RADIOTHERAPY FOR DCIS REDUCES LOCAL RELAPSE

March 27, 2012 — Radiotherapy after surgery for ductal carcinoma in situ (DCIS) can significantly reduce the risk for disease recurrence, even after 15 years.

According to data presented at the 8th European Breast Cancer Conference (EBCC-8), held in Vienna, Austria, radiotherapy reduced the risk by 50%, and there were comparable reductions in invasive and DCIS recurrences.

Most local recurrences occurred in the 5 years after treatment, and radiotherapy appears to have a continuing protecting effect with respect to DCIS recurrence, the researchers note. However, the protective effect for invasive recurrence appears to be temporary, and observed mainly in the 5 years after treatment.

"The most important outcome of the trial was overall survival and time to distant metastasis," emphasized lead author Mila Donker, MD, a research physician from the Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, in Amsterdam. "The reduction in local recurrence seen with radiation therapy did not translate to an improvement in overall survival or time to distant metastasis."

"In both groups, almost 90% of the patients were still alive after 15 years, and 92% did not experience distant metastasis," she explained during a press briefing held in advance of her presentation.

The trial was conducted under the auspices of the European Organisation for the Research and Treatment of Cancer (EORTC), and involved 1010 patients from 13 different countries. It started in 1986, recruited its last patient in 1996, and has one of the longest follow-ups to date of a large group of patients.

All patients underwent a complete excision of DCIS (<5 cm), and then 503 patients were randomized to receive no further local treatment (control group) and 507 were randomized to receive whole-breast radiotherapy (50 Gy in 25 fractions).

"We stopped collecting data last April, resulting in a follow-up of almost 16 years," said Dr. Donker. "One of the most important outcomes of the trial was local recurrence."

After 15.8 years, 82% of the patients did not experience a local recurrence (hazard ratio, 0.52; 95% confidence interval, 0.40 to 0.68). In contrast, 69% of patients who did not receive radiotherapy remained free from local recurrence.

"So more than 30% of patients have a local recurrence in the same breast," she explained.

The 15-year cumulative incidence of the recurrence of DCIS was higher in the control group than in the radiotherapy group (14.9% vs 7.5%). The same was true for invasive recurrence (15.5% vs 9.8%).

The protective effect of radiotherapy on local recurrence was similar in the 3 time periods studied. The hazard rate was lower in the radiotherapy group than in the control group during the first 5 years after treatment (2.0% vs 4.0%), during the 5 to 10 years after treatment (1.2% vs 2.0%), and 10 years or more after treatment (0.6% vs 1.3%).

In contrast, the effect of radiotherapy was seen primarily during the first 5 years after treatment for invasive recurrences.

In a subgroup analysis, 5 years after randomization, survival was the same in patients with and without DCIS recurrence, Dr. Donker pointed out. However, "patients who had an invasive recurrence had a mortality rate that was 18 times higher than those who did not have a recurrence or a DCIS recurrence," she said. "This underlines the need to prevent a local recurrence."

Without adjuvant radiotherapy, 1 in 3 women will experience a local recurrence, and half of those recurrences are invasive, she explained. Adjuvant therapy reduces this risk by a factor of 2 (P < .0001).

"This is an important long-term follow-up study," said David Cameron, MD, MRCP, professor of oncology at the University of Edinburgh, United Kingdom, and chair of the EBCC-8. "DCIS is a much more common diagnosis now than when this trial was run, so there are many patients whose care might be influenced by these data. These data also reiterate the importance of long-term follow-up in breast cancer, as patients can, sadly, develop a recurrence of their cancer many years after their initial treatment."

8th European Breast Cancer Conference (EBCC-8): Abstract 217. Presented March 22, 2012.