DCIS Treatment Regional Variation Linked To Subsequent Receipt Of Mastectomy

Likelihood of breast preservation for women with second breast events is influenced by regional variation in treatment intensity for ductal carcinoma in situ

medwireNews: Intensity of treatment for ductal carcinoma in situ (DCIS) may inadvertently alter the likelihood of mastectomy in women who experience a subsequent breast event, suggests a US study of regional variation in the use of radiotherapy after breast-conserving surgery (BCS).

“Most people would agree that the quality of life for patients with breast cancer has improved with the feasibility of BCS”, the researchers write in JAMA Oncology.

“An unintended consequence of using radiotherapy for DCIS is the increased use of mastectomy downstream among women who may have opted to receive less aggressive treatment for their initial DCIS (ie, BCS alone)”, they believe. 

The team examined Surveillance, Epidemiology, and End Results (SEER) data for 2679 women diagnosed with DCIS between 1990 and 2011, and SEER–Medicare data for 757 women diagnosed with DCIS between 1991 and 2009, all of whom underwent BCS without radiotherapy. The patients subsequently experienced a second diagnosis of stage 0–III breast cancer.

Patients who resided in a health service area with high intensity of treatment for DCIS – defined as over 69% of patients treated by the service for DCIS receiving radiation – were significantly more likely to undergo mastectomy rather than BCS for a second event than those in a low-intensity region, where less than 57% of patients initially received radiotherapy for first DCIS.

The rate of mastectomy in SEER patients rose from 40.8% in the low intensity regions to 49.6% in the high intensity areas and the corresponding increase for the SEER–Medicare patients was 38.6% to 54.5%.

Thus, the adjusted odds ratio for mastectomy in high versus low intensity regions were 1.43 and 1.90 for patients in the SEER and the SEER–Medicare databases, respectively.

Women who reside in regions with high intensity of radiation use for DCIS were therefore more likely to undergo mastectomy for a second event than those in low-intensity regions regardless of whether they had previously undergone radiotherapy, explain lead author Rinaa Punglia, from Dana-Farber Cancer Institute in Boston, Massachusetts, and team.

The researchers acknowledge they did not have access to information on possible confounders, such as patient preference for treatment, availability of adequate breast tissue for a good cosmetic result or a full raft of clinical characteristics.

But they emphasize that the odds ratios for mastectomy in high- versus low-intensity regions in the SEER and SEER–Medicare groups were similar after propensity score matching, at 1.87 and 1.56.

“Physicians in regions of high use of radiotherapy may guide patients with DCIS toward mastectomy because many of these patients are ineligible for BCS at the time of a second breast event—having already received radiotherapy—leading to mastectomy being recommended for patients who did not receive radiotherapy and are eligible for BCS”, they conclude.

“Awareness of this effect of practice patterns may be the first step toward its eradication and movement toward more patient-centered care.”

Reference

Punglia RS, Cronin AM, Uno H, et al. Association of regional intensity of ductal carcinoma in situ treatment with likelihood of breast preservation. JAMA Oncol 2016; Advance online publication 21 July. doi:10.1001/jamaoncol.2016.2164

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