Abstract
Background/Aim: The aim of this study was to evaluate the current role of frozen section in identifying patients who could benefit from an immediate axillary lymph node dissection (ALND), following the criteria of the ASOCOG Z0011 and IBCSG 23-10 trials. Patients and Methods: A retrospective review was performed involving 2,079 patients with early breast cancer who underwent conservative surgery or total mastectomy with sentinel lymph node biopsy. Results: Sensitivity and diagnostic accuracy were 63.8% and 90.3%, respectively. Sensitivity was significantly higher (p<0.001) in finding macrometastases (81.8%) compared to micrometastases (11.9%). Frozen section was useful only in 7.7% of the patients who met the criteria of the IBCSG 23-01 and ACOSOG Z0011 trials. Conclusion: Frozen section continues to be very useful in the intraoperative assessment of the SLN, offering a high sensitivity and diagnostic accuracy. Omission of ALND in 24.4% of patients who met the ACOSOG Z0011 criteria would have resulted in their undertreatment.
Sentinel lymph node biopsy (SLNB) is currently considered the standard of care for axillary staging in patients with clinical lymph-node negative breast cancer, limiting the use of axillary lymph node dissection (ALND) only to patients with metastatic sentinel lymph node (SLN) (1, 2).
Intraoperative frozen section (FS) of SLN, such as other intraoperative methods of assessment, has the advantage to proceed immediately to ALND in patients with positive SLN avoiding a second axillary surgery which, in addition to being more complex and time-consuming, could result in greater risks in terms of anaesthesia and postoperative complications, higher hospital costs and cause considerable discomfort to the patients. FS is the most widely used method in the intraoperative assessment of SLN. In many studies, it has shown a high specificity (98-100%) and, even if the sensitivity is variable from 41 to 91% (3-12), it reduces the risk of a deferred ALND in a non-negligible percentage of patients (10).
The indications to carry out an ALND in case of positive SLN have been further revised according to the American College of Surgeons Oncology Group Z0011 trial (ACOSOG Z0011) and the International Breast Cancer Study Group 23-01 trial (IBCSG 23-01), that started in the late 1990s and in 2001, respectively. Based on the evidence that many breast cancer patients with positive SLNs do not have additional metastatic lymph nodes at the ALND, ACOSOG Z0011 trial randomized patients with T1 to T2 tumours and 1 to 2 positive SLNs who underwent breast conservative surgery with whole-breast irradiation to either complete the ALND or to not undergo any further axillary surgery. The 10-year outcome of the trial showed no differences in overall survival between the patients treated with ALND and those treated with SLNB alone, with less morbidity shown for the latter patients (13, 14). Subsequently, the results of the IBCSG 23-01 randomized trial showed that after 10-years follow-up, ALND can be safely omitted in T1 to T2 breast cancer patients with SLN micrometastases (15, 16).
At our institution, the great majority of SLNs are still sent for intraoperative FS. However, in light of the results of these two trials, which practically further reduce the indications for ALND in patients with positive SLNs, a review about the utility of intraoperative FS was considered necessary.
The aim of this study was to confirm the validity of intraoperative FS in the detection of SLN metastases and its usefulness in identifying patients who would have actually benefited from an immediate ALND, based on the criteria of the two trials.
Patients and Methods
After approval by the Institutional Review Board of the University Hospital AUOP Paolo Giaccone of Palermo, the records of 2079 patients, who underwent surgery for invasive breast carcinoma at our Institution in the period between January 2007 to June 2019, were retrospectively analysed. A total of 1456 patients with primary invasive operable breast cancer and clinically axillary negative lymph nodes were considered eligible for the study. All patients underwent conservative surgery or total mastectomy with SLNB; intraoperative FS of SLNs was routinely performed.
A bilateral synchronous infiltrating breast carcinoma was diagnosed in 21 patients. In 14 of the 21 patients, a bilateral SLNB was performed, while in seven patients a contralateral elective ALND was performed because of the pre-operative diagnosis of fine needle aspiration cytology positive-proven axillary nodes. Totally, 1470 intraoperative FSs of SLNs were performed.
Exclusion criteria of the study included a precedent neoadjuvant chemotherapy, a diagnosis of inflammatory breast cancer, locally recurrent breast cancer, pregnancy and proven allergy to the contrast agent and/or to the vital stain.
Preoperative diagnosis of infiltrating breast carcinoma was achieved by means of fine needle aspiration cytology and/or by percutaneous needle core biopsy of the breast lesions. Preoperative evaluation of the axillary lymph nodes was made by means of the clinical and ultrasound examination of the axilla. If suspicious axillary nodes were discovered, they were biopsied with an ultrasound guided fine needle biopsy. Criteria to define suspicious lymph nodes included cortical thickness ≥3 mm, focal or eccentric cortical thickening and an abnormal or absent clear hilum.
