The Lynx Group

Radiation Boost Improves Local Control, Spares Salvage Mastectomy in Patients with Ductal Carcinoma in Situ

October 2016, Vol 7, No 9

Boston, MA—Using a radiation boost to the local tumor bed after surgery and radiation for ductal carcinoma in situ (DCIS) improves local control, according to the results of a study presented at the 2016 American Society for Radiation Oncology annual meeting.

Pooling data from 10 academic centers in North America and France, Meena S. Moran, MD, Director, Breast Cancer Radiotherapy Program, Yale School of Medicine, New Haven, CT, and colleagues demonstrated the same magnitude of local control in DCIS that has been reported for invasive breast cancer with a radiation boost postsurgery and radiation. Use of a radiation boost spares women from needing a mastectomy if the disease recurs in the same breast, making this practice of value.

Although a radiation boost is common practice in patients with DCIS who undergo surgery and radiation, this study provides the first robust data to support it.

“We have excellent data showing that a radiation boost of an additional 4 to 8 fractions provides a small but statistically significant reduction in the risk of ipsilateral breast tumor recurrence [IBTR] following invasive cancer....This study provides convincing evidence that a radiation boost achieves a similar level of risk reduction for patients with DCIS as it does for patients with invasive breast cancer,” stated lead investigator Dr Moran, who presented the study results.

According to studies in invasive breast cancer, the boost reduces the risk for local recurrence by 4% at 20 years, Dr Moran told attendees. Because DCIS has such a good prognosis, it would be challenging to try to conduct a randomized trial to prove that a boost of radiation was effective. Large numbers of patients with long follow-up would be necessary, Dr Moran explained.

This study is the largest data set on DCIS to date, with a total of 4131 patients with DCIS treated with breast-conserving therapy (ie, surgery plus radiation) with and without a radiation boost. Of these, 2661 patients had a boost, and 1470 had no boosts. The boost was more common in cases of positive surgical margins (4% of the total number of patients), unknown estrogen receptor status, and the presence of necrosis in the pathology report.

At a median follow-up of 9 years, the boost significantly decreased the risk for IBTR (P = .010). At 5 years, the rate of IBTR-free survival was 97.1% for the boost group versus 96.3% for the no-boost group. At 10 years, the rates of IBTR recurrence were 94.1% versus 92.5%, respectively, and by 15 years, the rates were 91.6% versus 88.0%, respectively.

Receiving a radiation boost significantly improved IBTR recurrence in women aged ≥50 years (P = .0073), and in younger women (<i>P</i> = .0166).

“Data on invasive breast cancer show that the 4% benefit over 20 years for boost reduced the rate of salvage mastectomy for recurrence by 40%. These data support use of a boost for women with DCIS who have life expectancies of 10 to 15 years, and who are receiving radiation therapy as part of their treatment plan,” Dr Moran stated.

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