereas in the Tc-99m/BD group, it was 28.2 mm. However, there was no statistically significant difference between the two groups (P=0.13). Among all tumors, 39 (79.6%) were estrogen receptor (ER)+ and human epidermal growth factor receptor 2 (Her2)−, 5 (10.2%) were ER+ and Her2+, and 1 (2%) were ER− and Her2+. Triple negative breast cancer accounted for 8.2% of all tumors. There was no significant statistical difference in receptor status between Magtrace and Tc99m/BD groups (P=0.26) (Tables 2,3).

The study analyzed the prevalence of histopathologic types of breast cancers, finding that invasive ductal carcinoma (IDC) was the most common type, accounting for 30%, followed by invasive lobular carcinoma (ILC) at 20%, and IDC combined with DCIS at 26%. In the Magtrace group, IDC comprised 32% of tumors, ILC represented 28%, and IDC combined with DCIS was found in 20%. Similarly, in the Tc-99m/BD group, IDC accounted for 28% of tumors, ILC for 12%, and IDC combined with DCIS for 32%, with no significant difference between the groups (P=0.76) (Table 4).

The analysis of tumor and nodal stages, as well as tumor grades, revealed that in the Magtrace group, Tis, pT1, pT2, and pT3 stages constituted 4%, 32%, 36%, and 28% respectively. Similarly, in the Tc-99m/BD group, 4% of tumors were Tis, 44% were pT1, 48% were pT2, and 4% were pT3, showing no significant difference between the two groups (P=0.14).

Regarding nodal status, pN0 was observed in 76% of Magtrace cases compared to 91.7% of Tc-99m/BD cases. pN1 was noted in 12% of Magtrace cases and 8.3% of Tc-99m/BD cases. pN2 nodal status was recorded in 12% of Magtrace cases, while no pN2 graded lymph nodes were found in the Tc-99m/BD group, indicating a significant distinction in nodal status between the two groups (P<0.001).

When comparing tumor grades between the Magtrace and Tc-99m/BD study arms, Grade 1 tumors were found in 4% of both Magtrace and Tc-99m/BD cases. Grade 2 tumors were the most prevalent in both groups, constituting 76% of Magtrace and 56% of Tc-99m/BD cases. Grade 3 tumors represented 16% of Magtrace cases and 28% of Tc-99m/BD cases. However, there was no statistically significant difference in tumor grade between the two study arms (P=0.46) (Table 3).

The average number of SLNs retrieved during SLNB was 2.5 (±1.7). In the Magtrace group, the mean number of SLNs retrieved was 3.2, compared to 1.9 in the Tc-99m/BD group, showing a significant difference (P=0.03) (Table 2). Following SLNB, macrometastases were found in SLNs of 6 (30%) of patients in the Magtrace group and 3 (15%) in the Tc-99m/BD group. In the Magtrace group, 5 out of 6 patients requiring completion axillary node clearance (ANC) underwent the procedure, with 1 opting for radiotherapy to axillary lymph nodes. In the Tc-99m/BD group, 2 out of 3 patients completed ANC, while 1 chose radiotherapy due to co-morbidities (Table 5). In the Magtrace group, 3 out of 6 patients had 4 or more SLNs positive for macrometastasis, while the other 3 patients had 1 positive SLN. Four patients underwent mastectomy, and two underwent breast-conserving surgery. In the Tc-99/BD group, all three patients had 1-2 SLNs positive for macrometastasis, and two of these patients underwent mastectomy. The average number of SLNs retrieved in Magtrace patients requiring ANC was 3.2, compared to 1.3 in the Tc-99m/BD group. This difference was statistically significant (P=0.03).