Lymph nodes mapping and operative technique for SLNB. All patients underwent a preoperative lymphoscintigraphy by means of a subdermal periareolar injection of 99Tc-labeled human albumin colloid (10-12 MBq di Tc-99m in 0.2 ml of albumin colloid), 18-24 hours before surgery (4, 17). SLN was identified by obtaining in the gamma chamber scintigraphic images 15, 30, and 180 min after the administration of the radiotracer and the cutaneous projection of SLN was marked with indelible ink for identification. For the intraoperative identification of the SLN, a radio-guided surgical probe (Neoprobe Gamma Detection Systems®, Cincinnati, OH, USA) was used. Limited to the cases were the radio-guided surgical probe detected a weak radiotracer signal, a subareolar injection of 0.5-0.8 ml of vital stain about 10-15 minutes before surgery was performed. All hot and/or blue lymph nodes were removed and submitted immediately to FS. Subsequently, the probe was also used on the operated piece to confirm the presence of radioactivity.
Failure of detecting at least one coloured and/or warm lymph node was considered a failure of the method and an immediate ALND was electively performed.
Pathological examination. Nodes with a diameter of more than 5 mm were bisected longitudinally and frozen. SLNs with a diameter of less than 5 mm were frozen intact. Intraoperative examination was carried on two 4 μm frozen sections stained with hematoxylin and eosin (H&E). The time needed for the procedure was of 15-20 min. All the remaining tissue was formalin-fixed, paraffin-embedded and entirely sectioned at 100-micron intervals for the definitive histopathological examination. Three seriated sections were obtained at each step and one of them was stained with H&E. Immunohistochemical assay was performed on the remaining seriated sections, by using the monoclonal antibody for pancytokeratins AE1/AE3 (Dako, Santa Clara, CA, USA) and the avidin biotin peroxidase complex method, when the result from the H&E sections was ambiguous. If more than one SLN was obtained from a patient, all the nodes were examined through this procedure. The presence of neoplastic cells was classified as micrometastases (≤2 mm), macrometastases (≥2 mm); single tumor cells or small clusters of cells (<0.2 mm) were defined as isolated tumor cells (ITC).
Tumour features (1,470 tumours).
Surgical procedure. All the patients underwent synchronous excision of the breast cancer either by conservative surgery or total mastectomy and SLNB. The excision of any non-SLNs was performed only in cases where clinically suspected lymph nodes were present at the intraoperative palpation of the axilla. All patients with SLN macro-metastasis at FS underwent immediate completion ALND. In the cases of SLN negative at FS but positive for macrometastases after the histopathological examination, patients underwent a delayed completion ALND. No completion ALND was performed in women with metastasis-free SLN. In patients with SLN micrometastases, either at intraoperative or at final histopathological examination, a total ALND was performed up to 2009; from 2010 onward, in these patients no further treatment on the axilla was performed.
Relation between pathological tumor size and SE and DA of FS.
Statistical analysis. Comparisons were assessed using the X2 test or the Fisher exact test, depending on the sample size. Values were considered statistically significant when p<0.05. The sensitivity (SE) and diagnostic accuracy (DA) were calculated with the following formulas: sensitivity=true positive/(true positive+false negative) and accuracy=(true positive + true negative)/total number.
Results
In the period between January 2007 and June 2019, 1470 SLNBs were performed at our Institution, on 1,456 breast cancer patients included in this study.
The mean age of the patients was 58.7 years (range=28-72 years). The pathological characteristics of the tumours and the type of the surgical interventions performed are summarized in Table I.
In four cases (0.27%), SLN was not identified intraoperatively, so an immediate ALND was performed. In the 1,466 cases in which SLN was successfully identified, a mean number of 2.1 (range=1-11) SLNs were removed.
At intraoperative FS, SLNs were negative in 1215 cases (82.9%), two among these were ITC, whereas macrometastases were found in 239 cases (16.3%) and micrometastases in 12 cases (0.8%). The definitive histopathological examination of the SLNs confirmed the absence of metastases in 1,073 cases (88.3%) while macrometastases were found in 48 cases (3.9%) and micrometastases in 94 cases (7.7%). The overall false negative (FN) rate was 11.7% (142/1215 cases). No false positives cases were found at the definitive histopathology.
