Durable therapeutic gain despite competing mortality in long-term follow-up of a randomized hyperfractionated radiotherapy trial for locally advanced head and neck cancer.

Purpose/objectives: To examine the therapeutic ratio and mortality profile over time in a radiotherapy randomized trial in stage III-IV larynx/pharynx cancer with long-term follow-up.

Materials/methods: From 1988 to 1995, 331 cases were randomized to either hyperfractionated (HF) (58 Gy/40 fractions, twice daily) or conventional (CF) (51 Gy/20 fractions, once daily) radiotherapy. Overall survival (OS), locoregional (LRC), distant control (DC), ≥Grade 3 late toxicity (LT), and relative mortality risk profile over time were compared between both arms.

Results: Median follow-up was 13.6 years. HF had a 10% improved OS at 5-years (40% vs 30%, p = 0.04), but the benefit diminished to 3% at 10-years (21% vs 18%). A trend towards higher LRC with HF remained (5-year: 49% vs 40%; 10-year: 49% vs 39%, p = 0.05). DC rates were unchanged (5-year: 87% vs 85%; 10-year: 87 vs 84%, p = 0.56). LT rates were similar (HF vs CF: 5-year: 9% vs 12%; 10-year: 11% vs 14%, p = 0.27). Multivariable analysis confirmed that HF reduced mortality risk by 31% [HR 0.69 (0.55-0.88), p < 0.01] and locoregional failure risk by 35% [HR 0.65 (0.48-0.89), p < 0.01]. Index cancer mortality (5-year: 46% vs 51%; 10-year: 49% vs 55%) was lower in the HF arm. Competing mortality (mostly smoking-related) was also numerically lower with HF at 5-years (14% vs 19%) but became similar at 10-years (30% vs 28%).

Conclusions: This trial confirms that HF with augmented total dose has a durable 10% effect size on LRC with comparable LT. OS benefit is evident at 5-years (10%) but relative mortality risk profile changes in longer follow-up.