This study compared patient satisfaction regarding injection experiences between Magtrace, a magnetic liquid tracer, and Tc-99m labeled nanocolloid, with 20 patients in each group. The analysis focused on injection discomfort and skin discoloration. Results indicated that during injection, 5% of patients in the Magtrace group and 65% in the Tc-99m group reported no pain during the injection. Mild pain (scale 1–3) was reported by 55% of Magtrace-injected patients compared to only 5% in the Tc-99m group. Moderate (scale 4–6) and severe pain (scale 7–10) were reported in 25% and 15% of the Magtrace group respectively, and 20% and 10% in the Tc-99m group, respectively. Overall, there was a significant difference between the two groups (P<0.001).

The resolution of injection discomfort in patients who experienced it was also assessed. In the Magtrace injection group, 18 patients (94%) reported immediate and complete resolution of discomfort, compared to 6 patients (85.7%) in the Tc-99m group. Only one patient in the Magtrace group reported discomfort lasting for a few hours, while one patient in the Tc-99m group reported discomfort lasting about 30 minutes. There was no significant difference between the two groups (P=0.21).

Skin staining was present in 30% of cases after Magtrace injection, while it was present in 80% of patients after BD injection (P=0.001). Among patients experiencing staining, 10% of Magtrace staining resolved at 3 months, another 10% at 6 months, while 10% persisted over 6 months. For patients receiving BD injection, 25% reported resolution of staining at 3 months, 20% at 6 months, and 35% had staining present after 6 months. This difference was statistically significant (P=0.03).

In terms of overall patient satisfaction, 100% (19/19) of patients experiencing Magtrace injection 1 week before surgery were satisfied with the process. One patient in this group did not respond to this question. 85% of patients in Tc-99m group were satisfied with injection on the day of surgery. However, 15% of patients found the process stressful.

From February to August of 2023, when employing the dual technique of Tc-99m and BD for localizing SLNB, 25% of theater lists experienced delays of 1.5–2 hours due to late delivery of Tc-99m. However, no delays associated with the SLNB procedure were recorded during the period from August 2023 to January 2024 when using Magtrace.

Discussion

In our institution, delayed delivery of Tc-99m injection frequently causes inefficiency in the theater, leading to resource wastage. On average, this results in about 25% of theater sessions being delayed by 1.5–2 hours each. Considering the cost of £17 per minute of delay, based on King’s Funds data, this translates to a financial loss ranging from £1,530 to £2,040 for every delayed session. Furthermore, the delay leads to a reduction in theatre efficiency, decreasing the number of patients that can be operated on from 5 to 3–4 per full theatre session. In Magtrace and Sentimag system used for locating SLNs in breast cancer, The National Institute for Health and Care Excellence (NICE) guidelines of 2022, resource use data from three National Health Service (NHS) trusts lacking on-site access to radiopharmacy or nuclear medicine were examined. The data revealed that delays in surgery or staff shortages caused a loss of 30 minutes of theatre time in 20% of all SLN biopsies (14) which is in line with our findings. During our study, when utilizing Magtrace for localizing SLNB, no delays related to the SLNB procedure in starting the theater list were recorded. This suggests an improvement in the efficiency of running the theater list.

To address these inefficiencies experienced in our theatres, we conducted this trial to explore Magtrace as a potential alternative to the current dual technique of Tc-99m/BD for SLN localization. The study compared two groups: one using Magtrace and the other using Tc-99m/BD. Demographics, clinical characteristics, and histopathologic features of both groups were analyzed and presented in Tables 1-4. Furthermore, patient-reported experiences were documented and compared between the two groups in Table 6.

Overall, the demographics, clinical, and histopathologic characteristics were evenly matched between the two study arms, except for tumor and nodal stage. While there were different proportions of Tis, pT1, pT2, and pT3 stages in each group, the overall distribution did not show a significant difference between the Magtrace and Tc-99m/BD groups.

The nodal status (pN), however, showed significant differences between the two groups. The Tc-99m/BD group had a higher prevalence of pN0 status compared to the Magtrace group. Conversely, pN2 nodal status was only observed in the Magtrace group, with none found in the Tc-99m/BD group.