SE and DA of the FS examination of SLNs were 63.8% and 90.3%, respectively. However, considering the SE of the FS separately for the detection of micrometastases and macrometastases, it was significantly higher (p<0.001) in finding macrometastases (81.8%) compared to micrometastases (11.9%). SE and the DA of the FS by tumor dimensions and histologic type, summarized in Table II, show significant correlation (p<0.01) between tumor size and FS sensitivity, while no significant correlation between histologic type and FS sensitivity was found.
All the 239 patients with SLN macrometastases at the intraoperative FS underwent an immediate completion ALND, while only 4 of the 12 patients with SLN micrometastases at the intraoperative FS underwent an immediate completion ALND (these 4 patients were operated before 2010).
With regard to the 142 patients with a false negative result at the intraoperative FS, a delayed completion ALND was performed in 11 of the 94 patients with SLN micrometastases (these 11 patients were operated before 2010) and in 45 of the 48 patients with SLN macrometastases. In 3 of these latter patients the decision to omit a completion ALND was taken in agreement with the patients, considering that 2 to 5 non-SLNs excised during the SLNB were found negative at the definitive histopathological examination.
Overall, 299 ALNDs were performed, and in 243 (81.3%) cases the use of FS avoided a second axillary surgery.
The results of the histopathological examination of the axillary lymph nodes excised at completion ALND are resumed in Table III. In 54.5% of the patients who underwent ALND no further involved lymph nodes were found at the final histopathological examination.
All the data described above have also been interpreted considering the criteria of the IBCSG 23-01 and ACOSOG Z0011 randomized trials.
One hundred and six patients met the IBCSG 23-01 trial criteria (tumour size <5 cm, SLN positive for micrometastases), 91 of these did not undergo any further treatment of the axilla, while 15 patients (14.1%), treated before 2010, underwent completion ALND. In these latter patients, a single axillary macrometastatic lymph node was found only in one case (6.6%).
Results of completion ALND in patients with positive SLN.
Patients who underwent ALND after positive SLNB.
Totally, 172 among the 287 (59.9%) patients who were SLN positive for macrometastases, met the criteria of the ACOSOG Z0011trial (T1-T2 tumours, 1-2 SLN positive for macrometastases, conservative surgery followed by whole breast irradiation); 143 of these were positive at the intraoperative FS, while 29 were false negative. In 56.9% of the patients (98/172), no further involved lymph nodes were found at the final histopathological examination, however it was remarkable that in 24.4% of the patients (42/172) three or more positive axillary lymph nodes were found at the final histology (Table IV).
Intraoperative FS was useful in 16.6% of the patients (243 true positive/1,466 SLNB) avoiding a delayed ALND in 81.3% of the patients with positive SLN (243/299 patients). This percentage would have dropped drastically to 7.7% if the criteria of the IBCSG 23-01 and ACOSOG Z0011 trials were applied. Nevertheless, in about a quarter of these patients, omitting ALND could have been an undertreatment.
Discussion
Intraoperative examination of SLN has the advantage to proceed immediately to ALND in patients with positive SLN avoiding a further axillary surgery. FS remains the most used method of intraoperative assessment of SLN. In fact, despite the specificity of both the FS and the intraoperative cytology approach, FS shows a greater sensitivity than intraoperative cytology, and can also provide information on the size of the metastases (10, 18, 19). However, FS has some limitations including that it is an expensive and time-consuming procedure, requires an experienced pathologist (18), and the process of preparing a frozen section increases the risk of destroying the diagnostic tissue significantly (20).
In this study, a high SE and DA of intraoperative FS have been recorded, which were 63.8% and 90.3% respectively, substantially consistent with the findings of one of our previously published articles (3) and with those reported in literature (21-26). In particular, SE was higher in T2 and T3 tumors than in T1 tumors (p<0.001), similar to the results of other authors (21, 22), while no significant correlation between histologic type and SE of FS was identified. Overall, the percentage of FN cases was 11.7%. The highest number of FN cases was, however, recorded for micrometastases (7.7%) compared to macrometastases (3.9%). Finally, in our study, approximately in 16.6% of all SLNBs and in 81.3% of the positive SLNs a second axillary surgery was avoided, reaching the main goal of FS.
As a result of the publication of findings of some clinical trials, in recent years there has been a progressive decline in the use of intraoperative evaluation in LS.
The results of the IBCSG 23-01 trial after a median follow-up of 9.7 years, corroborate those obtained at 5 years, showing no significant difference in terms of disease-free survival and overall survival among patients with SLN micrometastases subjected to ALND and those not subjected to ALND. Moreover, the proportion of patients with axillary lymph node failure in the no axillary dissection group was acceptably low (15, 16). These findings support the current practice of not performing an ALND in breast cancer patients with SLN micrometastases. Following this recommendation, since 2010, at our institution, ALND has been omitted in early breast cancer patients that met the IBCSG 23-10 criteria and no axillary recurrences were found during a median follow up of 65.7±8.69 months. Furthermore, a single axillary macrometastatic lymph node was found only in one patient who underwent ALND before 2010, demonstrating an extremely low risk of undertreatment in these patients (27).
