Tamoxifen Has Favorable Effect on Recurrences in DCIS

San Antonio, TX—An updated analysis of the UK/ANZ DCIS trial reveals a beneficial effect of tamoxifen on breast cancer recurrences at 10 and 15 years of follow-up in women with ductal carcinoma in situ (DCIS), reported Jack Cuzick, PhD, at the CTRC-AACR San Antonio Breast Cancer Symposium. The updated analysis also confirms the benefit of radiotherapy on tumor recurrence. “The effects of tamoxifen appear to be substantially larger in low- and intermediate-grade lesions, whereas radiotherapy works right across the board,” he said.

In UK/ANZ DCIS, 1694 evaluable patients with DCIS were randomized to receive radiotherapy, tamoxifen, or both. The median follow-up now extends to 12.7 years, at which time radiotherapy was associated with a 68% reduction (14.6% absolute reduction) in the time to ipsilateral invasive disease (P <.0001) and a 62% reduction in the time to ipsilateral DCIS (P <.0001). There was no significant effect of radiotherapy on contralateral disease.

Overall, new breast cancer events were reduced by 59% in women randomized to radiotherapy compared to no radiotherapy (P <.0001). Patients randomized to tamoxifen had no significant decrease in the time to any recurrence compared to patients not randomized to tamoxifen at 5 years, as previously reported, but “there is a striking separation of the [event] curves with longer follow-up,” said Dr Cuzick, head of Cancer Research UK Centre for Epidemiology, Mathematics and Statistics, London, United Kingdom.

By year 15, tamoxifen reduced all recurrences by 29% (P =.002); this reflects a 30% reduction in recurrent ipsilateral DCIS, a nonsignificant 5% reduction in recurrent ipsilateral invasive disease, and a 56% reduction in contralateral tumors. “There was a somewhat larger effect [of tamoxifen] for DCIS versus invasive contralateral tumors,” he said.

On any breast cancer event, Dr Cuzick said, “the effect of tamoxifen was much stronger in low- and intermediate-grade tumors and potentially less effective in high-grade tumors.” He added that “there was no clear relationship of the effect of radiotherapy with grade. There was some variation across grades, but, in fact, there was no obvious trend, with substantial reductions of about two-thirds in all grades of DCIS.”

No significant difference in overall death was observed between any of the groups, although there were numerically more deaths in the group treated with both radiotherapy and tamoxifen than in the other groups. “This is not surprising. We know that DCIS is a disease with low mortality, and this confirms no adverse or positive effects of treatment on mortality at this stage,” said Dr Cuzick.