Hypofractionated SIB reduced acute dermatitis in the randomized HYPOSIB trial

KEY POINTS

• The international randomized HYPOSIB trial (NCT02474641) enrolled 2,310 patients across 94 centres after breast-conserving surgery. The acute-toxicity analysis included 2,264 treated patients: 1,122 receiving HYPOSIB and 1,142 standard radiotherapy.
• HYPOSIB delivered 40 Gy in 16 fractions to the whole breast with a simultaneous integrated boost to 48 Gy in 16 fractions. Standard treatment could use 42.5 Gy in 16 fractions plus sequential boost, 50.4 Gy in 28 fractions plus sequential boost, or 50.4 Gy in 28 fractions with a simultaneous boost to 58.8–63 Gy.
• Worst grade 2 radiation dermatitis occurred in 25.3% with HYPOSIB versus 38.6% with standard treatment, an absolute reduction of 13.3 percentage points. Grade 3 dermatitis occurred in 2.3% versus 3.1%, respectively.
• Dermatitis developed and resolved earlier with HYPOSIB. Grade 2 toxicity peaked at 15.1% on day 36 with HYPOSIB compared with 22.7% on day 50 in the standard arm.
• Even compared specifically with moderately hypofractionated treatment using a sequential boost, grade 2 dermatitis peaked at 15.1% versus 25.3% on day 36, suggesting that the difference was not explained solely by conventional fractionation.
• Worst-grade pain, breast discomfort, and nausea differed by less than approximately 2 percentage points for grade 2–3 events between groups. Grade 3 pain was uncommon, occurring in approximately 3% overall.
• This report addresses a secondary acute-safety endpoint rather than the trial’s primary disease-free survival endpoint. Detailed late toxicity and quality-of-life analyses are still required before judging the full trade-off between the two schedules.

CLINICAL TAKEAWAY

SOURCE

International Journal of Radiation Oncology, Biology, Physics