Locoregional control and toxicity following high-dose hypofractionated and accelerated palliative radiotherapy regimens in breast cancer

Abstract

Aims: For patients with locally advanced primary/recurrent breast cancer, radiotherapy is an effective treatment for locoregional control. 36 Gy in 6 Gy once-weekly fractions is a commonly used schedule, but there are no data comparing local control and toxicity between 36 Gy delivered once-weekly versus accelerated schedules of multiple 6 Gy fractions per week. This retrospective study compared local control rates and acute and late toxicity in patients undergoing 30-36 Gy in 6 Gy fractions over 6 weeks versus more accelerated schedules over 2-3 weeks for an unresected breast cancer.

Materials and methods: Patients who received 30-36 Gy in 6 Gy fractions to an unresected breast cancer ± involved lymph nodes between December 2011 and August 2020 were identified. Patients were grouped into once-weekly versus accelerated fractionation schedules. Response rates, local control and toxicity data were analysed.

Results: In total, 109 patients were identified. The median follow-up duration was 46 months. Forty-seven patients (43%) received once-weekly fractions and 62 patients (57%) received accelerated fractionation schedules. There were no significant differences in baseline tumour characteristics between the groups. Eighty-seven per cent of patients had an objective (complete or partial) response (81% in the once-weekly group; 91% in the accelerated group). The median time to local progression was 23.5 months overall (95% confidence interval 17.8-29.2); 23.5 months (95% confidence interval 18.8-28.1) in the once-weekly group and 19.0 months (95% confidence interval 7.0-31.1) in the accelerated group (P = 0.99). Acute toxicity of any grade occurred in 75% of patients (76% in the once-weekly group; 74% in the accelerated group) and grade 3 toxicity occurred in 7% of patients (7% in the once-weekly group; 8% in the accelerated group). There were no associations between the groups and acute or late toxicity grade (P = 0.78 and P = 0.26, respectively), although one grade 4 late toxicity (skin radionecrosis) occurred in a patient who received five fractions a week and therefore this regimen is not recommended. Study limitations included a lack of statistical power analysis, the necessary grouping of all accelerated patients for analysis and a high rate of censored data.

Conclusion: There were no apparent differences in response rate, time to local progression or toxicity between patients who received 30-36 Gy in 6 Gy fractions once-weekly compared with twice-weekly as palliative treatment for locally advanced breast cancer. This regimen appears to be a safe alternative and may be preferred by patients.

Keywords: Breast cancer; Hypofractionation; Palliative radiotherapy.