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Effect of Postmastectomy Radiation Therapy in Node-Positive Breast Cancer

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Key Points

  • Postmastectomy radiation therapy was associated with a lower 10-year risk of locoregional recurrence.
  • No difference in 10-year breast cancer–specific or overall survival was observed with postmastectomy radiation therapy.  

In an analysis of data from the Breast International Group (BIG) 02-98 trial reported in the International Journal of Radiation Oncology*Biology*Physics, Zeidan et al found that postmastectomy radiation therapy (PMRT) vs no PMRT was associated with significantly reduced risk of locoregional recurrence in women with T1-T2 breast cancer and one to three positive nodes. PMRT was not associated with differences in 10-year cancer-specific or overall survival.

Study Details

In the BIG 02-98 trial, 2,887 patients with invasive breast cancer (clinical stage T1–3) who underwent surgical resection (mastectomy or breast-conserving surgery) with negative margins and had at least 1 positive axillary lymph node were randomized to receive adjuvant anthracycline with or without taxane chemotherapy. PMRT was performed according to institutional preference.

The current analysis assessed 10-year outcomes among 684 patients with T1–T2 disease and 1 to 3 positive lymph nodes who underwent mastectomy and axillary nodal dissection, including 337 (49%) who received PMRT. The primary outcome of interest was locoregional recurrence.

10-Year Outcomes

At 10 years, the risk of locoregional recurrence was 2.5% in the PMRT group vs 6.5% in the no-PMRT group (hazard ratio [HR] = 0.29, P = .005).  Among patients who received adjuvant chemotherapy with no taxane, the 10-year locoregional recurrence rate was 3.4% in the PMRT group vs 9.1% in the no-PMRT group (HR = 0.20, P = .02); among those receiving taxane-based adjuvant therapy, rates were 2.0% vs 5.3% (HR = 0.37, P = .08).

The 10-year distant recurrence-free survival rate was 77.3% vs 75.9% (HR = 1.10, P =.59). No significant differences between the PMRT group and the no-PMRT groups were observed for 10-year breast cancer–specific survival (84.3% vs 83.9%, HR  = 0.98, P = .91) or 10-year overall survival (81.7% vs 78.3%, HR = 0.87, P = .47).

The investigators concluded, “Our analysis of the BIG 02-98 trial shows excellent outcomes in women with T1–2 tumors and [one to three] positive lymph nodes found in axillary dissection. Although PMRT improved [locoregional recurrence] in this cohort, the number of events remained low at 10 years. In all groups, 10-year rates of [locoregional recurrence] were relatively low compared with historical studies. As such, the use of PMRT in women with [one to three] positive nodes should be tailored to individual patient risks.”

The study was funded by Sanofi-Aventis and by grants from the National Health and Medical Research Council to Breast Cancer Trials Australia & New Zealand.

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®.


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