RTOG 9804 Trial Shows Reduced Local Failure With Radiotherapy After Breast-Conserving Surgery in Patients With Good-Risk DCIS
As reported in the Journal of Clinical Oncology by McCormick et al, the Radiation Therapy Oncology Group (RTOG) 9804 trial showed that radiotherapy after breast-conserving surgery reduced local failure vs observation in women with good-risk ductal carcinoma in situ (DCIS). The study was designed for a target of 1,790 patients but was closed early due to slow accrual.
Study Details
In the trial, 585 patients from the United States and Canada with mammographically detected low- or intermediate-grade DCIS, measuring < 2.5 cm with margins ≥ 3 mm, were randomly assigned between December 1999 and July 2006 to receive radiotherapy (n = 287) or observation (n = 298). Tamoxifen use was originally mandatory but was made optional in a protocol amendment. Ipsilateral local failure was the primary endpoint.
Patients had a median age of 58 years (80% aged ≥ 50 years) and median largest dimension of DCIS lesion on pathology slide of 0.5 cm. Most patients were white (79%–83%), had mammographic size of primary tumor of ≤ 1 cm (72%–73%), and had nuclear grade of 2 (56%–58%). Approximately 50.5% had right breast tumors. Microscopic margins were ≥ 3 to 9 mm in 36%, ≥ 10 mm in 16%, and negative in 48%. Tamoxifen use was intended by 69% of patients in both groups.
Reduced Local Failure Rate
Median follow-up was 7.17 years (range = 0.01–11.33 years). Overall, two local failures occurred in the radiotherapy arm, and 19 occurred in the observation arm. Cumulative local failure rates were 0.4% vs 3.5% at 5 years and 0.9% vs 6.7% at 7 years (hazard ratio [HR] = 0.11, P <.001). Risk of contralateral breast local failure at 7 years was 3.9% vs 4.8% (P = .88).
Overall, eight women in the observation group underwent mastectomy, including four unilateral mastectomies for ipsilateral failure, three bilateral mastectomies (for two ipsilateral failures and one bilateral failure), and one elective bilateral mastectomy. Four women in the radiotherapy group underwent mastectomy, including three bilateral mastectomies for ipsilateral failure, contralateral failure, and bilateral failure and one elective bilateral mastectomy. The 7-year cumulative incidence of mastectomy was 1.5% vs 2.8%.
At 7 years, disease-free survival was 88.0% vs 85.6% (P = .44) and overall survival was 91.7% vs 95.1% (P = .18).
Toxicity
Grade 1 or 2 acute toxicities occurred in 76% vs 30% of patients, and grade 3 or 4 toxicities occurred in 4.2% vs 4.0%. Late radiotherapy toxicity was grade 1 in 30% of patients, grade 2 in 4.6%, and grade 3 in 0.7%.
The investigators concluded: “In this good-risk subset of patients with DCIS, with a median follow-up of 7 years, the [local failure] rate was low with observation but was decreased significantly with the addition of [radiotherapy]. Longer follow-up is planned because the timeline for [local failure] in this setting seems protracted.”
Beryl McCormick, MD, of Memorial Sloan Kettering Cancer Center, is the corresponding author for the Journal of Clinical Oncology article.
The study was supported by grants from RTOG, Community Clinical Oncology Program, and National Cancer Institute. For full disclosures of the study authors, visit jco.ascopubs.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
