Predictors of Whole Breast Radiation Therapy Completion in Early Stage Breast Cancer Following Lumpectomy.

BACKGROUND

Whole breast radiation therapy (RT) has become standard of care in early stage breast cancer treatment following lumpectomy. Predictors of RT completion have been sparsely studied, with no previous nationwide examination of the impact of fractionation regimen on completion rate.

PATIENTS AND

METHODS

The National Cancer Database identified patients with early stage breast cancer having undergone lumpectomy and RT from 2004 through 2015. Fraction size of 1.8-2.0 Gray (Gy) was defined as standard fractionation (SFRT); 2.66-2.70 Gy/fraction as hypofractionation (HFRT). RT completion was defined as receipt of at least 46 Gy for SFRT and 40 Gy for HFRT. A multivariable logistic regression model characterized RT completion predictors.

RESULTS

A total of 100,734 patients were identified where fraction size could be reliably characterized as above; more than 87% completed RT. Of these, 66.8% received SFRT, yet HFRT use significantly increased over time (5.2% increase/year; P < .0001). RT completion rates were significantly greater following HFRT (99.3%) versus SFRT (79.7%); patients receiving SFRT had higher odds of not completing RT (odds ratio, 41.5; 95% confidence interval, 36.6-47.1; P < .0001). Multivariable analysis revealed that African-American and Caucasian patients treated with SFRT versus HFRT had 22 and 43 times the odds of not completing RT, respectively (P < .0001).

CONCLUSIONS

SFRT remained the majority of RT fractionation in the studied time period, although HFRT use has increased over time. Patients residing > 10 miles from a treatment facility or of African-American race had lower odds of completing RT, as were patients treated with SFRT versus HFRT. These findings suggest compliance advantages of HFRT for patients with early stage breast cancer having undergone lumpectomy.