As reported in The New England Journal of Medicine by Ian H. Kunkler, MB, BChir, MA, FRCR, and colleagues, the phase III PRIME II trial has shown a higher risk of local recurrence with the omission of adjuvant radiotherapy after breast-conserving surgery in patients aged ≥ 65 years with hormone receptor–positive, node-negative disease who were receiving adjuvant endocrine therapy. No difference in the risk of distant recurrence as the first recurrence event or overall survival was observed.
Ian H. Kunkler, MB, BChir, MA, FRCR
Study Details
The trial included 1,326 patients from sites in the United Kingdom (n = 1,263), Greece, Australia, and Serbia with T1 or T2 primary breast cancer (with tumors ≤ 3 cm in the largest dimension) who received breast-conserving surgery with clear excision margins and adjuvant endocrine therapy. Patients were randomly assigned between April 2003 and December 2009 to whole-breast irradiation at 40 to 50 Gy in 20 to 25 fractions (n = 658) or no irradiation (n = 668). Tamoxifen at 20 mg per day for 5 years was recommended as standard adjuvant endocrine therapy. The primary endpoint was local breast cancer recurrence.
Key Findings
Median follow-up was 9.1 years. At 10 years, the cumulative incidence of local recurrence was 9.5% (95% confidence interval [CI] = 6.8%–12.3%) in the no-radiotherapy group vs 0.9% (95% CI = 0.1%–1.7%) in the radiotherapy group (hazard ratio = 10.4, 95% CI = 4.1–26.1, P < .001). The 10-year cumulative incidence of distant recurrence as the first recurrence event was 1.6% (95% CI = 0.4%–2.8%) in the no-radiotherapy group vs 3.0% (95% CI = 1.4%–4.5%) in the radiotherapy group.
For the no-radiotherapy group vs the radiotherapy group, 10-year rates were:
- 68.9% (95% CI = 64.7%–73.0%) vs 76.3% (95% CI = 72.5%–80.2%) for disease-free survival
- 80.8% (95% CI = 77.2%–84.3%) vs 80.7% (95% CI = 76.9%–84.3%) for overall survival
- 97.4% (95% CI = 96.0%–98.8%) vs 97.9% (95% CI = 96.5%–99.2%) for breast cancer–specific survival.
The investigators concluded, “Omission of radiotherapy was associated with an increased incidence of local recurrence but had no detrimental effect on distant recurrence as the first event or overall survival among [patients] 65 years of age or older with low-risk, hormone receptor–positive early breast cancer.”
Dr. Kunkler, of the Institute of Genetics and Cancer, the University of Edinburgh, is the corresponding author for The New England Journal of Medicine article.
Disclosure: The study was funded by the Chief Scientist Office of the Scottish Government and the Breast Cancer Institute, Western General Hospital, Edinburgh. For full disclosures of the study authors, visit nejm.org.