In terms of the success of retrieving SLN, there was a higher number of retrieved lymph nodes in the Magtrace group, compared to the Tc-99m/BD group, potentially leading to a decreased false negative rate. This was a statistically significant finding which was also noted by Shams and colleagues who looked at care process optimization, reimbursement, surgical time, and patient comfort of Magtrace compared with standard Tc-99m. The same was observed by Man et al. who demonstrated a higher mean number of SLNs harvested in SPIO group when compared to the Tc-99m group (3.3 versus 2.8, P=0.039) (3,19). In 2021 Makita and colleagues reported the average number of nodes removed by the SPIO method was significantly greater than that removed by the Tc-99m/BD method (2.6 vs. 1.9, P<0.001) (20). In contrast, Douek et al. compared 170 SLNB procedures and reported no difference in the number of SLN retrieved using magnetic vs. standard tracers (radioisotope with or without BD) (21). In their series, the lymph node retrieval rate was 2.5 nodes per patient overall, 1.9 nodes per patient with the standard technique, and 2.0 nodes per patient with the magnetic technique.

The higher mean number of SLNs harvested in the SPIO group compared to the Tc-99m group remains unclear. Makita and colleagues found that the number of SPIO nodes harvested was significantly influenced by the injected dose, with higher doses needed for patients with obesity and old age due to slower lymphatic flow (20). Pantiora et al.’s meta-analysis of 20 comparative studies indicated that factors such as neoadjuvant therapy, injection site, injection volume, or nodal metastasis burden did not affect detection rates (22). However, injecting SPIO over 24 hours before surgery improved detection rates. SPIO use resulted in slightly more SLNs retrieved (pooled mean 1.96 vs. 1.89) and a higher nodal detection rate (94.1% vs. 83.5%; RR 1.098, 1.058 to 1.140; P<0.001; low-certainty evidence). Meta-regression showed that injecting SPIO over 24 hours before surgery increased the nodal yield compared to Tc-99m/BD (22).

In our study, patients’ age and BMI were similar across groups, with an average Magtrace dose of 1ml injected five days before surgery, except for three patients who received 2ml on the surgery day. The average number of SLNs retrieved in these 3 patients was 4. All SLNs were identified as either hot or stained, or both. The retrieval process concluded when no significant isotope or Magtrace readings were detected following the 10% rule, and no further stained lymph nodes were visible. According to Endomag, if a SLN shows a maximum reading of 9,999 on the Sentimag system, the actual reading might be higher. This can affect the application of the 10% rule, which dictates that any node with a radiation count exceeding 10% of the hottest node should be removed. If the true reading of the hottest node is higher than 9,999, the 10% threshold might be higher than 1,000. Consequently, surgeons might remove more lymph nodes, including those reading 1,000, even if they don’t meet the 10% rule. This situation may lead to a higher SLN retrieval rate in the Magtrace group.

In our study out of 25 patients in the Magtrace group, 15 had positive SLN, whereas only 4 patients out of 25 in the Tc-99m/BD group had positive SLN. This difference in the number of positive SLNs may be attributed to the higher average retrieval of lymph nodes in the Magtrace group and possibly lower false negative rate. The higher number of lymph nodes retrieved in the Magtrace group may also account for the observed difference in nodal status between the two groups. We also found that in the Magtrace study arm, 30% of patients required completion ANC, compared to 15% in the Tc-99m/BD group. In the Magtrace group, 3 out of 6 patients had 4 or more SLNs with macrometastasis, whereas all 3 patients needing ANC in the Tc-99m/BD group had 1–2 positive SLNs. The reason for more patients needing ANC and having more affected lymph nodes in the Magtrace group is unclear. Nonetheless, it’s crucial to emphasize that the study’s sample size is insufficient for drawing definitive conclusions. Larger studies are necessary to establish any potential connections reliably.

