Even after 20 years of follow-up, breast conserving therapy is shown to have equivalent efficacy as mastectomy

Radical mastectomy was once the standard treatment for most breast cancer patients, but radiotherapy offered the promise of breast conserving therapies, and twenty years ago EORTC trial 10801 showed that breast conserving surgery followed by radiotherapy had equivalent efficacy as modified radical mastectomy as a loco-regional treatment for operable breast cancer.[1] At the ten year follow-up the loco-regional recurrence rate was significantly higher for patients receiving breast-conserving therapy, 20%, than for those receiving modified radical mastectomy, 12%, (P-value = 0.0097), but no significant difference was observed between patients receiving breast-conserving therapy or radical mastectomy with respect to time to distant metastases or overall survival.[2]

Results at a median follow-up of 22.1 years have now been reported in Lancet Oncology, and these have reconfirmed that patients above the age of 35 years with stage I-II breast cancer can be effectively treated with breast-conserving therapy.[3]

EORTC trial 10801 accrued 868 patients between 1980 and 1986, and of these 448 were randomized to receive breast-conserving therapy and 420 to receive modified radical mastectomy. There was no significant difference observed between breast-conserving therapy and modified radical mastectomy with respect to time to distant metastases (hazard ratio (HR) = 1.13; 95% confidence interval (CI) = 0.92 – 1.38; P = 0.23) or overall survival (HR =1.11; 95% CI = 0·94 – 1.33; P = 0.23). Cumulative incidence of distant metastases at 20 years was 42.6% (95% CI = 37.8% – 47.5%) for patients receiving modified radical mastectomy and 46.9% (95% CI = 42.2% – 51.6%) for patients receiving breast-conserving therapy. Overall survival at 20 years was 44.5% (95% CI = 39.3% – 49.5%) for patients receiving modified radical mastectomy and 39.1% (95% CI = 34.4% – 43.9%) for patients receiving breast-conserving therapy. No significant difference was observed between the two treatments in terms of time to distant metastases or overall survival in patients who were younger than 50 years old and those aged 50 years or older.

These results are certainly special in that such a long follow-up is not an everyday occurrence, and also because the higher rate of a loco-regional recurrence which was observed previously in the breast conserving therapy arm does not seem to have much effect on overall survival, even in light of this long follow-up. While a divergence of some curves at the end of the study period for the previous publication in fact prompted this update analysis, this analysis reassures that the conclusions remain the same.

Given that loco-regional treatments and adjuvant treatments have improved considerably over the 30 years since the study was initiated, this really shows that breast conserving therapy continues to be justified.

John Bean and Saskia Litière