KEY POINTS
- The FASTF-PG01 observational study enrolled 2,036 patients from 28 Italian radiotherapy centres between 2020 and 2025. All had early-stage invasive breast cancer or ductal carcinoma in situ treated with breast-conserving surgery; regional nodal irradiation was excluded.
- All patients received whole-breast irradiation of 26 Gy in five consecutive 5.2 Gy fractions. A tumour-bed boost was delivered in 20.4%: 7.6 Gy in two sequential fractions in 233 patients or a simultaneous integrated boost to 30 Gy in five fractions in 184.
- Acute erythema occurred in 37.1%, but 90.2% of these events were grade 1 and only 8 patients, or 0.4% of the full cohort, developed grade 3 erythema. Breast oedema occurred in 7.1%, with one grade 3 event, and breast pain in 10.1%.
- Every patient completed the prescribed radiotherapy without interruption. Treatment technique - three-dimensional conformal radiotherapy, intensity-modulated radiotherapy or volumetric modulated arc therapy - was not significantly associated with acute or short-term late toxicity.
- Skin hyperpigmentation declined from 12.2% at six months to 4.0% at 24 months, and almost all events were grade 1. Breast induration was 10.2% at six months and 13.2% at 24 months, with only two grade 2 events and no grade 3 events among the 326 patients assessed at two years.
- Acute toxicity was independently associated with active smoking (odds ratio 1.40), boost administration (1.35) and increasing breast planning target volume. Increasing age was associated with lower acute-toxicity risk (odds ratio 0.972 per year).
- Active smoking was associated with late toxicity at six months (odds ratio 2.41), while larger boost volume predicted toxicity at six and 12 months. Sequential and simultaneous integrated boost delivery produced similar toxicity rates.
CLINICAL TAKEAWAY
These data support the practical short-term tolerability of 26 Gy in five fractions across diverse centres and techniques, including selected patients receiving a boost. They do not add strong evidence on efficacy or mature safety: median follow-up was only 12 months, just 326 patients were assessed at two years, and cosmetic and quality-of-life outcomes were not included in this interim analysis.
SOURCE
International Journal of Radiation Oncology, Biology, Physics