Endocrine Therapy Initiation and Medical Oncologist Utilization Among Women Diagnosed with Ductal Carcinoma in Situ.

Background: Though randomized clinical trials have demonstrated a reduction in second breast events with endocrine therapy among women with ductal carcinoma in situ (DCIS), use of these therapies remains highly variable. The purpose of this study was to evaluate patient and treatment-related factors associated with endocrine therapy initiation and medical oncology specialty utilization after DCIS.

Materials And Methods: We identified women with a DCIS diagnosis during 2006-2010 in the North Carolina Central Cancer Registry with linked public and private insurance claims in the University of North Carolina Integrated Cancer Information Surveillance System data resource. Multivariable generalized linear regression models were used to estimate risk ratios (RR) and 95% confidence intervals (CI) for endocrine therapy initiation in the year following DCIS diagnosis.

Results: Among 2,090 women with a DCIS diagnosis, 37% initiated endocrine therapy. Initiation was less common among women aged 75+ at diagnosis (RR = 0.79; 95% CI: 0.64-0.97 vs. age 45-54) and women treated with breast-conserving surgery (BCS) who did not receive radiation (RR = 0.63; 95% CI: 0.50-0.78 vs. BCS plus radiation). Consultation with a medical oncologist was strongly associated with endocrine therapy initiation (RR = 1.40; 95% CI: 1.23-1.61). Women who saw a medical oncologist more often had private insurance, higher census tract-level income, hormone receptor positive disease, and treatment with BCS and radiation.

Conclusion: Treatment strategies for DCIS remain controversial. Our data suggest that endocrine therapy is more often used in addition to standard therapies such as BCS plus radiation, rather than as an alternative to radiation. 2017;22:535-541 IMPLICATIONS FOR PRACTICE: Randomized trials have demonstrated a reduction in second breast cancer events with use of endocrine therapy for ductal carcinoma in situ (DCIS). However, notable variation exists in the uptake of these therapies among DCIS patients. In this study, factors associated with endocrine therapy initiation in the year following a DCIS diagnosis included consultation with a medical oncologist and treatment with breast-conserving surgery with radiation. Our findings help to explain the wide variation in endocrine therapy initiation and suggest the need for clear guidelines in the treatment of DCIS.