Breast relapse following primary radiation therapy for early breast cancer. I. Classification, frequency and salvage.

Primary radiation therapy has become an accepted alternative to mastectomy for patients with early breast cancer. In order to improve the results of this treatment, we performed an analysis of failure on 366 clinical Stage I or II invasive breast carcinomas treated with primary radiation therapy. With a median follow-up of 52 months, there have been 30 recurrences in the treated breast, for a 5 year actuarial local recurrence rate of 9%. The recurrence rate was much higher for patients having less-than-excisional biopsy than for those undergoing excisional biopsy (35% vs. 7%, p less than 0.0001). Failures in the treated breast have been categorized as: true recurrence (TR), directly at the site of the primary; marginal miss (MM), at the edge of the boosted volume; and elsewhere in the breast (E). For patients having excisional biopsy, the actuarial probability of a true recurrence at 5 years was 4%. The risk of a true recurrence was related to the dose given to the primary site with rare true recurrences seen with doses greater than 6000 rad. The probability of a marginal miss at 5 years was 4%, and was not related to the dose or volume of the boost used. The probability of a recurrence elsewhere in the breast at 5 years was 1%. In patients treated with excisional biopsy and a total primary dose over 6000 rad, the probability of a local recurrence at 5 years was 4 and 10% for clinical Stage I and II patients respectively. These results indicate that primary radiation therapy provides a high likelihood of local tumor control and our analysis of failure suggests methods for decreasing each type of local recurrence.