Local control and toxicity after hypofractionated accelerated palliative RT in breast cancer
Katharine Webb,
United Kingdom
PD-0748
Abstract
Local control and toxicity after hypofractionated accelerated palliative RT in breast cancer
Authors: Katharine Webb1, Lone Gothard2, Kabir Mohammed3, Anna Kirby1,2, Imogen Locke1, Navita Somaiah1,2
1The Royal Marsden NHS Foundation Trust, Breast Unit, Sutton, United Kingdom; 2The Institute of Cancer Research, Division of Radiotherapy and Imaging, London, United Kingdom; 3The Royal Marsden NHS Foundation Trust, Research and Development Department, Sutton, United Kingdom
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Purpose or Objective
For patients with locally advanced primary or recurrent breast cancer, radiotherapy (RT) is an effective treatment for loco-regional control. Hypofractionated RT is radiobiologically justified given the low α/β ratio of breast tumours and is convenient for patients due to fewer visits. 30-36Gy in 6Gy once-weekly fractions over 5-6 weeks is a common high-dose palliative regimen in breast cancer. A reduction in overall treatment time may lead to improved loco-regional control by limiting tumour cell repopulation, although it may increase acute toxicity. However, there are no data comparing local control and toxicity between once-weekly fractions and accelerated schedules of twice or more weekly fractions.
Material and Methods
In this retrospective, single institution study, all patients receiving 30-36Gy in 6Gy fractions to an unresected breast cancer +/- involved lymph nodes between December 2011 and August 2020 were identified (nodal irradiation did not exceed 30Gy in 5 fractions to respect brachial plexus tolerance). Patients were grouped into once-weekly versus accelerated fractionation schedules. Response rates, local control and toxicity data were analysed.
Results
109 patients were identified. Median follow-up duration was 46 months. 47 patients (43%) received once-weekly fractions and 62 patients (57%) received accelerated fractionation schedules (26, 24, and 12 patients received 2, 3 and 5 fractions a week, respectively). The majority of patients in both groups had T3/T4 disease (81% in once-weekly group; 88% in accelerated group) and had progressed on systemic treatments. 87% of patients had an objective (complete or partial) response to RT (81% in once-weekly group; 91% in accelerated group). Median time to local progression was 23.5 months overall (95% CI 17.8-29.2); 23.5 months (95% CI 18.8-28.1) in once-weekly group and 19.0 months (95% CI 7.0-31.1) in accelerated group (p=0.99). Acute toxicity of any grade occurred in 75% of patients (76% in once-weekly group; 74% in accelerated group), and grade 3 toxicity occurred in 7% of patients (7% in once-weekly group; 8% in accelerated group). There was no association between the groups and acute toxicity grade (p=0.779). Although late toxicity was only documented for 48 patients, there was no apparent association between the groups and late toxicity grade (p=0.263), although one grade 4 late toxicity (skin radionecrosis) occurred in a patient who received 5 fractions on consecutive weekdays.
Conclusion
There was no apparent difference in response rate, time to local progression or acute toxicity between patients who received once-weekly fractions and accelerated fractionation schedules. The accelerated regimens appear to be a safe alternative to the once-weekly regimen, may be preferred by patients and may also minimise interruptions to concurrent systemic therapy.