Breast Conserving Surgery Guided with Magnetic Seeds vs Wires: la Paz University Hospital Experience

doi:10.21203/rs.3.rs-2233662/v1

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Breast Conserving Surgery Guided with Magnetic Seeds vs Wires: la Paz University Hospital Experience

https://doi.org/10.21203/rs.3.rs-2233662/v1

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Background: In recent years, there has been an increase in breast surgery for nonpalpable lesions. Traditionally, wires have been used to guide the resection of nonpalpable breast tumors. Recently, several devices have been commercialized as alternatives to classical wires, such as magnetic seeds (Magseed®). The aim of this study is to describe our initial experience using magnetic seeds (Magseed®) to guide breast-conserving surgery in nonpalpable breast lesions and compare the use of magnetic seed with wires to guide breast-conserving surgery, in terms of clinical and pathological characteristics.

Methods: We performed a retrospective study including all breast-conserving surgeries for nonpalpable breast lesions <16 mm, from June 2018 to May 2021. We compared breast-conserving surgeries guided with magnetic seeds to those guided with wires, analyzing: tumor, and patient characteristics, surgical time, and pathological results of the surgical specimens.

Results: Data from 225 cases was collected, 149 magnetic seeds and 76 wires. The breast lesion was localized in every case. Both cohorts were similar regarding clinical and pathological characteristics. We found significant statistical differences (p <0.02) in terms of the median volume (cm3) of the excised specimen, which was lower (29.3%) in the magnetic seed group compared with the wire group (32.5 [20.5-60.0] / 46.0 [20.3-118.7]). We did not find significant differences regarding surgical time (min), and affected or close margins.

Conclusion: In our experience, the use of magnetic seed (Magseed®) is a feasible option to guide breast-conserving surgery of non-palpable lesions and enable us to resect less breast tissue.

breast cancer

nonpalpable

breast-conserving surgery

wire

magnetic seed

In recent years, due to screening programs, and the increasing use of neoadjuvant therapy, there has been an increment in breast surgery for nonpalpable lesions(1). Breast-conserving surgery (BCS) is acquiring major acceptance, as there is evidence that demonstrates that mastectomy has no survival benefit over BCS plus radiotherapy(2). Traditionally, wires have been used for guiding nonpalpable breast tumor resections (1). Wires present several disadvantages, such as displacement, migration, retained fragments, patient discomfort, and difficulties in surgical scheduling, as they must be placed prior to surgery. Another limitation is the site of wire insertion, which is normally placed where it is easier for the radiologist and does not consider the surgeon´s cosmetic surgical approach. For surgeons wires present an important disadvantage in the surgery room, as surgeons have to mentally plan the surgical approach by visualizing the mammogram with the consequent breast tissue compression, since it is not possible to localize the wire prior to opening the skin. All previously mention factors contribute to difficult the localization of non-palpable tumors intraoperatively and may cause increased breast volume resection.

Recently, several devices have been commercialized as alternatives to the classical wires, such as the Magseed® (MS) magnetic seeds. The use of MS to guide the resection of nonpalpable breast lesions presents many advantages, such as: precise surgical guiding, less discomfort for patients, and it facilitates surgical scheduling, as the seed can be placed days prior to surgery(3).

The aim of this study is to describe our initial experience using MS to guide BCS for nonpalpable breast lesions, as well as, to compare our experience using MS with wire-guided BCS in terms of clinical and pathological characteristics.

We performed a single institution retrospective study including every patient that underwent BCS for nonpalpable tumors \(<\)16mm, from June 2018 to May 2021 at La Paz University Hospital. Previous ethical approval was obtained, and every patient signed an informed consent before being included in the study. The first MS were placed in June 2018, and for several months we used either wires or MS to guide breast surgery for nonpalpable breast lesions, depending on the radiologist preference, the availability of MS, and the surgical scheduling.

Both wires and MS were placed by four experienced breast radiologists under ultrasound or mammogram guidance, depending on the characteristics of the breast lesion, using local anesthesia. A control mammogram was performed after placing the wire or the MS in all cases and could be visualized during the procedure in the surgery room (Fig. 1). Wires were placed the same day of the surgery, and MS were placed independently of the surgery day, always less than 30 days before surgery, as MS were initially approved for placement up to 30 days prior surgery (although, currently MS has no limit regarding the time between surgery, and its placement). MS were localized intraoperatively using the Sentimag® probe. Every surgical specimen, including wires, and MS guided specimen, was evaluated with mammogram to confirm adequate excision of the lesions (Fig. 2).

