The evolutionary development of adjuvant radiotherapy in breast cancer. Part I. The role of regional lymph nodes (n+, n-)

It is well known that postoperative radiotherapy (PORT) for breast cancer, in particular after radical mastectomy, has long been used to increase local-regional control, compared with local surgical intervention in a certain group of oncological patients. At the same time, in recent decades, a fairly clear advantage in the survival of breast cancer patients with a higher risk of progression of the underlying disease has also been revealed, based mainly on the characteristics of the primary tumor rather than the presence of only metastatic lesions of regional lymph nodes after PORT implementation, compared to those who have not undergone it. During this time, the landscape of special treatment of breast cancer has changed towards less invasive operations and at the same time, both more effective schemes of antitumor systemic chemotherapy, and the implementation of more modern methods of high-tech radiotherapy, which, in particular, contribute to a significantreduction in the risk of severe side effects, compared with previously used imperfect in technologically, the historical methods of postoperative irradiation. This review will focus on the significance of PORT in terms of possible improvements in radiation efficacy after radical mastectomy in patients with both metastatic regional lymph nodes (N+) and unaffected lymph nodes (N-), but with signs of high risk of underlying disease progression due to the existing prognostically unfavorable significant characteristics of the primary tumor. The future directions of the PORT development and current clinical trials studying the advantages (or disadvantages) of additional radiation and the possible rejection of postoperative radiation altogether will also be discussed. At the same time, some questions as to which patients are definitely eligible for PORT and which patients may not, if there is significant prognostic evidence that the likelihood of recurrence of the underlying disease after radical mastectomy is significantly low, remain without a definitive answer. However, it seems certain that any patient with a large tumor or metastatic involvement of regional lymph nodes or other signs of high risk of underlying disease progression should be discussed collectively to evaluate this clinical observation individually and develop the most appropriate specific treatment tactics.