MONDAY, Oct. 5, 2020 (HealthDay News) -- Research following patients for nearly three decades finds that surgery plus radiation beats surgery alone for women with ductal carcinoma in situ (DCIS) -- a common, early form of breast cancer that can become invasive cancer.
However, the study also found that any survival advantage for the combo treatment appears to fade over the long term.
Still, "overall, the addition of radiotherapy gives women the best chances," concluded study leader Maartje van Seijen of the Netherlands Cancer Institute. She presented the findings Saturday at the European Breast Cancer Conference, held online this year.
One U.S. breast surgeon called the new study a "great opportunity" to glean new insights about DCIS.
"This article is unique, in that it follows a very large number of women with DCIS over a very long time -- 10,045 women followed for 27 years," said Dr. Alice Police, who wasn't involved in the study. She's regional director of breast surgery at the Northwell Health Cancer Institute in Sleepy Hollow, N.Y.
"DCIS is a common form of very early breast cancer where the bad cells have not spread out of the milk ducts," Police explained. Because it is such an early form of breast cancers, there are concerns about "overtreatment," she said.
The new research sought to address those concerns. In the study, Dutch women were diagnosed with a DCIS between 1989 and 2004. They were then treated with either breast-sparing surgery (lumpectomy) to remove the DCIS; breast-sparing surgery followed by radiotherapy, or a full mastectomy.
In the first 10 years after diagnosis, women who had breast-sparing surgery alone had a 13% risk of being diagnosed with DCIS again and a 13.9% risk of invasive breast cancer.
In contrast, women treated with breast-sparing surgery plus radiotherapy had a 4.6% risk of recurrent DCIS and a 5.2% risk of invasive breast cancer, the researchers reported.
But the differences between the two groups of women grew smaller with time. Ten or more years after their DCIS diagnosis, women who had breast-sparing surgery only had a 1.2% risk of recurrent DCIS and an 11.8% risk of invasive breast cancer.
Over the same interval of time, women treated with breast-sparing surgery and radiotherapy had a 2.8% risk of recurrent DCIS and a 13.2% risk of invasive breast cancer, van Seijen's group said.
Women who had a mastectomy had the lowest risk of invasive breast cancer, the study found.
The findings clarify the long-term risks for women with DCIS and may help them and their doctors decide the best treatment for them, the study authors said.
"The risk of DCIS or invasive cancer recurring in these women will diminish over time, whether they had just the breast-sparing surgery or breast-sparing surgery with radiotherapy," van Seijen said in a conference news release. Radiotherapy seems to provide a bit more protection, at least over the shorter term.
"There remains a chance of a new DCIS or invasive cancer developing that is not related to the initial diagnosis and we would expect this risk to be similar between the two types of treatment," van Seijen added. "In a very small number of women, radiotherapy itself might cause a new breast cancer, often many years after the radiotherapy was given."
And while women who had a mastectomy had the lowest risk of invasive breast cancer, "it's important to remember that, according to previous research, overall survival in patients who have a mastectomy is the same as in patients who have less aggressive treatments. For the majority of women with DCIS, whose condition will never become invasive, mastectomy would be considered over-treatment," van Seijen said.
For her part, Police said that "this article confirms that DCIS should be treated with surgery and that the best way to avoid a recurrence is to add adjuvant radiation therapy."
And she agreed with van Seijen regarding that "the study does suggest that mastectomy should be considered unnecessary in women with DCIS who are otherwise eligible for breast conservation," Police said.
Findings presented at medical meetings are typically considered preliminary until published in a peer-reviewed journal.
Breastcancer.org has more on DCIS.