Which adjuvant treatment for DCIS best prevents recurrence at 12-year follow-up?

This article reports long-term results of the UK/ANZ DCIS (“UK/Australia and New Zealand Ductal Carcinoma in Situ”) trial. This study investigated the use of radiation treatment and Tamoxifen treatments in DCIS.

Ductal carcinoma in situ (DCIS) is the most common type of non-invasive breast cancer. "In-situ" means the cancer is still in its original location. DCIS itself is not immediately life threatening but it does increase the chances of later developing an invasive cancer.

In general, patients with DCIS have no symptoms. The number of detected DCIS cases has greatly increased over the past 20 years. DCIS represents approximately 10% of all breast cancers and 20% of those detected during screening.

DCIS is either high grade (fast growing) or low grade (slow growing). Treatment of DCIS generally involves removing the cancerous tissue along with some of the healthy tissue surrounding it, a procedure called ‘lumpectomy’. Surgery is often followed by radiation treatment to kill any cancer cells remaining after surgery. Some patients also receive hormone therapy, usually with Tamoxifen. Any additional post-operative treatment is referred to as ‘adjuvant therapy’.

The UK/ANZ DCIS study was conducted between 1990 and 1998 and involved 1694 women. They were followed-up for an average of 12.7 years to determine if they had breast cancer recurrence. The patients in this study all had their DCIS treated by local excision (lumpectomy). They were then treated with radiotherapy alone, tamoxifen alone, a combination of both radiotherapy and tamoxifen, or no post-operative treatment.

The study showed that during the follow-up period 376 breast cancers were diagnosed. Of these, 197 were DCIS, 174 in the same breast and 17 in the opposite breast. There were also 163 cancers that had spread outside the milk ducts (invasive), 122 cases in the same breast as the original DCIS and 39 cases in the opposite breast.

Overall, there were fewer recurrences of invasive cancers and DCIS in the same breast in patients treated with post-operative radiotherapy. There was no effect on the number of recurring cancers in the opposite breast. Treatment with Tamoxifen reduced the number of new DCIS cancers in both breasts, but had no effect on the number of new cases of invasive cancers in the same breast.

This article confirms that radiotherapy and Tamoxifen have long-term beneficial effects when used as adjuvant treatment for DCIS following lumpectomy.

It is however important to balance potential benefits with potential side effects of treatment.