Overall survival worsened as the number of interrupted treatment days increased.

The impact of treatment interruptions during courses of adjuvant radiation therapy for breast cancer has not been investigated. To address this issue, investigators conducted a study of 35,845 triple-negative breast cancer (TNBC) patients in the National Cancer Database who received external beam radiation and had overall survival (OS) of at least 12 months. Among these patients, 76% had grade III to IV disease and 68% had N0 cancer.

Multivariable Cox proportional hazard models were used to determine the association between interrupted treatment days and OS. The number of interrupted treatment days was defined as the total number of days from the start to the end of treatment minus the number of expected days of treatment. OS was defined as the time between the date of diagnosis and the date of death.

As the number of interrupted treatment days increased, OS progressively worsened. Compared with zero to one interrupted treatment days, hazard ratios for poorer OS were 1.069 for two to five interrupted treatment days, 1.239 for six to 10 interrupted treatment days and 1.265 for 11 to 15 interrupted treatment days. Other factors significantly associated with poorer OS were Black versus white race (HR, 1.278), other nonwhite versus white race (HR, 1.337), grade III to IV versus grade I disease (HR, 1.743) and stage N1 to N3 versus N0 disease (HR, 2.534 to 4.992). 

Comment: These results suggest that it may be better for patients to try to ‘push through’ radiation-related toxicities rather than interrupt therapy. To that end, the investigators suggest exploring prophylactic measures and alternative therapies to minimize acute toxicities. Avoiding interruptions should especially be encouraged in patients with aggressive features, such as high-grade disease and node positivity, that negatively affect outcome. The results also raise the issue of whether social determinants of health (employment issues, family resources and support, transportation, etc.), especially in certain populations, amplify the effect of treatment interruptions.

William J. Gradishar, MD, Professor of Medicine and Director of Breast Medical Oncology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, USA.

Chow R, et al. Effect of treatment interruptions on overall survival in patients with triple-negative breast cancer. J Natl Cancer Inst 2023; 115: 1029-1035.

This summary is taken from the following Journal Watch titles: Oncology and Hematology.