Changes in Fractionation Schedules for Breast Cancer Treatment during the COVID-19 Pandemic

PURPOSE/OBJECTIVE(S): In 2020, 5-year results of the FAST-Forward trial and 10-year results for both the FAST trial and APBI-IMRT-Florence trials using ultrahypofractionated radiation (UHFR) were all published, each detailing equivalent outcomes for partial and whole breast UHFR schedules compared to more conventional fractionation regimes in early-stage breast cancer. Due to concerns over viral exposure, these treatment regimens were adopted in an effort to minimize patient exposure while achieving equivalent oncologic control. The purpose of this study was to compare the use of UHFR schedules for breast cancer patients before COVID-19, at the height of the pandemic and after widespread vaccination and analyze factors predictive of use. MATERIALS/METHODS: Between October 2019 and February 2022, 733 patients with stage 0 or I breast cancer were offered radiation at our institution following breast conserving surgery. 43 patients were excluded (35 declined radiation and 8 received partial breast re-irradiation). We analyzed target volume (whole vs partial breast) and fractionation schemes (1 week vs 3 or more weeks) for 3 time periods of interest: pre-COVID-19 (October 2019-March 2020), height of COVID-19 (March 2020-March 2021) and post-COVID-19 vaccine (March 2021-February 2022). Fisher's exact test was used to compare frequencies of treatment parameters across groups and time periods. Logistic regression was used to determine factors associated with UHFR use. R (v4.1.2) was used for analysis. RESULTS: The use of UHFR increased during the post-vaccine period as compared to pre-Covid-19 and the pre-vaccine time periods (p<0.001), with 4.6%, 9.2% and 23%, receiving UHFR respectively. On univariate analysis in the pre-vaccine time period, patients with grade 2 and 3 cancers were less likely to get UHFR (p = 0.003 and p = 0.005, respectively). Receiving radiation from an academic attending was associated with higher use of UHFR (p = 0.0004). On multivariate (MVA) patients with grade 2 and 3 disease remained less likely to get UHFR (p 0.001 and 0.004). Treatment by an academic attending remained a significant factor for use of UHFR (p=0.0003). In the post-vaccine time period, on univariate analysis, negative ER status and grade 3 tumors were associated with less use of UHFR (p = 0.04 and p = 0.0001, respectively). On MVA, only grade 3 was associated with less UHFR use (p = 0.0002). CONCLUSION: During COVID there was a significant increase in the use of UHFR regimens for treatment of early-stage breast cancer patients at our institution that persisted and increased after the introduction of the vaccine despite return to pre-COVID patient volumes. Uptake of these new regimens was initially higher among academic radiation oncologists, however with education of community physicians and implementation of treatment planning scorecards, widespread adoption was seen.