# Ultrahypofractionation in postoperative radiotherapy for breast cancer: A single‐institution retrospective cohort series

## TL;DR

A study shows that a short, intense radiotherapy schedule for breast cancer is safe and effective, with low short-term side effects and benefits for patients who are frail or live far from treatment centers.

## Contribution

The study provides real-world evidence supporting the feasibility and safety of an ultra-hypofractionated radiotherapy regimen for breast cancer patients.

## Key findings

- An ultra-hypofractionated regimen of 26 Gy in five fractions showed minimal early toxicity, primarily grade I radiodermatitis.
- Only one patient experienced local relapse during a median follow-up of 15 months.
- The regimen is particularly beneficial for frail patients or those living far from hospitals due to its short treatment duration.

## Abstract

The ‘FAST‐forward’, study published in April 2020, demonstrated the effectiveness of an extremely hypofractionated radiotherapy schedule, delivering the total radiation dose in five sessions over the course of 1 week. We share our department's experience regarding patients treated with this regimen in real‐world clinical settings, detailing outcomes related to short‐term toxicity and efficacy.

A descriptive observational study was conducted on 160 patients diagnosed with breast cancer. Between July 2020 and December 2021, patients underwent conservative surgery followed by a regimen of 26 Gy administered in five daily fractions.

The median age was 64 years (range: 43–83), with 82 patients (51.3%) treated for left‐sided breast cancer, 77 patients (48.1%) for right‐sided breast cancer, and 1 instance (0.6%) of bilateral breast cancer. Of these, 66 patients had pT1c (41.3%), 70.6% were infiltrative ductal carcinomas, and 11.3% were ductal carcinoma in situ. Most tumours exhibited intermediate grade (41.9%), were hormone receptor positive (81.3%), had low Ki‐67 (Ki‐67 < 20%; 51.9%) and were Her 2 negative (85%). The majority of surgical margins were negative (99.4%). Among the patients, 72.5% received hormonotherapy, and 23.8% received chemotherapy. Additionally, 26 patients (16.3%) received an additional tumour boost following whole breast irradiation (WHBI) of 10 Gy administered in five sessions of 2 Gy over a week. The median planning target volume (PTV) was 899 cm3 (range: 110–2509 cm3). Early toxicity was primarily grade I radiodermatitis, affecting 117 patients (73.1%). During a median follow‐up of 15 months (range: 3.9–28.77), only one patient experienced a local relapse, which required mastectomy.

The implementation of this highly hypofractionated regimen in early‐stage breast cancer appears feasible and demonstrates minimal early toxicity. However, a more extended follow‐up duration would be required to evaluate long‐term toxicity and efficacy accurately.

An ultra‐hypofractionated radiotherapy schedule is safe and effective after breast‐conserving surgery. 26 Gy in five fractions shows low acute toxicity. Most patients had grade one radiodermitis (73.1%). This scheme has important clinical benefits for patients who are frail o live far from the hospital in addition to economic advantages.