Abstract
The mainstay of treatment for ductal carcinoma in situ (dcis) involves surgery in the form of mastectomy or lumpectomy. Inconsistency in the use of endocrine therapy (et) for dcis is evident worldwide. We sought to assess the variation in et prescribing for patients with dcis across a population-based radiotherapy (rt) program and to identify variables that predict its use. Data from a breast cancer database were obtained for women diagnosed with dcis in British Columbia from 2009 to 2014. Associations between et use and patient characteristics were assessed by chi-square test and multilevel multivariate logistic regression. The Kaplan-Meier method, with propensity score matching and Cox regression analysis, was used to assess the effects of et on overall survival (os) and relapse-free survival (rfs). For the 2336 dcis patients included in the study, et use was 13% in dcis patients overall, and 17% in patients with estrogen receptor-positive (er+) tumours treated with breast-conserving surgery and rt. Significant variation in et use by treatment centre was observed (range: 8%-23%; p < 0.001), and prescription of et by individual oncologists varied in the range 0%-40%. After controlling for confounding factors, age less than 50 years [odds ratio (or): 1.72; p = 0.01], treatment centre, er+ status (or: 5.33; p < 0.001), and rt use (or: 1.77; p < 0.001) were significant predictors of et use. No difference in os or rfs with the use of et was observed. In this population-based analysis, 13% of patients with dcis in British Columbia received et, with variation by treatment centre (8%-23%) and individual oncologist (0%-40%). Age less than 50 years, er+ status, and rt use were most associated with et use.
Highlights
Ductal carcinoma in situ is a type of pre-invasive breast cancer in which the cancerous cells are confined to the epithelial lining of milk ducts in breast tissue[1]
For the 2336 dcis patients included in the study, et use was 13% in dcis patients overall, and 17% in patients with estrogen receptor–positive tumours treated with breast-conserving surgery and rt
Significant variation in et use by treatment centre was observed, and prescription of et by individual oncologists varied in the range 0%–40%
Summary
Ductal carcinoma in situ (dcis) is a type of pre-invasive breast cancer in which the cancerous cells are confined to the epithelial lining of milk ducts in breast tissue[1]. That approach has been supplanted with increased use of breast-conserving surgery (bcs), involving lumpectomy followed by radiotherapy (rt) to achieve similar outcomes, albeit with a slightly higher risk of recurrence[4,5]. A meta-analysis of two randomized clinical trials investigating the use of tamoxifen in dcis reported that, compared with placebo, tamoxifen given after lumpectomy (with or without rt) lowered the risk of recurrent ipsilateral and contralateral dcis, without improvement in all-cause mortality[6]. A subsequent retrospective analysis of the National Surgical Adjuvant Breast and Bowel Project (nsabp) B-24 trial found that the risk of developing breast cancer was halved when women with estrogen receptor–positive (er+) tumours received tamoxifen (compared with placebo); no benefit was noted for er-negative tumours[7]. Endocrine therapy (such as tamoxifen) is associated with many side effects, including increased risk for thromboembolic events and uterine cancer, necessitating discussion between physicians and their patients about the risks and benefits of the therapy[5,8]
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