The approach to axillary management in breast cancer has significantly evolved over the past decade. Traditionally, any level of axillary nodal involvement necessitated ALND. However, findings from the American College of Surgeons Oncology Group Z0011 trial have challenged this practice. The trial demonstrated that selected patients with T1–2 breast tumors and limited nodal disease who underwent breast-conserving therapy could avoid ALND without negatively impacting locoregional recurrence or disease-free survival (23,24). Nevertheless, the trial’s exclusion of certain patient groups, such as those undergoing mastectomy, those with more than 2 positive SLN’s, or those with imaging-detected lymph node metastases, has led to ambiguity in guidelines and complicated management decisions for patients falling outside the trial’s criteria.

Following the publication of the ACOSOG Z0011 trial, national trends have shown a significant decrease in the performance of ALND (24). However, many centers still consider ALND standard care for clinically node-positive breast cancer patients (25,26). Axillary radiotherapy has been shown to provide comparable axillary control for patients with T1–2 primary breast cancer and no palpable lymphadenopathy, with significantly less morbidity compared to ALND (27). In our study, one patient in each study arm received axillary radiotherapy due to multiple co-morbidities.

Presently, all our patients with at least one SLN positive for macrometastasis undergo ALND, except when limited by co-morbidities, irrespective of whether they had a mastectomy or breast-conserving surgery.

A pathologic complete response (pCR) of the axilla (ypN0) occurs in about one-third of patients who are clinically node-positive (cN+) following NACT. The pCR rates exceed 50% in patients with triple-negative and HER2-positive breast cancer (2). Patients who achieve axillary pCR are unlikely to benefit from ALND, which can result in surgical complications and long-term problems like lymphedema and restricted shoulder motion. A study by van Loevezijn AA and colleagues found that using the MARI-protocol, which involves marking axillary lymph nodes with radioactive iodine seeds to guide response-adjusted axillary treatment, allowed 80% of clinically node-positive (cN+) patients to avoid ALND. This approach achieved a 98% three-year axillary recurrence-free interval (aRFI) (28). In our study, none of the nine patients who underwent ALND after a positive SLN biopsy had received NACT.

To our knowledge, there is limited literature exploring patient satisfaction and experiences with Magtrace injection or comparing it to the conventional dual technique involving pre-operative Tc-99m injection and intraoperative BD application (3,29). Our findings reveal that patients in the Magtrace group expressed high levels of satisfaction. They valued the convenience of avoiding extra injections or appointments on the day of surgery. Additionally, they felt reassured by the supplementary appointment scheduled a week before surgery, which provided an opportunity to address any remaining concerns. Importantly, none of the patients reported feeling stressed about the additional visit.

Patients in the Magtrace group reported experiencing milder discomfort during injection compared to those in the Tc-99m group, with most patients in the Tc-99m group reporting no discomfort. This disparity may be genuine, as properly administered Tc-99m injections may not cause discomfort. However, the difference in reported discomfort could also be influenced by the timing of the questionnaire. Patients in the Magtrace group were surveyed sooner after their injection experience, with an average follow-up period of 4.8 months, compared to 9.9 months in the Tc-99m group. The recall of discomfort may be affected by the time between the operation and the questionnaire. Additionally, staining post-Magtrace injection was noted in 30% of cases, with 90% resolving within 6 months. In contrast, skin discoloration due to BD injection persisted for over 6 months in 35% of cases. Despite differences in staining, most women did not consider staining a cosmetic concern, and overall satisfaction with the injection process remained consistent across both groups.

Research by Wärnberg and colleagues in 2019 highlighted the significance of injection site, with 67.3% of periareolar and 37.8% of peritumoral injections developing skin staining (29). The rate of staining noted by Wärnberg was significantly higher than that observed by Lorek et al. (15%) and Rubio and colleagues (19%) (13,18). Magtrace was administered periareolarly to all patients in our study.

