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Radiotherapy benefits good-risk patients with DCIS after breast-conserving surgery
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Radiotherapy may reduce the rate of local failure in patients with good-risk ductal carcinoma in situ, offering a better alternative to observation, according to results of a prospective, randomized, multi-institutional trial.
Although ductal carcinoma in situ (DCIS) is not considered life-threatening, a proactive approach toward eradicating it early may become a new standard if the findings of this trial can be confirmed, researchers wrote.
Beryl McCormick
“DCIS of the breast is a cancer that has captured my professional imagination for decades,” Beryl McCormick, MD, chief of the external beam radiotherapy service at Memorial Sloan Kettering Cancer Center, told HemOnc Today. “Unlike any other solid tumor that we treat, the local treatment and outcome have no effect on the distant disease-free survival of the patient. So, despite several large prospective trials — all designed to compare whole-breast radiation to breast conservation surgery alone, which showed a reduction in the risk of a local breast recurrence by 50% or more, and concluded that radiation is the ‘standard of care’ for this cancer — many oncologists who treat breast cancer hypothesized that the ‘standard of care’ was overtreatment for some women with this diagnosis.”
In their study, McCormick and colleagues aimed to evaluate the benefit of radiotherapy after surgery compared with observation.
The analysis included 636 patients aged at least 26 years (median age, 58 years) from the United States and Canada with mammographically detected low- or intermediate-grade DCIS measuring less than 2.5 cm with margins of at least 3 mm.
About two-thirds (62%) of patients in the study received tamoxifen, but they had to start that regimen within 4 weeks of diagnosis to eligible for inclusion.
Median follow-up was 7.17 years (range, 0.01-11.33 years).
During the trial, two local failures occurred in the radiotherapy arm vs. 19 local failures in the observational arm.
The rate of local failure at 7 years was 0.9% in the radiotherapy group (95% CI, 0.0-2.2) vs. 6.7% (95% CI, 3.2-9.6) in the observation group (HR = 0.11; 95% CI, 0.03-0.47).
The risk for contralateral breast failure at 7 years also was lower in the radiotherapy arm than the observation arm (3.9% vs. 4.8%; HR = 1.07; 95% CI, 0.48-2.39).
Researchers reported a higher rate of toxicity in the radiotherapy arm than the observation arm (76% vs. 30%; P < .001). However, serious toxicities (grades 3-5) occurred in 4% of patients in each arm.
Thirty percent of patients developed grade 1 late radiotherapy toxicities. A small percentage of patients experienced late radiotherapy toxicities that were grade 2 (4.6%) or grade 3 (0.7%).
“The trial results at 7 years show an extremely low rate of local failure in either arm, with the anticipated excellent survival rates,” McCormick said. “For my practice, this is the best evidence available to discuss ‘no radiation required’ for women who present with this low-risk DCIS. I’m often asked if patient age or tamoxifen use or another factor predicted for those cases with a local failure. For now, the answer is simply, ‘[There are] not enough events in either treatment arm.’” – by Anthony SanFilippo
For more information:
Beryl McCormick, MD, can be reached at Memorial Sloan Kettering Cancer Center, 1275 York Ave., New York, NY 10065
Disclosure: The researchers report various financial relationships with 21st Century Oncology, Bayer Healthcare, Breast Cancer Research Foundation, Genomic Health, Gerson Lehrman Group, Lightpoint Medical, Qfix, Radiological Associates of Sacramento, Roche, Varian and Zeiss.
Perspective
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As oncologists of all stripes — radiation, surgical, and medical — we are always trying to reduce the toxicity of our therapies while maintaining benefit and minimizing harm. The study by McCormick and colleagues addressed the question of whether external beam radiation was needed after segmental mastectomy for “good-risk” DCIS. The trial was planned for 1,790 patients but closed early due to poor accrual.
The analysis included 636 patients with DCIS with good-risk features (tumor < 2.5 cm, margins ≥ 3 mm, and low or intermediate tumor grade). Researchers randomly assigned patients to external beam radiation or no radiation. Use of tamoxifen was optional, but 62% of the patients received it.
At 7 years of follow-up, local failure rates were 0.9% with radiation and 7.6% without radiation. It is not clear whether this increased rate of local failure increased mortality (the study will continue follow-up to determine this). These results were consistent with results of other trials that selected patients with “good-risk" features, but lower that those trials — such as NSABP B17 — that did not select patients based on risk criteria. It is notable that none of these trials showed an increased mortality among patients who did not receive radiation.
So what do we do? At this point, it is at least reasonable to have the discussion of the risks and benefits of external beam radiation with women who have a diagnosis of DCIS with good-risk features. Some women may be satisfied with a watch-and-wait approach, understanding the increased risk of local recurrence.
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