The second ten years: long-term risks of breast conservation in early breast cancer.

A retrospective cooperative study was undertaken to analyze the fate of 300 clinical Stage I and II breast cancer patients who were alive and apparently cured with both breasts preserved, 10 years following primary limited surgery with irradiation. All patients had been treated by tumor excision, with or without axillary dissection, followed by megavoltage radiation therapy. Follow-up ranged from 10.5 to 26 years, median 14.5 years. The overall actuarial survival (Kaplan-Meier) of the 300 "cured" patients was 86% at 15 years and 78% at 20 years, with 38.5% of deaths attributable to breast cancer. The actuarial probability of remaining free of metastatic disease was 91% at both 15 and 20 years, independent of age or clinical stage. Sixteen patients (5.3%) developed recurrent cancer in the treated breast beyond the tenth year, the actuarial probability of remaining free of breast recurrence being 94% and 90% at 15 and 20 years, respectively. Contralateral breast cancers developed during the second decade in 5 patients, with a cumulative risk of 6.5% at 20 years. Significant treatment-related problems appeared during the second decade in 5 patients, including one chest wall sarcoma; all of these patients had received at least 60 Gy to breast and regional nodal areas. A comparison of these results with those in the literature allowed the following conclusions to be drawn: (a) the risk of death, as well as breast cancer mortality during the second decade, are similar for both conservatively and radically treated patients with Stage I and II breast cancer; (b) the risk of contralateral breast cancer is not greater than that observed following primary radical surgery without radiation therapy; (c) ipsilateral breast "recurrences" continue to occur at about 1% per year during the second decade. Such late recurrences are highly operable and have a favorable prognosis; (d) late progression of treatment-related sequelae is uncommon. This analysis supports the continued use of breast-conserving surgery with radiation therapy in the treatment of Stage I and II breast cancer.