Approximately 20% of patients diagnosed with DCIS are discovered to have IBC upon definitive histology, often requiring further SLNB (17). The role of axillary staging in DCIS is debated, with no randomized trials providing clear guidance. Current guidelines advise against routine SLNB but suggest consideration in cases of planned mastectomy or in high-risk women undergoing breast-conserving surgery (BCS) (3,30). However, recent research indicates inconsistencies in existing guidelines for SLNB in DCIS, leading to significant practice variation. Karakatsanis et al. [2021] proposed refining these guidelines using novel techniques such as SPIO tracer to improve accuracy and reduce overtreatment (31). In this study, the sentinel node was marked by interstitial SPIO injection in the breast, but SLNB was not performed at the time of breast surgery. Delayed SLND was done only in patients with invasive cancer in the final surgical specimen. This approach would be feasible if the subsequent SLNB, is conducted within the 30-day window of Magtrace administration.

Despite the advantages of using Magtrace, there are notable disadvantages to consider. Alongside staining caused by accumulated SPIO, the presence of ferromagnetic metal residues in surrounding breast tissue has been found to diminish the image quality of post-operative breast magnetic resonance imaging (MRI) and rarely affect mammography and breast ultrasonography (31). This is particularly concerning for high-risk breast cancer screening populations where annual breast MRI is recommended. Efforts to address this issue include ongoing studies investigating the feasibility of breast MRI after SPIO application through adjustments in dose, volume, and application mode (32).

In one such study by van Haaren et al., the impact of SPIO induced artifacts on MRI imaging quality was investigated, and the potential of contrast-enhanced mammography (CEM) as an alternative for follow-up in breast cancer patients was explored (33). They discovered that even a small amount of SPIO tracer (1 mL) can impair the evaluation of breast MRI at the injection site beyond one year of follow-up. Another study by Man and colleagues reported that injecting 2 mL of SPIO tracer resulted in common post-operative MRI void artifacts and skin discoloration, which persisted for 18 months post-injection (33,34). However, no impairment was observed on full-field digital mammography (FFDM) and CEM, suggesting that CEM could serve as a reliable alternative to breast MRI if needed. Although allergic reactions were not reported in our patient cohort, it’s crucial to acknowledge that SPIO can cause such reactions, underscoring the importance of thorough patient inquiries regarding allergies, particularly to iron oxide or dextran compounds (35,36).

Based on the results of our study, we anticipate implementing several changes in our practice. Initially, to streamline clinic appointments, we aim to schedule Magtrace injections at the time of surgery consent, eliminating the necessity for an extra appointment. Moreover, to minimize skin discoloration, we will assess peritumoral injection as an alternative to retroareolar injection whenever feasible. Additionally, we will investigate the potential use of Magtrace in patients diagnosed with DCIS who are recommended to undergo SLNB.

Conclusions

The primary aim of our study was to evaluate and enhance the efficiency of operating theater scheduling, which prompted our investigation. We discovered that by using Magtrace instead of the conventional method, we could initiate our operating lists punctually, minimizing resource wastage and fully maximizing theater utilization.

Magtrace proves to be a practical alternative to the dual technique Tc-99m/BD for SLNB, particularly beneficial in settings where Tc-99m availability is limited, such as rural or underserved areas lacking nuclear medicine facilities. Implementation of Magtrace resolves scheduling challenges linked with Tc-99m and provides greater flexibility in injection timing, thereby enhancing operating theatre efficiency and reducing resource wastage. Moreover, Magtrace is well received by patients, showing minimal discomfort during injection and reduced duration of skin discoloration vs. BD. Despite its limitations as a small, retrospective study conducted at a single medical center, this study highlights the transformative potential of new SLN localization methods in reshaping breast cancer care towards a more efficient and patient-centered approach.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://abs.amegroups.com/article/view/10.21037/abs-24-23/rc

Data Sharing Statement: Available at https://abs.amegroups.com/article/view/10.21037/abs-24-23/dss

Peer Review File: Available at https://abs.amegroups.com/article/view/10.21037/abs-24-23/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://abs.amegroups.com/article/view/10.21037/abs-24-23/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). This study was approved by the ethics committee of Cwm Taf Morgannwg University Health Board and individual consent for this retrospective analysis was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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