Introduction

In breast cancer surgery, investigation of the status of axillary lymph node (ALN) is a pivotal prognostic factor that determines the next course of treatment for the patients. Axillary lymph node dissection (ALND) has been considered as a gold standard for postoperative pathological staging in invasive breast carcinoma. However, this process involves substantial morbidity such as paresthesia and arm numbness, lymphedema, and limited shoulder movement, which adversely affects the patient’s quality of life (1, 2). Hence, there is a paradigm shift in the surgical management of ALNs that evolved from complete axillary lymphadenectomy to a more conservative approach of axillary dissection. Eventually, the introduction of the sentinel lymph node biopsy (SLNB) in carcinoma breast surgery has revolutionized the pathological assessment of ALNs in early breast cancer patients. This method has minimized the occurrence of debilitating adverse events in post-operative patients caused by complete ALND (3). Hence, SLNB has been practiced widely as the standard procedure for axillary staging in early breast cancer patients (4–6).

There are various tracer techniques employed to perform SLNB, and each has its own limitations and advantages. Some surgeons prefer to use radioisotopes (RI) or vital dyes alone, whereas others prefer dual tracer-guided SLNB. However, the major limitations of radioactive tracer techniques are their high cost, technical complexity, and logistics (7). Furthermore, this technique requires a highly specialized and state of-the-art department of nuclear medicine capable of handling RI sat the point-of-care unit, but most of the public tertiary care centers in developing nations lack this facility. Furthermore, the chance of radiation exposure to the patient and treating surgeon is another significant challenge in the use of radioactive colloid. Hence, the use of diagnostic dyes for SLNB is a viable alternative technique to RI-based methods. Despite the availability of different dyes such as patent blue (PB), isosulfan blue, and indocyanine green, methylene blue (MB) is widely used due to its cost effectiveness and easy availability. Besides, the use of the MB technique alone is practiced more in SLNB these days due to its technical ease of use and lesser chances of anaphylaxis and/or tissue necrosis compared with other dyes (8–10). Despite the wide acceptability of MB in SLND, some surgeons reported quick diffusibility of the dye into the peripheral tissues, which stains a large portion of the breast, thereby affecting the surgical procedure to some extent (11– 13). Similarly, few authors reported varying sensitivity, specificity, sentinel lymph node (SLN) identification rate, and false-negative rate (FNR) of MB dye in SLNB (14–17). It is therefore imperative to validate this economic and cost-effective SLNB technique to increase usage in public healthcare settings in developing nations like India. Hence, the objective of this study was to assess the accuracy of this tracer technique (using MB alone) in clinically and radiologically node-negative breast cancer patients.

          

 

Patients and Methods

This study was approved by the institutional ethics committee of Acharya Harihar Regional Cancer Centre, Cuttack, Odisha, India(letter no. 102-IECAHRCC).From January 2018 to February 2020, patients with early invasive female breast cancer (stageT1– T3,N0, M0) with clinically and radiologically nodenegative axilla were included prospectively in this study (n=43).Of 51 identified patients, 3patients with progressive disease with skin involvement and 5 patients in whom SNLs could not be identified were excluded (Figure 1).The details of the 5 cases where SNLs could not be identified are given in Table1. The small sample size precluded any statistical conclusion. Patients with previous breast cancer surgery or axillary dissection, neoadjuvant therapy, distant metastasis, or any palpable or radiologically detected axillary nodes were excluded from the study. Patients with T4 or larger tumors, with inflammatory breast cancer, who were pregnant females, or with male breast cancer were also excluded from this study. Similarly, patients with any scar of previous surgery within the natural pathway of lymphatic drainage that blocks the lymphatics going toward axilla were not included. Patients who received radiation therapy to the chest wall for any other reason, and patients unwilling to participate in the study were also excluded.

