Postoperative Radiotherapy Using VMAT for RNI Including IMN in Breast Cancer: Report of Short-term Follow-up.

Background/aim: The application of volumetric-modulated arc therapy (VMAT) in postoperative radiotherapy for breast cancer has recently garnered considerable interest, especially when regional lymph node irradiation (RNI), is extended to include the internal mammary node (IMN) region, along with whole-breast or chest wall irradiation. This study aimed to assess both acute and late toxicities, as well as breast cancer outcomes, during the observation period.

Patients And Methods: This retrospective study aimed to assess the safety and feasibility of VMAT in postoperative radiotherapy, including the IMN region, for patients with breast cancer at our hospital. We included 33 eligible patients who received postoperative VMAT radiotherapy, including the IMN region, between November 2018 and July 2021.

Results: The primary indications for implementing VMAT were the presence of IMN metastases before primary systemic therapy or more than four axillary lymph node metastases. The median prescribed dose for the chest wall or conserved breast and regional lymph nodes was 50 Gy in 25 fractions. In 16 cases, a simultaneous boost (median, 10 Gy) was administered to residual lymph node metastases. VMAT facilitated a reduction in the mid- or high-dose range to organs at risk, exemplified by V and V of the ipsilateral lung, which were 24.10% and 6.84%, respectively, while ensuring adequate target dose irradiation, V=95.23%. No serious adverse events, including symptomatic radiation pneumonitis, occurred during the 15-month median observation period.

Conclusion: Our findings demonstrate the safety and effectiveness of postoperative radiotherapy for breast cancer, including the IMN region, when using VMAT.