Originally published as JCO Early Release 10.1200/JCO.2006.10.1022 on December 10 2007

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Predictors of Tamoxifen Discontinuation Among Older Women With Estrogen Receptor–Positive Breast Cancer

Cynthia Owusu, Diana S.M. Buist, Terry S. Field, Timothy L. Lash, Soe Soe Thwin, Ann M. Geiger, Virginia P. Quinn, Floyd Frost, Marianne Prout, Marianne Ulcickas Yood, Feifei Wei, Rebecca A. Silliman

From the Division of Hematology/Oncology, University Hospitals of Cleveland, Cleveland, OH; Group Health Center for Health Studies, Seattle, WA; Meyers Primary Care Institute: Fallon Community Health Plan/Fallon Foundation/University of Massachusetts Medical School, Worcester; Boston University Medical Center, Boston, MA; Division of Public Health Sciences, Department of Social Sciences and Health Policy, Wake Forest University School of Medicine, Winston-Salem, NC; Department of Research and Evaluation, Kaiser Permanente Medical Care Program, Pasadena, CA; Lovelace Respiratory Research Institute, Albuquerque, NM; Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT; Josephine Ford Cancer Center, Henry Ford Health System, Detroit, MI; and HealthPartners Research Foundation, Minneapolis, MN

Corresponding author: Cynthia Owusu, MD, MSc, Case Western Reserve University, University Hospitals Health System Ireland Cancer Center-BHC 5055, 11100 Euclid Ave, Cleveland, OH 44106-5055; e-mail: cynthia.owusu{at}case.edu

Purpose: Five years of adjuvant tamoxifen therapy for estrogen receptor (ER) –positive breast cancer is more effective than 2 years of use. However, information on tamoxifen discontinuation is scanty. We sought to identify predictors of tamoxifen discontinuation among older women with breast cancer.

Patients and Methods: Within six health care delivery systems, we identified women 65 years old diagnosed with stage I to IIB ER-positive or indeterminant breast cancer between 1990 and 1994 who had filled a prescription for adjuvant tamoxifen. We observed them for 5 years after initial tamoxifen prescription. We used automated pharmacy records to validate tamoxifen prescription information abstracted from medical records. The primary end point was tamoxifen discontinuation, operationalized as ever discontinuing tamoxifen during 5 years of follow-up. We used Cox proportional hazards to identify predictors of tamoxifen discontinuation.

Results: Of 961 women who were prescribed tamoxifen, 49% discontinued tamoxifen before the completion of 5 years. Discontinuers were more likely to be aged 75 to less than 80 years (v < 70 years; hazard ratio [HR] = 1.41; 95% CI, 1.06 to 1.87), be aged 80 years (HR = 2.02; 95% CI, 1.53 to 2.66), have an increase in Charlson Comorbidity Index at 3 years from diagnosis (HR = 1.52; 95% CI, 1.18 to 1.95), have an increase in the number of cardiopulmonary comorbidities at 3 years (HR = 1.75; 95% CI, 1.34 to 2.28), have indeterminant ER status (v ER-positive status; HR = 1.36; 95% CI, 1.00 to 1.85), and have received breast-conserving surgery (BCS) without radiotherapy (v mastectomy; HR = 1.62; 95% CI, 1.18 to 2.22).

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

published online ahead of print at www.jco.org on December 10, 2007.

Supported by Grant Nos. K05 CA92395, CA093772, and CA093772-04S1 from the National Cancer Institute and by an American Society of Clinical Oncology Foundation Young Investigator Award.

Presented in part at the 42nd Annual Meeting of the American Society of Clinical Oncology, June 2-6, 2006, Atlanta, GA.

Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article.

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