Active monitor is safe for low-risk breast cancer DCIS

CANCER DIGEST – Dec. 29, 2024 – Women who carefully monitor their precancerous ductal carcinoma in situ are no more likely to develop breast cancer after two years than women who undergo surgery to remove the precancerous lesion, a new study shows.

Stage zero or precancerous ductal carcinoma in situ (DCIS) identifies abnormal cells within the milk ducts. Currently, almost all women with such lesions are treated with surgery to remove them to prevent development of more invasive cancer that can spread outside the breast. DCIS accounts for about 20 percent of all breast cancer diagnoses in the U.S. affecting nearly 60,000 women every year, according to the American Cancer Society.

Depending  on personal factors, it is estimated that between 50-80 percent of DCIS never go on to develop invasive cancer. Consequently, researchers led by Shelley Hwang, MD at the Duke Cancer Institute conducted a study to determine if women with stage 0 DCIS could safely forgo surgery to remove their precancerous lesions. 

The COMET study involved 1,000 women ages 40 and up who underwent biopsy to confirm DCIS. They were randomly assigned to standard surgery or to active monitoring involving imaging and exams every six months. The results were first presented at the San Antonio Breast Cancer Symposium and published in the Dec. 12, 2024 Journal of the American Medical Association (JAMA).

After two years of following the women, it turned out that 5.9 percent of the women in the surgery group went on to develop invasive cancer compared to 4.2 percent of the women in the active monitoring group. Hwang noted that the higher rate among the surgery group could be a result of finding the cancer to be invasive during surgery. Another factor was that while taking hormone blockers during the monitoring phase was optional, it turned out that most of the women in the monitoring group did so.

“We noted there were fewer cancers diagnosed in those patients who had active monitoring, and we feel that part of this was due to the hormone blocking treatment that many of them had,” Hwang said in a press release. “Although this was optional on the study, over 70 percent of women combined active monitoring with endocrine therapy, suggesting that this may be an important part of active monitoring in the future for women with DCIS."

Hormone blockers include a class of drugs called SERMs, which block estrogen receptors, and a class of drugs called aromatase inhibitors (AIs). Both drug classes are routinely prescribed following breast cancer treatments and have been shown to reduce recurrence of invasive cancer by approximately 50 percent.

Whether the standard of treatment for patients diagnosed with DCIS will change or not depends on further studies to confirm this study’s results.

Sources: DukeHealth press release and Dec. 12, 2024 JAMA