Treatment Outcome and Skin Complications in Tumor Bed Boost Radiotherapy Using Photons or Electrons in Breast Cancer Patients after Breast-Conserving Surgery

Background and Objective: In patients with breast cancer, the administration of an additional dose of radiotherapy to the tumor bed after breast treatment is associated with a decrease in local recurrence. Electron source is mainly used due to proper dose distribution and lack of skin irradiation. Nevertheless, access to electrons is not possible in all medical centers. Therefore, continuing treatment using smaller photon fields may be a reasonable option. The aim of this study is to investigate and compare the outcome of treatment and skin complications in tumor bed boost radiotherapy using photons or electrons in breast cancer patients after breast-conserving surgery. Methods: In this retrospective cohort, 280 patients with non-metastatic breast cancer who underwent breast-conserving surgery and adjuvant radiotherapy were included in the study. After whole breast radiotherapy with conventional regimen (50 Gy in 25 sessions), the patients underwent tumor bed boost with electrons or photons (with a dose of 10 Gy in 5 sessions) (electron: 145 people, photon: 135 people). Survival values, cosmetic results (Harvard Harris criteria) and skin toxicity (5th edition of General Toxicity Criteria and Adverse Effects) were compared between the two groups during the follow-up of patients. Findings: Recurrence-free survival in the same breast was not significantly different in two groups (recurrence-free survival in photon boost 95% (with a 95% confidence interval between 9% and 97%) and electron boost 93% (with a 95% confidence interval between 79% and 97) (p=0.69). There was no difference between radiotherapy-induced dermatitis and subcutaneous toxicity at the end of the treatment between the two treatment groups. However, one month after the end of the treatment, the cases of severe radiotherapy-induced dermatitis were higher in the photon treatment group (88% vs. 65.5%, p=0.007). However, the subcutaneous toxicity 2 months after the end of treatment was significantly higher in the electron boost group (0% vs. 7.5%, p