Mammographic breast screening (introduced in the UK National health Service in 1988) has led to an increase in the diagnosis of DCIS. Controversy surrounds the treatment of DCIS-mastectomy is often considered to be too drastic, whilst removing the duct without additional treatment may not be deemed sufficient management.
David George from Glasgow's Western Infirmary, UK, and colleagues investigated whether additional treatment with tamoxifen, or radiotherapy, or both tamoxifen and radiotherapy, could reduce recurrence of breast cancer after surgery to remove DCIS in around 1700 women from the UK, Australia, and New Zealand.
Average follow-up was around four and a half years. Radiotherapy after surgery reduced the relative risk of recurrent DCIS in the same breast by over 60%, and decreased the overall relative risk of invasive cancer in the same breast by over 50%. Tamoxifen reduced the relative risk of DCIS recurrence by around 30% but had no effect in reducing the risk of invasive cancer in the same breast. Neither treatment had any effect on the cancer risk in the other breast.
Co-author Joan Houghton comments: "These results are important because many surgeons, especially in the UK, think that radiotherapy is not required if the disease is completely removed in surgery. However, we will have to await the results of our more detailed study of the pathological characteristics of the removed tissues before we can confirm that radiotherapy is useful for all patients. In terms of the number needed to treat, our results indicate that in patients with DCIS detected by mammography, treatment of 36 women with a five-week course of radiotherapy will prevent the development of an invasive tumour in the ipsilateral breast of one woman in the first 5 years of follow-up. Our results do not lend support to the use of tamoxifen in women older than 50 years with DCIS."
Jack Cuzick (also a study investigator) comments: 'Although this study has reinforced the importance of radiotherapy for DCIS, new studies of radiotherapy in selected patients will help to define more precisely which women need radiotherapy. It is also important to study the role of the newer hormonal treatments such as anastrozole; the IBIS-II trial is doing this.
Contact: Mrs Joan Houghton, Clinical Trials Group, Department of Surgery, Charles Bell House, 67-73 Riding House Street, London W1W 7EJ, UK; T)+44-0-20-7679-9679; F)+44-0-20-7679-9678; E) j.houghton@ctg.ucl.ac.uk.
Journal
The Lancet