An Australia-led trial has defined a new standard of shorter courses of postoperative radiation therapy for women with DCIS, showing that hypofractionated therapy is appropriate for all patients.
The phase 3 study led by Professor Boon Chua and colleagues at the University of NSW showed that the ‘conventional’ schedule of five weeks of daily whole breast irradiation after breast conserving surgery can be replace with a shorter course of more intense but less frequent radiotherapy sessions with a tumour bed boost.
Published in The Lancet, the results from the international multicentre study involving more than 1600 patients with non-low-risk DCIS showed that a schedule of moderately hypofractionated whole-breast radio therapy (~2 ·7 Gy in 15–16 fractions) and a tumour bed boost was as effective in preventing recurrence as the ‘conventional’ schedule after almost seven years of follow up.
The researchers said that while the number of diagnosed DCIS cases had increased substantially since the implementation of mammographic screening, there was little evidence to date on whether the use of hypofractionated WBI and a bed boost would be effective in preventing recurrence as it was in invasive disease.
They therefore conducted a study that enrolled 1608 women from 136 participating centres in 11 countries, which randomised participants to either conventional or moderately hypofractionated postoperative radiotherapy with a tumour bed boot.
The participants were women with non-low-risk DCIS, which included being younger than 50 years, having symptomatic presentation or palpable disease, a tumour size of 15 mm or more, multifocality, an intermediate-grade or high-grade tumour, central necrosis or comedo histology, or surgical margins of less than 10 mm.
For the primary outcome of five-year freedom from local-recurrence, the rates were 97·1% with a boost compared with 92·7% with no boost.
The boost group had significantly higher rates of grade 2 or higher breast pain (10% vs 14%) and induration (6% vs 14%).
The absolute gain in local control with boost radiation was 4·4% at five years and less than half (44%) of local recurrences were invasive. The magnitude of these effects was similar to the effects at 20 years observed in a randomised trial evaluating boost radiation for invasive breast cancer, and the estimated effects at 15 years in a large retrospective analysis of pooled patients with DCIS, the researchers noted
They concluded that the results “support the use of tumour bed boost radiation after postoperative WBI in patients with non-low-risk DCIS to optimise local control, and the adoption of moderately hypofractionated WBI in practice to improve the balance of local control, toxicity, and socioeconomic burdens of treatment.”
An accompanying commentary stated that the results showed that hypofractionated whole-breast radiotherapy was appropriate for all breast cancer patients, including those with DCIS.
“Breast cancer patients should not receive five-week radiotherapy after breast-conserving surgery, and the term conventional radiotherapy in this context is obsolete,” they wrote
However, the authors said the benefits regarding a tumour bed boost were less clear, and suggested that treatment be tailored by identifying patients at a high risk of recurrence, where the benefits are likely to outweigh risks.
These could include symptomatic patients younger than 50 years with high-grade DCIS, they suggested.
“Health-care professionals should communicate potential risks and benefits adequately … many patients that are fully informed of the risks and benefits defined by this landmark trial might decide that less is more, and opt for no boost,” they concluded.