Objective-To evaluate the effectiveness of methods that control for confounding by indication, we compared breast cancer recurrence rates among women receiving adjuvant chemotherapy versus those who did not.Study Design and Setting-In a medical record review-based study of breast cancer treatment in older women (n=1798) diagnosed 1990-1994, our crude analysis suggested adjuvant Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Conclusion-Conventional methods do not control for unmeasured factors, which often remain important when addressing confounding by indication. PS and IV analysis methods can be useful under specific situations, but neither method adequately controlled confounding by indication in this study. NIH Public AccessAuthor Manuscript J Clin Epidemiol. Author manuscript; available in PMC 2011 January 1.

Attention to nonadherence among older women at risk of discontinuation, particularly those receiving BCS without radiotherapy, might improve breast cancer outcomes for these women.