The Impact of Radiotherapy Delay in Breast Conservation Patients Not Receiving Chemotherapy and the Rationale for Dichotomizing the Radiation Oncology Time-Dependent Standard into Two Quality Measures.

Introduction: The Commission on Cancer/National Quality Forum breast radiotherapy quality measure establishes that for women < 70 years, adjuvant radiotherapy after breast conserving surgery (BCS) should be started < 1 year from diagnosis. This was intended to prevent accidental radiotherapy omission or delay due to a long interval between surgery and chemotherapy completion, when radiation is delivered. However, the impact on patients not receiving chemotherapy, who proceed from surgery directly to radiotherapy, remains unknown.

Patients And Methods: Patients aged 18-69, diagnosed with stage I-III breast cancer as their first and only cancer diagnosis (2004-2016), having BCS, for whom this measure would be applicable, were reviewed from the National Cancer Database.

Results: Among 308,521 patients, the median age was 57.0 years, and > 99% of all patients were compliant with the measure. The cohort of interest included 186,650 (60.5%) patients not receiving chemotherapy, with a mean age of 57.9 years. Of these, 90.5% received external beam radiotherapy (EBRT) and 9.5% brachytherapy. Among them, 24.9% started radiotherapy > 8 weeks after surgery. In a multivariable model, delay from surgery to radiotherapy increased the hazard ratios for overall survival to 9.0% (EBRT) per month and 3.0% (brachytherapy) per week.

Conclusion: While 99.9% of patients undergoing BCS without chemotherapy remain compliant with the current quality measure, 25% have delays > 8 weeks to start radiation, which is associated with impaired survival. These data suggest that the current quality measure should be dichotomized into two, with or without chemotherapy, in order to impel prompt radiotherapy initiation and maximize outcomes in all patients.