Breast-conserving surgery paired with the estrogen-blocking drug tamoxifen reduced the chances of low-risk ductal carcinoma in situ (DCIS), a non-invasive breast cancer, from recurring in the same breast, according to findings drawn from two large consortium clinical trials.
The data are being presented at the San Antonio Breast Cancer Symposium on Thursday, Dec. 12, 2024.
The current standard of care for most DCIS cases is surgery followed by either radiation or estrogen blockers. A patient’s recurrence risk and treatment preference can determine whether some opt for breast-conserving surgery while others choose to have a mastectomy, and this can influence the approach to the care provided.
In this analysis of 878 participants who formed a subset of those enrolled in either the NRG/RTOG 9804 or the ECOG-ACRIN E5194 clinical trials and did not receive radiation, the researchers found that post-surgical DCIS patients with a “good risk” who received tamoxifen were 44% less likely to have any recurrence of cancer in their treated breast compared to those who didn’t receive tamoxifen. In addition, 51% were less likely to have an invasive recurrence compared to patients who did not take tamoxifen. This study confirms the ability of post-surgical tamoxifen to reduce an invasive recurrence in the absence of radiotherapy.
“This finding expands the menu of reasonable options for people with DCIS and provides patients, in consultation with their health care provider, better evidence to make informed shared decisions about reducing recurrence risk versus dealing with potential side effects from tamoxifen use,” said Jean L. Wright, MD, FASTRO, who presented the findings on behalf of her study colleagues. “The side effects and duration of hormone therapy versus radiation therapy are very different, so one treatment type may make more sense for one person but not another.”
Wright conducted the research while she was on faculty at Johns Hopkins University. She became chair of the department of radiation oncology at the University of North Carolina School of Medicine and the UNC Lineberger Comprehensive Cancer Center in Chapel Hill in August.
Recurrence occurs in 10–15% of patients who receive optimal treatment for DCIS; half of these recurrences are similar to the original occurrences, and half are invasive disease diagnoses. In the U.S., DCIS accounts for 20–25% of all breast cancer diagnoses. Fortunately, almost all DCIS recurrences can be successfully treated, but many patients prefer to reduce their risk of having a recurrence that requires additional treatment by opting for post-operative therapies like tamoxifen and radiation.
These findings are based on a nearly 15-year median follow-up of women who enrolled in the NRG/RTOG 9804 and ECOG-ACRIN E5194 trials in the early 2000’s. According to Wright, these trials are still quite relevant as there has been less change over the last 20 or more years in how DCIS is managed and treated compared to most other breast cancer diagnoses. Surgery remains the primary standard of care for DCIS, though studies are ongoing to evaluate non-surgical management of DCIS.
The NRG/RTOG 9804 and ECOG-ACRIN E5194 trials assigned women who had breast conservation surgery to different risk groups based on the size of their DCIS, the pathologic grade, and the degree to which a surgeon was confident they removed all of the DCIS. NRG/RTOG 9804 randomly assigned patients who had “good risk” DCIS, defined as being less than or equal to 2.5 centimeters in size, grade 1-2, and having no visible evidence of remaining DCIS, to receive whole breast radiation or no radiation. ECOG-ACRIN E5194 assessed patients in a similar manner but did not incorporate people who had radiation therapy.
“Genomic assays are becoming available and may be able to predict the benefit of various therapies better than our current use of traditional clinical and pathologic factors,” Wright said. “The next important studies, which our national cooperative groups are addressing, will focus on how we can use genomics to further categorize DCIS risk groups and identify patients who can safely avoid certain therapies because their recurrence risk is so low.”
Abstract
GS2-02: Impact of Tamoxifen Only after Breast Conservation Surgery for “Good Risk” Duct Carcinoma in Situ: Results from the NRG Oncology/RTOG 9804 and ECOG-ACRIN E5194 Trial. Jean Wright, University of North Carolina School of Medicine, Chapel Hill, North Carolina.
Presented at the San Antonio Breast Cancer Symposium, General Session 2, Dec. 12, 2024, 9 – 11:45 a.m. CT.
Authors and disclosures
A comprehensive listing of the study authors can be found on the conference website.
The study was supported by National Cancer Institute grants awarded to NRG Oncology and ECOG-ACRIN.
Wright declared no conflicts of interest.