ABSTRACT
The introduction of breast screening has resulted in a substantial increase in the diagnosis of ductal carcinoma in situ (DCIS). The characteristics of DCIS detected via screening are less aggressive than in women who present with symptomatic disease. Approximately 20% of cases will be upgraded to invasive disease after surgical excision, and although the rate of progression of DCIS if left untreated is uncertain, it is thought to be relatively low even after several decades. Treatment therefore needs to be tailored to avoid overtreatment for a disease which rarely causes death but upstages to invasive disease in half of all recurrences. Breast cancer–related mortality after a diagnosis of screen-detected DCIS is ∼2% higher than in women in the general population on long-term follow-up. Local treatment with mastectomy or breast-conserving surgery with or without adjuvant radiotherapy helps provide local control. Similarly, adjuvant anti-oestrogens help reduce rates of local recurrence and contralateral disease. The UK, Australia, and New Zealand Ductal Carcinoma In Situ (UK/ANZ DCIS) trial (and the similar National Surgical Adjuvant Breast and Bowel Project [NSABP] B-24 trial) explored the impact of radiotherapy and anti-oestrogen therapy, and also the combination of both, in women with screen-detected DCIS treated with breast conservation surgery.
