As reported in The Lancet by the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG), an individual patient meta-analysis has shown that more recent—but not older—trials of regional lymph node radiotherapy vs no radiotherapy in patients with early breast cancer showed benefits of radiotherapy.
Study Details
The study involved individual patient data from 14,324 women in 16 trials beginning before January 2009. The primary outcome measures were recurrence at any site, breast cancer mortality, non–breast cancer mortality, and all-cause mortality.
Regional node radiotherapy significantly reduced breast cancer mortality and all-cause mortality in trials done after the 1980s, but not in older trials. These contrasting findings could reflect radiotherapy improvements since the 1980s.— Early Breast Cancer Trialists' Collaborative Group (EBCTCG)
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Key Findings
In the eight more recent trials (starting in 1989 and thereafter and including 12,167 patients), median follow-up was 13.7 years (interquartile range [IQR] = 9.9–16.0 years). Regional node radiotherapy was associated with a significantly reduced risk of recurrence (rate ratio [RR] = 0.88, 95% confidence interval [CI] = 0.81–0.95, P= .0008). Few regional node recurrences were reported, with the primary effect being reduced risk for distant recurrence (RR = 0.86, 95% CI = 0.80–0.93, P = .00026). Radiotherapy vs no radiotherapy was associated with a significant reduction in breast cancer mortality (RR = 0.87, 95% CI = 0.80–0.94, P = .0010), no significant effect on non–breast cancer mortality (RR = 0.97, 95% CI = 0.84–1.11, P = .63), and a significant reduction in all-cause mortality (RR = 0.90, 95% CI = 0.84–0.96, P = .0022).
In the eight older trials (starting in 1961 to 1978 and including 2,157 patients), median follow-up was 25.6 years (IQR = 12.4–41.7 years). Regional node radiotherapy vs no radiotherapy was associated with no effect on breast cancer mortality (RR = 1.04, 95% CI = 0.91–1.20, P = .55), a significant increase in non–breast cancer mortality (RR = 1.42, 95% CI = 1.18–1.71, P = .00023), and a significant increase in all-cause mortality (RR = 1.17, 95% CI = 1.04–1.31, P = .0067). Increased risk of non–breast cancer mortality was particularly evident after more than 15 years of follow-up.
The investigators concluded, “Regional node radiotherapy significantly reduced breast cancer mortality and all-cause mortality in trials done after the 1980s, but not in older trials. These contrasting findings could reflect radiotherapy improvements since the 1980s.”
EBCTCG secretariat, Clinical Trial Service Unit, Nuffield Department of Population Health, Oxford, UK, is the corresponding entity for The Lancet article.
Disclosure: The study was funded by Cancer Research UK and Medical Research Council. For full disclosures of the study authors, visit thelancet.com.
