Factors associated with radiation therapy incompletion for patients with early-stage breast cancer.

Purpose: The purpose of the study was to examine factors associated with adjuvant radiation treatment (RT) incompletion for women with breast cancer within a large national cancer database.

Methods: We identified 394,334 women diagnosed with stage I-III breast cancer during 2004-2012 in the national cancer database who initiated adjuvant external beam adjuvant RT and examined the proportion of women not completing treatment. We used multivariable logistic regression to examine patient, clinical, and facility factors associated with RT incompletion for those who had breast-conserving surgery (BCS), defined as <15 fractions and <3990 centiGray [cGy] (accounting for adoption of hypofractionation), and mastectomy (PMRT, defined as <5000 cGy and <25 fractions), separately. We also examined RT incompletion after BCS using more traditional definitions of <25 fractions and <4500 cGy for diagnosis years ≤2010.

Results: Among the 319,003 women who underwent BCS and the 75,331 women who underwent mastectomy and initiated RT, 98.4 and 97.8 % completed radiation, respectively. In adjusted analyses, older age was associated with RT incompletion (odds ratio [O.R.] for age ≥80 = 2.53 for BCS-treated, 95 % confidence interval [CI] 2.19-2.92; O.R. for PMRT incompletion = 2.33, 95 % CI 1.84-2.96; both versus age <50). In addition, those with ≥2 comorbidities and lower-risk disease had higher odds of RT incompletion. After defining RT completion using more traditional definitions, 94.0 % completed treatment.

Conclusions: Reassuringly, we found a very low proportion of patients not completing RT, though we observed a higher likelihood for treatment incompletion in some sub-groups, most notably older women. Further studies should focus on reasons for treatment discontinuation in populations at risk for suboptimal treatment.