Currently submitted to: JMIR Research Protocols
Date Submitted: Feb 7, 2020
(currently open for review)
The Effects of Radiotherapy and Comorbidity on Health-Related Quality Of Life and Mortality among Older Women with Low-Risk Breast Cancer: Proposal For a Retrospective Longitudinal Study
The National Comprehensive Cancer Network Breast Cancer Guidelines Committee has suggested that the omission of adjuvant radiation therapy (RT) after breast-conserving surgery can be a reasonable option among older women with low-risk breast cancer (early-stage, ER-positive, and node-negative) if they are treated with endocrine therapy. However, RT usage in this group of women still exceeds 50%. On the other hand, older women tend to forego RT (even when necessary) due to cost, inconvenience, and potential adverse responses associated with RT. Understanding health-related quality of life (HRQOL) change with receipt of RT among older women in the modern era is limited due to the underrepresentation of this population in clinical trials.
The proposed study aims to examine the associations of RT with HRQOL trajectories as well as survival outcomes among older women over 5-10 year follow-up. We will also assess whether pre-diagnosis comorbidity burden influences receipt of RT and whether the associations between RT and HRQOL trajectory and survival outcomes are modified by comorbidity burden.
We will use a retrospective cohort study design with the population-based database of Surveillance, Epidemiology, and End-Results linked to the Medicare Health Outcomes Survey (SEER-MHOS). Older women (65+) diagnosed with low-risk breast cancer in 1998-2014, received BCS, and participated in MHOS 1998-2016 are eligible for the current analysis. The clustering method, latent class analysis, will be used to identify each patient’s pre-diagnosis comorbidity burden, and HRQOL will be evaluated using SF-36/VR-12 scales. The inverse-weighted estimates of the probability of treatment will be included as a covariate to control for treatment selection bias and confounding effects in subsequent analysis. The association of RT with HRQOL trajectory will be evaluated using inverse-weighted semiparametric B-splines models. The inverse-weighted Cox regression model will be used to obtain hazard ratios with 95% confidence intervals for the association of RT with survival outcomes. Differential effects of RT on both outcomes according to comorbidity burden class will also be evaluated.
As of January 2020, the study was approved by the institutional review board, and the SEER-MHOS data was obtained from the National Cancer Institute and SEER. Women with low-risk breast cancer who met inclusion and exclusion criteria have been identified, and pre-diagnosis comorbidity burden has been characterized using latent class analysis. Further data analysis will begin in February 2020, and the first manuscript will be submitted in a peer-reviewed journal in June 2020.
This research has the potential to improve clinical outcomes of older women with low-risk breast cancer by providing them additional information on the HRQOL trajectories when they make RT treatment-decision. It will facilitate informed, shared treatment decision and cancer care planning and ultimately will improve the HRQOL of older women with breast cancer. Clinical Trial: NA
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