Radiotherapy treatment (RT) after surgery for ductal carcinoma in situ (DCIS) has a major protective effect against recurrence more than 15 years later, according to the results of an international trial presented March 22 at the 8th European Breast Cancer Conference (EBCC-8).
Mila Donker, MD, of The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital in Amsterdam, and colleagues found that the use of RT in addition to surgery could reduce the chances of a local recurrence by 50 percent.
The researchers analyzed the 15-year follow-up of more than 1,000 DCIS patients. A total of 50 percent of the women had received RT after total surgical excision of a tumor of less than 5cm diameter and 50 percent had not.
When radiotherapy had not been given, almost one in three women had developed a local recurrence, while the 50 percent risk reduction in those patients who had had RT held true for both an in-situ and an invasive cancer recurrence.
The 15-year cumulative incidence for DCIS recurrence in the surgery group was 14.9 percent, as opposed to 7.5 percent in those patients in the surgery plus radiotherapy group. For an invasive recurrence the rates were 15.5 percent in the surgery only group and 9.8 percent in the combined group.
Although no survival difference was seen between the surgery alone and the surgery plus RT group, women who had an invasive recurrence had a significantly worse survival compared with those who had a DCIS recurrence or no recurrence at all.
"We found that the majority of the DCIS recurrences occurred within five years of treatment, and that RT seemed to have a continuous protective effect on DCIS recurrence in the long term," Donker said in a statement. "However, the protective effect of radiotherapy on the onset of invasive recurrence seemed to be observed mainly in the first five years after treatment, while the risk of developing a recurrence was more or less continuous over the years."
The number of DCIS cases has increased in the past few decades, and it now accounts for about 25 percent of all new breast cancer diagnoses.
Donker noted the importance of examining the biological behavior and malignant potential of DCIS. Such information could help researchers and physicians better understand over treatment of tumors that would not develop into a life-threatening cancer. “Our study provides convincing evidence that early treatment does work, and that it can help to avoid the more severe therapies that might be needed at a later stage," she said.
The next step for the researchers is to analyze prognosis and treatment after recurrence.
Donker and colleagues believe that their findings will allow them to better select patients who will benefit from particular treatments and avoid over and under treatment of patients with DCIS. "For example, in the future we will be able to identify patients who will not benefit from RT and spare them a treatment that might induce other tumors later in life. Or we could identify patients who need a more aggressive therapy than only local excision and RT—patients with a high chance of recurrence might benefit from an initial mastectomy, for example.”