With regard to patients with SLN macrometastases, two trials showed that ALND could be safety omitted in certain patients with 1 to 2 positive SLNs. The AMAROS trial showed that for patients with T1-2 primary breast cancer and no palpable lymphadenopathy, axillary radiotherapy provides excellent and comparable axillary control to ALND in patients with a positive SLN. Furthermore, axillary radiotherapy results in significantly lower morbidity (28).
The results of ACOSOG Z0011 trial showed that among women with T1-T2 invasive primary breast cancer, non-palpable axillary adenopathy, and 1 or 2 metastatic SLNs, 10-year overall survival of patients treated with SLN dissection alone was non inferior to the overall survival of those treated with ALND after a median follow-up of 9.3 years. These findings, consistent with those previously published in 2011 with a median follow-up of 6.3 years, do not support routine use of ALND in this patient population (13, 14).
These trials, and particularly the ACOSOG Z0011 trial, have substantially changed the surgical practice, leading to a progressive decline in the use of FS diagnosis for axillary SLNs. A survey of 376 surgeons in the USA found that more than 50% of interviewees do not recommend ALND in patients with 1 to 2 positive SLNs (29). Moreover, an analysis of 6,671 patients treated in 34 Breast Units certified by EUSOMA (European Society of Breast Cancer Specialists), confirmed a halving of ALND in the period between 2005 and 2016 (30). Other authors (31, 32) reported a decline in intraoperative evaluation of SLN from 69% to 26% and from 92% to 45% in the pre-Z0011 and post-Z0011. More recently, Bishop et al. (33) reported an even greater drop in FS assessment for axillary SLNs from 69% to 2% of the cases.
In our experience, the intraoperative FS avoided a delayed ALND in 16.6% of the patients who underwent SLNB. This percentage would have dropped drastically to 7.7% of the patients, if both the criteria of the IBCSG 23-01 and ACOSOG Z0011 trials were applied. However, in about a quarter of patients with 1-2 positive SLNs, three or more axillary involved nodes in the final histology after ALND were found, suggesting that omitting ALND in these patients could have been an undertreatment.
Nevertheless, if avoiding ALND in patients with SLN micrometastases is by now strongly recommended for the treatment of early breast cancer, the indications regarding patients who meet the criteria of the ACOSOG Z0011 trial are still discordant. Several criticisms were raised about the trial, the most important of which were that only 40% of the patients were enrolled compared to the initial study design and about 80% of the patients were at low risk for recurrence. Despite the fact that the NCCN (National Comprehensive Cancer Network) guidelines have incorporated the recommendation to omit ALND in patients with 1-2 macrometastatic SLNs, the NICE (National Institute for Health and Care Excellence) guidelines and the AIOM (Italian Association of Medical Oncology) guidelines suggest offering these patients the ALND once again and discussing the risks and benefits of this approach. For this reason, in our surgical practice we continue to perform ALND in all patients in whom macrometastases are found in SLNs.
Conclusion
It is evident that the approach to the axilla in breast cancer patients is still evolving and the need for conclusive confirmations of the ACOSOG Z0011 trial that will overcome its limitations is highlighted by the fact that 6 randomized studies are in progress in Europe (SINODAR ONE; Italy – POSNOC; UK – INSEMA; Germany and Austria – SERC; Francia – BOOG 2013-07; Holland – SENOMAC; Sweden). In the meantime, we believe that FS continues to be very useful in the intraoperative assessment of the SLN. In fact, compared to some negligible limits, it offers a high sensitivity and diagnostic accuracy and allows to avoid a second axillary surgery in a high percentage of patients with positive axillary lymph nodes.
Footnotes
Authors' Contributions
CC: Study conception and design, acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision of manuscript; GGr: Study conception and design, acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision of manuscript; DC: Acquisition of data, drafting of manuscript, critical revision of manuscript; GGa: Acquisition of data, analysis and interpretation of data, drafting of manuscript; ML: Study conception and design, analysis and interpretation of data, critical revision of manuscript; MRV: Study conception and design, analysis and interpretation of data, critical revision of manuscript; SV: Study conception and design, acquisition of data, analysis and interpretation of data, drafting of manuscript, critical revision of manuscript.
Conflicts of Interest
The Authors declare that they have no competing interests regarding this study.
- Received January 14, 2020.
- Revision received February 2, 2020.
- Accepted February 4, 2020.
- Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved
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