Purpose: Aromatase Inhibitor-Associated Musculoskeletal Symptoms (AIMSS) are common and frequently lead to AI discontinuation. Single nucleotide polymorphisms (SNPs) in candidate genes have been associated with AIMSS and AI discontinuation. E1Z11 is a prospective cohort study designed to validate associations between 10 SNPs and AI discontinuation due to AIMSS.
Patients and methods: Postmenopausal women with stage I-III hormone receptor-positive breast cancer received anastrozole 1 mg daily and completed patient-reported outcomes (PRO) to assess AIMSS (Stanford Health Assessment Questionnaire; HAQ) at baseline, 3, 6, 9, and 12 months. We estimated that 40% of participants would develop AIMSS, and 25% would discontinue AI treatment within 12 months. Enrollment of 1,000 women with a fixed number per racial strata provided 80% power to detect an effect size of 1.5-4. SNPs were in ESR1 (rs2234693, rs2347868, rs9340835), CYP19A1 (rs1062033, rs4646), TCL1A (rs11849538, rs2369049, rs7158782, rs7159713), and HTR2A (rs2296972).
Results: Of 970 evaluable women, 43% developed AIMSS and 12% discontinued AI therapy within 12 months. While more Black and Asian women developed AIMSS compared to White women (49% vs 39%, p=0.017; 50% vs 39%, p=0.004, respectively), AI discontinuation rates were similar across groups. None of the SNPs were significantly associated with AIMSS or AI discontinuation in the overall population, or in distinct cohorts. The odds ratio for rs2296972 (HTR2A) approached significance for developing AIMSS.
Conclusion: We were unable to prospectively validate candidate SNPs previously associated with AI discontinuation due to AIMSS. Future analyses will explore additional genetic markers, PRO predictors of AIMSS, and differences by race.