Data was retrospectively collected, including: age, body mass index (BMI), menopausal status, histological type, grade, hormone receptor status, her-2 status, ki67, tumor phenotype (St Gallen 2013), surgical guidance technique, primary treatment (surgery or neoadjuvant treatment, either chemotherapy or hormonotherapy), radiological tumor size, surgical time, total volume of the surgical specimen (specified in the pathological report), margin status, and possible re-excision. Surgical specimen margins were categorized into three groups: free, close margins (< 2mm), and ink touch group.

We compared BCS guided with MS with those guided with wires, performed from June 2018 to January 2019, when we stopped using wires. We conducted a descriptive analysis of the data collected. Categorical variables were described as frequency or percentage. Continuous variables were reported as the median and interquartile range (IQR). A comparison of characteristics among variables was performed using the most appropriate test. The type 1 error rate (ⲁ) was set to 0.05. Statistical analyses were performed using SPSS v26 (IBM Corporation, Armonk, NY). We used the STROBE cohort reporting guidelines

A total of 225 patients that underwent BCS for nonpalpable breast lesions were included in the study, 149 surgeries were MS-guided, and 76 were wire-guided. No incidence during placement of MS or wires was reported, being accurately placed in all cases either centrally or laterally to the lesion. The tumor was localized and excised in every case. In 6 cases, 2 MS were placed to guide excision, in 4 cases to mark 2 coils placed prior to neoadjuvant treatment, and in 2 patients to delimit an area of microcalcifications with confirmed diagnosis of intraductal carcinoma (Fig. 3). Both cohorts were similar regarding clinical and pathological characteristics: patient age, menopausal status, body mass index, histological type, histological grade, tumor phenotype, tumor size per image (mm), and initial treatment (surgery, neoadjuvant treatment: chemotherapy or hormonotherapy) (Table 1).

The mean radiological size of the breast lesions was 8mm (range 0-16mm), with no statistical difference between the MS and the wire group. In 57 cases (35 MS, and 22 wires), no residual tumor was localized radiologically after neoadjuvant chemotherapy, consequently, the MS or the wire were placed in the marking coils for guiding excision of the tumor bed.

The median volume of the surgical specimen was 32.5 cm³ (20.5–60.0) in the MS group, and 46 cm³ (20.3-118.7) in the wires group, with a statistically significant difference (p < 0.02). The median surgical time was 92 min (range 45–200), and 100min (range 40–260), in the MS and wire group, respectively (p = 0.17). Several patients underwent unilateral or bilateral oncoplastic procedures after the surgical removal of the tumor, consequently extending surgical time.

Free margins were obtained in 91% (n = 136) of the MS, and 94% (n = 72) of wires. 17 patients of all the patients included in the study underwent re-excision (7,5%), 4 cases in the wires group (5,4%) for close margins, and 13 cases in the MS group (8,7%), 9 for close margins, and 4 for ink touch. When comparing close margins, no statistical difference was found between both groups (p = 0.34) (Table 1).

Table 1

Patient and tumor characteristics. ¹ Magnetic Seed (Magseed®)
		MS¹	Wire
n		149	76	p
Age (years)	median (range)	65.0 (28–85)	60.0 (39–90)	0.60
Menopausal Status	premenopausal	45	18	0.30
Menopausal Status	postmenopausal	104	58	0.30
BMI	median (range)	25.2 (17.72–39.66)	24.5 (16.85–41.65)	0.32
Histological Type	Ductal	107	55	0.75
	Lobular	12	5
	In situ	16	11
	Others	14	5
Differentiation Grade	G1	37	16	0.53
	G2	66	38
	G3	43	22
	unknown	3	0
Tumor Phenotype	Luminal A	62	21	0.49
	Luminal B	27	16
	Luminal B Her2	16	11
	Her2	12	7
	Basal	15	9
Tumor Size per image (mm)	median (range)	8 (0–16)	8 (0–16)	0.64
Focality	Unifocal	138	66	0.16
Focality	Multifocal-Multicentric	11	10	0.16
Initial Treatment	Excision	82	35	0.06
	neoadjuvant endocrine therapy	27	9
	neoadjuvant chemotherapy	40	32
Surgical Time (min)	median (range)	92 (45–200)	100 (40–260)	0.17
Volume of the excised specimen (cm³)	median (range)	32.5 (20.5–60.0)	46,0 (20.3-118.7)	0.02
Margins	Free	136	72	0.34
	Close (< 2 mm)	9	4
	Touch ink	4	0

MS have demonstrated its feasibility and non-inferiority compared to wires for guiding BCS in nonpalpable breast tumors(4). Moreover, MS have proved to present several advantages over wires. One of the key advantages of MS is the possibility of dissociating placement, and surgical timing, consequently facilitating surgical scheduling(5). We found that independent radiologist and surgeons programming made surgical scheduling much more efficient, as the placement of wire prior to surgery delayed surgery timing, being one of the main reasons for which we substituted wires for MS.

