General analysis of breast cancer patients tested for BRCA mutations and evaluation of acute radiotherapy toxicity.

Objective: The objective of our study is to evaluate breast cancer patients with BRCA1 or BRCA2 gene mutations and compare them with patients without these mutations. Specifically, we aim to assess the acute side effects of radiotherapy in both groups.

Methods: Data were collected from four participating centers, comprising information from 73 patients who underwent known mutation analysis and had complete data. Patients were monitored on a weekly basis throughout their treatment for acute toxicity, which was evaluated using the Radiation Therapy Oncology Group (RTOG) acute toxicity criteria.

Results: The median age of the 73 patients included in our study was 43. Among them, 17 had BRCA1-positive mutations and 19 had BRCA2-positive mutations. Invasive ductal carcinoma was present in 67 patients, all of whom underwent surgery. Of the patients, 57 received conventional radiotherapy doses, while 16 received hypofractionated radiotherapy doses. During follow-up, metastasis occurred in three patients. In BRCA-positive patients, those under 40 years of age (p<0.001), with high nodal positivity (p=0.008), grade 2-3 (p=0.022), and lymphovascular invasion (p=0.002) were significantly more frequent compared to BRCA-negative patients (p<0.001). The median survival was 35.8 months. Grade 1 dysphagia developed in seven BRCA-negative patients and four BRCA-positive patients, with no significant difference observed between the two groups (p=0.351). There was also no statistical difference observed in the occurrence of grade 2-3 skin reactions, with 11 BRCA-negative patients and eight BRCA-positive patients experiencing these side effects.

Conclusion: Our study supports existing literature by identifying an association between the presence of BRCA mutations and young age, nodal status, grade, and lymphovascular invasion. Additionally, we found no significant difference in the occurrence of radiotherapy toxicity between BRCA-positive and BRCA-negative patients. These findings suggest that radiotherapy can be safely administered to BRCA-positive patients after breast-conserving surgery or mastectomy. Keywords for our study include breast cancer, BRCA mutation, radiotherapy, and side effects.