In this research, five experienced surgical oncologists participated, and the surgeries were performed after obtaining informed consent from the patients. The surgeries were performed as per standard protocol (18– 20), with minor modifications. Briefly, routine preoperative assessment of surgical fitness, chest radiography, and ultrasonography was performed for all the enrolled patients. Before approximately 15 to 20 minutes of the surgery or immediately after the induction of anesthesia, 1% MB dye (3–5 mL based on breast volume) was injected in two equally divided doses. Half of the dose was administered in the peritumoral region close to the axilla, while the other half was administered to the periareolar site. Postinjection, for 2 to 5 minutes, gentle message was performed laterally to the tumor to prevent the migration of malignant cells to regional lymph nodes and to facilitate the movement of the MB dye. Mastectomy or lumpectomy was performed with standard principles, and then, the axilla was exposed. The axilla was accessed by a separate axillary incision, and the lateral and anterior skin flaps were raised, up to the angular vein, as in standard methodology in the case of breastconserving surgery planning. When modified radical mastectomy was planned, the axilla was accessed through the same incision after raising the skin flaps laterally and anteriorly. Starting from the axillary tail of Spence, the blue lymphatics were searched and traced toward the nearest node. Then, the lymph nodes in the axillary tail; pectoral, central, lateral, and posterior groups; and interpectoral and apical nodes were searched meticulously in situ for blue-stained ones. Simultaneously, the axilla was palpated during surgery for the presence of any suspicious nodes (nodes >1cm or with rounded shape) harboring metastatic disease. The nodes that stained blue completely or partially (Figure2 VI, VII) and suspicious nodes were considered as SLN and were harvested. Furthermore, level I and II nodal dissection were done, followed by level III lymphadenectomy, and sent for histopathology in separately labeled containers. Hematoxylin and eosinstained slides of SLNs and all ALNs were carefully studied and compared for the presence or absence of metastasis.

The surgical plan was made on clinical grounds of operability, that is, disease stage and immunohistochemistry (IHC) were not considered in the pre-operative decision making and, thus, were not considered in our study.

Our study aimed to validate the technical methodology for surgeons based on clinical grounds; thus, IHC was not included. To determine the effects of IHC on SLN technique, various factors would be compared with IHC, which requires multivariate analysis with a large number of sample size and will provide a completely different study direction.

   

 

Results

Between January 2018 and February 2020,51 cases were identified, of which 3cases were excluded from the study, as discussed in the previous section. From the remaining 48 subjects, SNLs could not be identified intraoperatively in 5 cases; hence, the SNL identification rate in our study was 89.6% (Figure 1). The mean age of the patients in the studied cohort was 49.58 years, with minimum and maximum age of 32 and 69 years, respectively.

The clinicopathological investigation revealed6 (14%), 20(46.5%), 12(28%), and 5(11.5%) patients with stage I, IIA, IIB, and IIIA, respectively. In our study, SNLs were found at level I of the axilla in 40 cases (93%), at level II of the axilla in 2 cases (4.7%), and at levels I and II of the axillary region in 1 case (2.3%). In this investigation, the mean number of SNLs and ALNs harvested per subject was 2.88 and 14.23, respectively. Furthermore, in the interventional study, a total of 614 lymph nodes were harvested, of which 124 were SNLs and 490 were non-SNLs. In addition, 24 (19.3%) of 124 SNLs were positive, 13(2.6%) of 490 non-SNLs were positive, and 4(0.8%) skipped metastatic ALNs (in one patient). The rest of the clinicopathological findings are presented in Table 2.

In this MB-guided SLNB technique, 13 cases were true positive (a), 29 cases were true negative (d), and 1 case was false negative (c). Hence, the sensitivity, specificity, FNR, and accuracy of our studied technique were92.8%, 100%, 7.14%, and 97.7%, respectively (Table 3).

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Click to view Figure 1: Patients included and identification rate

Click to view Figure 2: Site of Methylene Blue injection and harvested sentinel lymph node

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Discussion

In the recent past, there is a paradigm shift in the surgical management of early breast carcinoma. Conservative surgery with SLNB has become a regular practice by surgical oncologists for axillary staging (21,22). Giuliano et al. (18), in 1994, first introduced this technique for axillary lymphatic mapping and lymphadenectomy in breast carcinoma, which has a sensitivity and specificity of 88.0%, and 100%, respectively. Since then, this axillary staging procedure, which has less morbidity, has been practiced and evaluated by different groups of surgeons.