We successfully reported placement of the MS in the lesion, either centrally or laterally, as well as, detection of the MS, and excision of the lesion in every case. No complications were registered during MS placement or excision. We have also used MS for bracketing breast lesions, with good results. In conclusion, it can be stated that the MS technique presents a short learning curves for radiologists and surgeons, in agreement with other studies(5) (6). Although, it must be considered that our multidisciplinary breast unit diagnoses, and treats over 360 breast cancer per year, and the MS were placed by four breast radiologists with a broad experience in wire placement and excised by six experienced breast surgeons. Therefore, the learning curve may not be reproductible in every unit, and may depend on the experience of radiologists, and breast surgeons.

The strength of our study is the finding on the surgical specimen volume. To our knowledge, only one article has demonstrated a statistical difference in terms of the size of the surgical specimen when comparing guiding techniques. Micha et. al. found that the surgical specimens weight was smaller in the BCS group guided with MS than wires, with a statistically significant difference (7). We measured volume (cm³) instead of weight, finding smaller surgical specimens when MS was used for guidance compared to wires, being this difference statistically significant. It has been demonstrated that when resecting breast tissue, excising smaller volumes leads to better cosmetics results, as the breast defect is reduced (8). Although, a recent review concludes that there is no evidence that MS reduce surgical specimen volume, our findings, along with further studies, may change this assumption in the near future (4).

Cosmetic outcomes are not only determined by the volume of the surgical specimen, but it is also negatively influenced by possible re-excision procedures, and the increase in scar length(9). Re-excision rates for MS have been reported in the literature ranging from 11.2 to 21,9%(10). Gera et. al. published a re-excision rate of 11,25% in a pooled analysis that included 1559 MS procedures (4). We present a low re-excision percentage, although no statistical difference was found between MS and wires. In addition, while we resected smaller breast volume in the MS group, no increase in close and/or positive margins was found; thus, there were no more re-excision procedures in this group.

Another important advantage that we found when we started to use MS was that it can be localized with the Sentimag→ probe before skin incision, making it possible to design the surgical approach, reducing breast dissection, and scar length, contributing to obtaining better cosmetic results. Possibly, the capability of designing the surgical approach before the incision is performed has contributed to reduce del surgical specimen volume.

Surgical time was very variable, ranging from 90 to 200 min, and 90 to 260 min in the MS group and the wires group, respectively, not finding a statistical difference. This time range can be explained because some patients underwent unilateral or bilateral oncoplastic surgeries to assure good cosmetic results at the expenses of extending surgical time.

The most important drawback that MS present is the cost, as they are much more expensive than wires, but we ought to consider that overall cost can be reduced by more efficient surgical, and radiological timing. However, further research in cost-efficiency is needed(11).

The main limitation of our study is that it is a single-institution retrospective observational study. Although we are not the first to find smaller surgical specimens after BCS guided with MS, further studies, ideally multi-center prospective randomized trials are needed to confirm these findings.

In conclusion, in our experience magnetic seeds (Magseed®) enables us to perform less extensive resections in BCS, which means better cosmetic results with comparable oncological results. We also find that magnetic seeds facilitate hospital logistical organization in terms of pairing-up radiology and surgery departments.

BCS Breast-Conserving Surgery

MS Magnetic Seed

BMI Body Mass Index

Ethics Approval

The study was approved by the Ethics Committee of La Paz University Hospital CEIm (Comité de ética de la Investigación con Medicamentos del Hospital Universitario de la Paz) (Register number PI-5437 (2022.546)).

Consent for publication

Not applicable.

Data availability

The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.

Competing interest

The authors declare that they have no competing interest.

Funding Statement

The authors received no financial support for the research and authorship of this article.

Authors Contribution

VC, MJR y JMO placed the wires and magnetic seeds, and recollected radiological data. EM, JM, MM, CM, LF, AL y AH performed the breast surgery guided with wires or magnetic seeds, and recollected the data. EM and JM analyzed the data and wrote the manuscript. All authors read and approved the final manuscript.

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No competing interests reported.

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Breast Conserving Surgery Guided with Magnetic Seeds vs Wires: la Paz University Hospital Experience

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