Outcome of radiotherapy after breast conserving surgery in screen detected breast cancers

The treatment outcomes were reviewed for all the patients at this institute who underwent breast irradiation after breast conserving surgery in 1991. Of a total of 643 patients treated, 194 (30%) had presented with tumours detected by screening mammography. The breast was irradiated with a tangential pair of fields, giving a dose of 40 Gy in 15 fractions over 3 weeks in 97% of these patients. A boost was not used. With a median follow-up of 4.7 years, there was better cancer related survival in patients with screen detected cancers compared with those that were non-screen detected (94% versus 84% at 5 years; P = 0.002). The breast recurrence rate at 5 years was 1% for screen detected cancers compared with 6% for those that were non-screen detected (P = 0.01). Factors additional to screen detected status that were found to be significant for cancer survival were pathological stage (P = 0.03) and histological grade (P = 0.01), In a Cox multivariate analysis, only two factors were significant for breast recurrence: screen detected status (P = 0.023) and histological grade (P = 0.016) This study suggests that breast irradiation with 40 Gy given over 3 weeks after breast conserving surgery for screen detected breast cancer gives a high level of local control out to 5 years.