Use of hypofractionated radiation therapy for breast cancer in the post-mastectomy settings in Victoria.

Abstract

Purpose: There is emerging evidence supporting the use of hypofractionated radiation therapy (HFRT) for breast cancer (BC) following mastectomy. We aim to evaluate the use of HFRT in the post-mastectomy settings, and identify factors associated with it in Victoria, Australia Methods and Materials: We used the population-based Victorian Radiotherapy Minimum Dataset (VRMDS) to identify women with BC who received RT to the chest wall +/- nodal irradiation following mastectomy between 2012 to 2017. We defined HFRT as <25 fractions of RT. We used the Cochrane Armitage test to evaluate the changing pattern of HFRT use, looking at differences in patient, treatment, and provider factors associated with HFRT using Pearson's chisquared test for categorical variables and t-test for continuous variables. Finally, we used multivariable logistic regression to identify factors associated with HFRT use. Result(s): Of 2021 women, 241 women (12%) received HFRT, and this increased from 8% in 2012 to 18% in 2017 (P-trend < 0.001). Older women were more likely to receive HFRT (26% of women aged >70 years vs. 7% of women aged <50 years; p < 0.001). Women who did not have nodal irradiation were more likely to have HFRT compared to those who had nodal irradiation (18% vs 9% respectively; p < 0.001). There were no differences in HFRT use by socioeconomic status, area of residence, treatment institution type and location. In multivariate analyses, the progressive increase in HFRT use was observed after adjusting for other factors-women treated in 2017 were 3.9 times more likely to receive HFRT than those treated in 2012 (95% CI = 2.0-7.5; p < 0.001). Age at RT, nodal irradiation and area of residence were independently associated with HFRT use in multivariate analyses. Women aged >70 years were 4.8 times more likely to be treated with HFRT compared to those aged <50 years (95% CI = 3.3-7.1; p < 0.001), and those who had nodal irradiation were 66% less likely to have HFRT (95% CI = 54-75%; p < 0.001). Women from regional areas were 41% less likely to receive HFRT compared to metropolitan areas (95% CI = 16-58%; p = 0.003). Conclusion(s): While there are multiple Australian studies evaluating the HFRT use for BC post-breast conserving surgery, this is to the best of our knowledge the first Australian study to evaluate HFRT use in post-mastectomy settings. HFRT was increasingly used in the post-mastectomy settings in Victoria during the mid 2010s, though variation remains depending on patient demographics and treatment related factors.