Clinical significance of supraclavicular lymph node (SCLN) dissection for patients with breast cancer with ipsilateral SCLN metastasis.

e13110 Background: Breast cancer with ipsilateral supraclavicular lymph node (SCLN) metastasis is defined as Ⅲc stage according to the 8th AJCC system. It is still pending whether to exert SCLN dissection except for regional radiotherapy to such patients. Methods: Breast cancer patients with ipsilateral SCLN metastasis from 2019.02 to 2024.01 in multiple centers in Hubei China, were enrolled. Patients received either SCLN radiotherapy alone or combined with SCLN dissection. All patients received standard therapy recommended by the NCCN guidelines. The primary endpoint was 5-year disease free survival (DFS), and secondary endpoints were complication rates, overall survival (OS), and quality of life scores. Results: As of 2024.01, a total of 181 patients with a median age of 51 years (28-78 years) were enrolled. 177 patients received neoadjuvant therapy and 4 patients underwent surgery followed by adjuvant therapy. The molecular subtyping composition was Luminal (HR+, HER2-, 38%), TNBC (triple negative breast cancer, HR-, HER2-, 23%), HER2+ (HR-, HER2+, 20%) and TPBC (triple positive breast cancer, HR+, HER2+, 19%). Of the 177 neoadjuvant treated-patients, 71.2% did not achieve pathological complete response (pCR). The percentage of molecular subtyping in non-pCR neoadjuvant patients was Luminal 45%, TNBC 26%, HER2+ 15%, and TPBC 14%, while those who got pCR were HER2+ 35%, TPBC 31%, Luminal 18%, and TNBC 16%. A total of 27 recurrent and/or metastatic events occurred, with 14.5% (8/55) in the experimental group (with SCLN dissection) and 15.1% (19/126) in the control group; while Luminal accounted for 13.4% (9/67), TPBC 13.9% (5/36), HER2+ 16.2% (6/37) and TNBC 17.1% (7/41). Using questionnaires, we found that both groups resulted in comparable complication rates, and quality of life scores were better in the group that did not undergo SCLN dissection. Conclusions: According to the preliminary results, we found several interesting phenomena. First, patients with SCLN metastasis had a higher percentage of HER2 overexpression, including HER2+ and TPBC, up to 39%. Second, receiving neoadjuvant therapy, TPBC and HER2+ subtypes were more likely to achieve pCR, possibly due to the use of dual-targeted agents. Third, even the median follow-up time has not yet been reached, preliminary data suggested that the recurrent and metastatic rates were comparable in both groups and four subtypes. These data seem to suggest that in patients with ipsilateral SCLN metastasis, SCLN dissection is not mandatory with effective systematic therapy and radiotherapy. In addition, for Luminal subtype, adjuvant therapy should not be taken lightly, while for HER2 overexpressing and TNBC subtypes, the necessity of intensive therapy is no longer purposely highlighted. Of course, we also look forward to the final statistical analysis of the differences in the primary endpoints to bring us a better answer. Clinical trial information: NCT03716245 .