Phase III Trial Explores Internal Mammary Node Irradiation in Node-Positive Breast Cancer
Posted: Wednesday, December 1, 2021
Yong Bae Kim, MD, of Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, Korea, and colleagues examined whether the use of internal mammary area irradiation in regional nodal irradiation enhanced outcomes in patients with node-positive breast cancer. Presented during the 2021 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 2), their results concluded that women with medially located tumors appeared to experience significantly improved disease-free survival with this treatment compared with those who did not receive it.
This phase III trial enrolled 747 patients with node-positive breast cancer who underwent regional nodal irradiation and either breast-conserving surgery or mastectomy with axillary lymph node dissection; individuals who had adjuvant treatment or distant metastasis were excluded. Stratified by lymph node metastasis, 362 participants were randomly assigned to receive internal mammary area irradiation, and 373 received no internal mammary area irradiation.
The median follow-up was 8.4 years, and nearly all patients received taxane-based adjuvant systemic treatment. Breast cancer–related events affected 127 participants, and 89 died. The 7-year disease-free survival rates for those who did not receive internal mammary area irradiation as well as those who did were 81.9% and 85.3%, respectively (hazard ratio [HR] = 0.80; P = .22).
Among patients with mediocentrally located tumors, there was a significant improvement in disease-free survival in the treatment (91.8%) and non-treatment (81.6%) arms (HR = 0.42; P = .01). Additionally, there was an observed significant decrease in 7-year breast cancer mortality rate among these patients, with 4.9% of individuals who did and 10.2% of those who did not undergo internal mammary area irradiation dying of breast cancer. Furthermore, there was no apparent difference in adverse events between the treatment arms.
Disclosure: The study authors reported no conflicts of interest.
