The trial enrolled 160 adult patients with early-stage squamous cell carcinoma of the anus, most of whom were female with tumors ≤ 4 cm. Patients were randomly assigned to receive either the standard radiation dose of 50.4 Gy or a lower dose of 41.4 Gy. Both groups received concurrent mitomycin and capecitabine.
At 6 months posttreatment, 92% of the patients in the reduced-dose group achieved a complete clinical response compared with 87% of those in the standard-dose group.
The patients receiving the lower dose also experienced fewer side effects. Grade 3 or worse toxicities such as radiation dermatitis or diarrhea occurred in 35% of the patients in the reduced-dose group and 46% of those in the standard-dose group. Serious adverse events, including infections or cardiac events, occurred in 10% and 15% of patients, respectively.
“Early results suggest [reduced-dose intensity-modulated radiotherapy] is well tolerated with oncologic outcomes maintained,” said lead study author Alexandra Gilbert, FRCR, of the Leeds Institute of Medical Research at St James’s at the University of Leeds, and colleagues.
Treatment compliance was better in the reduced-dose group. Interruptions in radiotherapy of 3 or more days occurred in 15% of the patients compared with 26% in the standard group. Chemotherapy modifications were also less frequent (37% vs 49%), mostly because of toxicity.
The patients also reported their own symptoms and quality of life. While many experienced declines in energy, bowel function, and sexual function during treatment, most symptoms improved by 6 weeks and returned to baseline by 6 months. Male and female patients in the reduced-dose group reported greater recovery in sexual function compared with those in the standard group.
Among the tumors evaluated, 93% were positive for p16, a marker commonly associated with human papillomavirus–related anal cancer. All nine p16-negative patients with available data also achieved complete response at 6 months.
The participants generally had good baseline health, with an ECOG performance status of 0 to 1. These findings suggested that less intensive treatment may be a feasible option among patients with small, localized disease—particularly older adult patients—without compromising short-term cancer control.
The study’s primary outcome—locoregional cancer recurrence after 3 years—is still being assessed. However, these early results suggested that reduced-dose treatment may offer a safer, effective alternative in select patients.
The authors reported no competing interests.
Source: The Lancet Oncology
