A Cochrane review [Abstract] 1 included 4 studies with a total of 3925 women. 3 trials compared the addition of radiotherapy (RT) to breast conserving surgery (BCS). One trial was a two by two factorial design comparing the use of RT and tamoxifen, each separately or together, in which participants were randomised in at least one arm. A statistically significant benefit from the addition of RT on all ipsilateral breast events was confirmed (hazards ratio (HR) 0.49; 95% CI 0.41 to 0.58, 4 trials, n=3920), ipsilateral invasive recurrence (HR 0.50; 95% CI 0.32 to 0.76, 2 trials, n=1843) and ipsilateral ductal carcinoma in situ DCIS recurrence (HR 0.61; 95% CI 0.39 to 0.95, 2 trials, n=1843). All the subgroups analysed benefited from RT. No evidence of excess deaths attributable to the addition of RT, either due to vascular disease, pulmonary toxicity, or second malignancies or other significant long-term toxicity was found in follow-up from 4.4 years to 10.5 years.
A cohort study 2 included 140 366 patients with DCIS. 35 070 (25.0%) were treated with lumpectomy alone, 65 301 (46.5%) were treated with lumpectomy and radiotherapy, and 39 995 (28.5%) were treated with mastectomy. The actuarial 15-year breast cancer mortality rate was 2.33% for patients treated with lumpectomy alone, 1.74% for patients treated with lumpectomy and radiation, and 2.26% for patients treated with mastectomy. The adjusted hazard ratios for death were 0.77 (95% CI, 0.67 to 0.88) for lumpectomy and radiotherapy vs lumpectomy alone (29 465 propensity-matched pairs), 0.91 (95% CI, 0.78 to 1.05) for mastectomy alone vs lumpectomy alone (20 832 propensity-matched pairs), and 0.75 (95% CI, 0.65 to 0.87) for lumpectomy and radiotherapy vs mastectomy (29 865 propensity-matched pairs).
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