Hypofractionated radiation equivalent to standard radiation for breast cancer at 10-years

Researchers in Canada have found that women with breast cancer treated with hypofractionated whole-breast irradiation had similar risk for local recurrence and survival outcomes as women assigned to the standard five-week course.

These new findings update five-year results of a meta-analysis conducted by the Early Breast Cancer Trialists’ Collaborative Group.

From 1993 to 1996, 1,234 women received whole-breast irradiation following breast conserving surgery. Researchers randomly assigned 612 patients to the standard dose of 50 Gy administered in 25 fractions over five weeks. Another 622 patients were assigned to accelerated, hypofractioned whole-breast irradiation at a dose of 42.5 Gy administered in 16 fractions over 22 days.

At 10-years follow-up, the cumulative incidence of local recurrence was 6.7% in the standard course group compared with 6.2% in the hypofractionated group (95% CI, -2.5 to 3.5).

The cumulative incidence of invasive or noninvasive local recurrence was 7.5% in the control group compared with 7.4% in the hypofractionated group (95% CI, -3.1 to 3.3). A subgroup analysis showed that the treatment effect was consistent regardless of patient age, tumor size, ER-status or systemic therapy.

The short-course hypofractionated regimen was less effective at treating high-grade tumors. Researchers said local recurrence was 4.7% in control group patients with high-grade tumors compared with 15.6% in the hypofractionated group patients with these tumors.

There were 82 cancer-related deaths in both groups. Ten-year probability for survival was 84.4% in the control group compared with 84.6% in the short-course group.

Whelan TJ. New Engl J Med. 2010;362:513-520.