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Tumor-bed radiotherapy boost reduces DCIS recurrence risk



Giving a boost radiation dose to the tumor bed following breast-conserving surgery and whole breast irradiation (WBI) has been shown to be effective at reducing recurrence of invasive breast cancer, and now a multinational randomized trial has shown that it can do the same for patients with non–low-risk ductal carcinoma in situ (DCIS).

The results provide the first randomized trial data to support the use of boost radiation after postoperative WBI in these patients to improve local control,” wrote the authors, led by Boon H. Chua, PhD, from the University of New South Wales, Sydney.

Among 1,608 patients with DCIS with at least one clinical or pathological marker for increased risk of local recurrence, 5-year rates of freedom from local recurrence were 97.1% for patients assigned to received a tumor bed boost versus 92.7% for patients who did not receive a boost dose. This difference translated into a hazard ratio for recurrence with radiation boost of 0.47 (P < .001).

“Our results support the use of tumor-bed boost radiation after postoperative WBI in patients with non–low-risk DCIS to optimize local control, and the adoption of moderately hypofractionated whole breast irradiation in practice to improve the balance of local control, toxicity, and socioeconomic burdens of treatment,” the authors wrote in a study published in The Lancet.

The investigators, from cancer centers in Australia, Europe, and Canada, noted that the advent of screening mammography was followed by a substantial increase in the diagnosis of DCIS. They also noted that patients who undergo breast-conserving surgery for DCIS are at risk for local recurrence, and half of recurrences present as invasive disease.

In addition, they said, there were high recurrence rates in randomized clinical for patients with DCIS who received conventionally fractionated WBI without a tumor boost following surgery.

“Further, the inconvenience of a 5- to 6-week course of conventionally fractionated WBI decreased the quality of life of patients. Thus, tailoring radiation dose fractionation according to recurrence risk is a prominent controversy in the radiation treatment of DCIS,” they wrote.

Four-way trial

To see whether a tumor-bed boost following WBI and alternative WBI fractionation schedules could improve outcomes for patients with non–low-risk DCIS, the researchers enrolled patients and assigned them on an equal basis to one of four groups, in which they would receive either conventional or hypofractionated WBI with or without a tumor-bed boost.

The conventional WBI regimen consisted of a total of 50 Gy delivered over 25 fractions. The hypofractionated regimen consisted of a total dose of 42.5 Gy delivered in 16 fractions. Patients assigned to get a boost dose to the tumor bed received an additional 16 Gy in eight fractions after WBI.

Of the 1,608 patients enrolled who eligible for randomization, 803 received a boost dose and 805 did not. As noted before, the risk of recurrence at 5 years was significantly lower with boosting, with 5-year free-from-local-recurrence rates of 97.1%, compared with 92.7% for patients who did not get a tumor-bed boost.

There were no significant differences according to fractionation schedule, however: among all randomly assigned patients the rate of 5-year freedom from recurrence was 94.9% for both the conventionally fractionated and hypofractionated WBI groups.

Not surprisingly, patients who received the boost dose had higher rates of grade 2 or greater toxicities, including breast pain (14% vs. 10%; P = .03) and induration (14% vs. 6%; P < .001).

The study was supported by the National Health and Medical Research Council of Australia, Susan G. Komen for the Cure, Breast Cancer Now, OncoSuisse, Dutch Cancer Society, and Canadian Cancer Trials Group. Dr. Chua disclosed grant support from the organizations and others.

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