BS18
DCIS AND TREATMENT

Ductal carcinoma in situ now represents 30% of all screen detected breast cancers. Breast conserving surgery for ductal carcinoma in situ is now established although the extent of margin clearance necessary to prevent recurrence after breast conserving surgery remains controversial. None of the previous trials which compared radiotherapy with breast conserving surgery alone have achieved clear margin status in all patients and analysis of their data suggests that the recurrence rate when clear margins around the ductal carcinoma in situ are achieved is low (approximately 10% at six years). Data from randomised trials indicates that a margin of greater than 1 mm clearance is sufficient to minimise recurrence in the breast. Several centres have published that clear margins are essential in the management of ductal carcinoma in situ whether radiotherapy is used or not.Tamoxifen has been studied after wide local excision and radiotherapy in the NSABP24 trial and in the UK DCIS trial. In the former trial a 40% reduction in recurrence in the breast using tamoxifen was seen but the majority of this effect was in women under 50 years of age and only a marginal effect was seen in older patients. In the UK DCIS trial a 20% non‐significant reduction in recurrence was seen in women who were not given radiotherapy. Studies show that younger women (less than 50 years of age) have a significantly higher risk of recurrence after ductal carcinoma in situ treatment and tamoxifen is therefore recommended in women under 50 years of age who are undergoing wide local excision for ductal carcinoma in situ. Oestrogen receptor status was retrospectively assessed in the NSABP B24 trial and ER positive DCIS had a 60% reduction in recurrence whilst ER negative DCIS had no benefit. The BASO DCIS II trial assesses the benefit of adding radiotherapy in ER positive DCIS treated with 5 years Tamoxifen on local recurrence. Aromatase inhibitors are more effective in the presence of CerbB2 oncogene, which is frequently expressed in ductal carcinoma in situ and studies comparing aromatase inhibition with Tamoxifen in ductal carcinoma in situ are already underway (IBIS II). These studies should take account of oestrogen receptor status in the ductal carcinoma in situ to allow us to more adequately define the role of oestrogen receptor status in predicting response to therapy in patients with ductal carcinoma in situ.