As we discussed in the previous section, diverse tracer techniques, such as radioactive isotopes, vital dyes, and dual-tracer technique, are currently widely used in SLNB. Although dual-tracer techniques have been the gold standard for localizing the SLNs (23,24), the unavailability of nuclear medicine department in many public tertiary care centers and expensive vital dyes have prompted wide use of MB (8–10). However, the SNL identification rate, sensitivity, specificity, FNR, and accuracy of the tracer technique (using only MB) are of paramount concern.

In a recent study, Özdemir et al. (19) reported a sensitivity of 85%, specificity of 100%, identification rate of 94%, FNR of 15%, and accuracy of 93%of the MB technique. Similarly, Nandu and Chaudhari (20), in 2017, reported the sensitivity, specificity, FNR, and accuracy of MB technique in SLNB as 90.48%, 85.71%,9.52%, and 88.57%, respectively.

Our present study revealed the sensitivity, specificity, FNR, and accuracy of MB-guided SLNB as 92.8%, 100%, 7.14%, and 97.7%, respectively. The sensitivity found in our study is higher than the sensitivity reported by Özdemir et al. (19) and Nandu and Chaudhari (20). Furthermore, our specificity is equal to the specificity achieved by Özdemir et al. (19).

In a recent randomized controlled trial, the dual-tracer technique was employed, where all patients received radionuclide tracer in the peritumoral region and were randomized to MB and PB groups. In this study, the results (SLN identification rate and FNR) in the MB dual-tracer group (97.4% and 1.49%, respectively) were significantly better than those obtained in the PB dualtracer group (96.6% and 3.39, respectively) (p>0.05). Hence, considering the cost-effectiveness and easy availability, wider use of MB is recommended for lowresource facilities (25).

The total cost for MBin the whole study for all 43 patients was 210INR (3 USD). A 5-mL syringe was used in each patient, which costs around 5 INR each, for a total of 215INR. The total cost of the whole study for 43 patients is approximately 425 INR (6 USD). The cost per patient in this study was approximately 10 INR (0.14 USD). There was no significant increase in the duration of surgery or anesthesia; hence, no extra cost was added to these parts.

Additionally, the dual-tracer technique seems beneficial for less experienced surgeons and in cases where the chances of FNR and misidentification of SLNs are high, such as in patients in neoadjuvant therapy, those who had prior breast or axillary surgery, and those with obesity. Hence, the blue dye tracer technique seems ideal for patients with node-negative early breast cancer. In one landmark study, Krag et al. (5), in 1993, reported 82% of SLN identification rate using only RIand γprobe; meanwhile, in our study, we report a superior identification rate of 89.6% using only MB. Furthermore, Li et al. (26), in a prospective study, used 99mTc-rituximabradiotracer alone to perform SLNB. They found the sensitivity, specificity, and accuracy of the method as 97.4%, 100%, and 98%, respectively, which were similar to the results of our present study (using MB only).

The FNR observed in our study (7.14%) was lower than those of the two aforesaid studies. Additionally, the FNR of our study is almost equal to the average FNR of 69 trials (7.3%) reported by Kim et al. (23).

As we discussed in the previous section, the use of RI has a diverse logical challenge, starting from the infrastructure to the handling of the RI, staff training, isotope disposal, and legislative concerns. The schedule of the surgeries is restricted due to the short half-life (6 hours) of the RI, and the injection has to be administered by the nuclear medicine experts. Furthermore, radiation exposure is possible. Hence, the use of a single dye tracer, most preferably MB, is commercially more viable than other dyes and RIs.

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Conclusion

Institutions should have a validated SLNB technique when using a single-agent dye and such technique should have a low FNR that is within acceptable range. It may take training and revision of technique to achieve a low FNR. Our technique uses MB dye along with intraoperative palpation method after meticulous dissection of lymph nodes in each level. Our study provides a detailed methodology and different modifications to the standard technique of using a single-agent MB with acceptable time and easy transfer of knowledge among residents and other surgeons. Such validation studies will help trainee surgeons and surgical residents to start similar validation methods in various surgeries other than breast surgery.

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Acknowledgement

The authors would like to thank the team of Indquench Life Science Innovations (OPC) Pvt., Ltd., and Prof. Padmalaya Devi, Dr. Swadeep Mohanty, and Dr. Subhrat Samantara of Acharya Harihar Post Graduate Institute of Cancer for their constructive comments, peer review, and support to develop this manuscript.

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