Is internal mammary nodes irradiation as a part of breast cancer postoperative radiotherapy necessary?

Breast cancer is the most common cancer among Chinese women for several years. It is also the main cause of cancer death for females (1,2). For breast cancer patients who had undergone breast-conserving surgery or a part of patients received modified radical mastectomy, radiotherapy plays a key role in the multidisciplinary treatment (3-5). However, it remains a controversy whether it is necessary to carry out internal mammary nodes (IMN) irradiation (IMNI) (6,7). In patients with breast cancer, the drainage areas of the IMN and the axillary lymph nodes have been regarded as the first nodal stations for lymphatic node drainage; however, the treatment for IMN drainage area remains controversial. Some randomized controlled trials (RCTs) have demonstrated that the extended resection of IMN did not improve the overall survival (OS) (8). Some earlier retrospective analyses also showed that the recurrence in IMN after surgery or systemic chemotherapy was rare and typically did not exceed 3% (9). For radiotherapy, the interests and controversies on IMNI are based on the findings of several recent clinical trials on radiotherapy for breast cancer (10-12); like some previous clinical trials, these trials emphasized the importance of controlling local breast cancer recurrence for long-term survival (13-16)