Lumpectomy Combined with Adjuvant Radiotherapy Could Be a Treatment Option for Primary Squamous Cell Carcinoma of the Breast

BACKGROUND: To investigate the outcomes of primary squamous cell carcinoma (PSCC) of the breast undergoing radical surgery with or without adjuvant radiotherapy (RT). MATERIALS AND METHODS: A population cohort with histologically diagnosed PSCC of the breast was identified from the SEER database. The Kaplan–Meier method and Cox-regression proportional hazards model was used to assess the impact of surgical types with or without adjuvant RT on the cause-specific survival (CSS) and overall survival (OS). A retrospective analysis of PSCC between Jan 2010 and Dec 2018 from our institute was performed. RESULTS: A total of 515 patients with PSCC of the breast were included, 254 patients treated with mastectomy (MAST) alone, 78 with MAST + RT, 87 with lumpectomy (LUMP) alone, and 96 with LUMP + RT. The median follow-up time was 118 months (range: 0–379 months). In the multivariate Cox analyses, LUMP + adjuvant RT was an independent prognostic factor for CSS (p = 0.028) and OS (p = 0.048). Patients treated with LUMP + RT had better survival rates than patients who underwent lumpectomy (CSS, p = 0.034; OS, p = 0.0004), MAST alone (CSS, p = 0.0001; OS, p < 0.0001), and MAST + RT (CSS, p = 0.0001; OS, p = 0.0078), while postmastectomy RT did not significantly improve OS (p = 0.062) and CSS (p = 0.67) when compared to MAST alone. In addition, a total of 28 patients with PSCC of the breast were identified from our institute. All of these patients presented with estrogen receptor-negative type, and three of them had HER-2-positive PSCC; the median tumor size was 3 cm (range: 0.5–15 cm). Eight patients were treated with LUMP + adjuvant RT, thirteen with MAST, and seven with MAST + RT. Until the last follow-up of Sep 2021, 26 patients with PSCC were still alive and free of breast cancer, excepting that one patient treated with MAST and one patient with MAST + RT died from breast cancer. CONCLUSION: PSCC of the breast after radical surgery has a poor prognosis. Adjuvant RT after LUMP significantly improves survival of patients with PSCC of the breast. Further studies are still needed to investigate the role of adjuvant RT in PSCC of the breast after mastectomy.