Baseline 'Bother' Predicts Quitting Aromatase Inhibitors

Nick Mulcahy

December 14, 2011

December 14, 2011 (San Antonio, Texas) — How well a breast cancer patient feels at the start of aromatase inhibitor (AI) therapy predicts eventual discontinuation, according to a study presented here at the 34th Annual San Antonio Breast Cancer Symposium.

The common troublesome adverse effects of AIs include vasomotor and joint symptoms, and "adherence to long-term endocrine therapy is poor," explained senior author of the study, Paul Goss, MD, from the Massachusetts General Hospital Cancer Center in Boston.

He and his coinvestigators decided to take a closer look at the problem of AI discontinuation. They wondered whether there was any way to identify patients at risk of quitting early.

They used data from the National Cancer Institute of Canada Clinical Trials Group MA.17 trial to explore the issue. That trial involves 7500 postmenopausal, estrogen-receptor-positive, early breast cancer patients who were randomized to either anastrozole or exemestane for 5 years.

The patients had received the usual array of adjuvant treatments before starting AI therapy: radiation, chemotherapy, and other hormonal therapy.

About 600 women in the study self-reported the adverse events they experienced, which included an assessment of the degree of "bother" from previous adjuvant treatment at baseline.

Being bothered at baseline by adverse effects from previous treatments significantly foretold who would quit an AI later on (hazard ratio [HR] 1.29; P = .006), reported Dr. Goss.

The investigators provided additional details about the severity of bother and discontinuation.

The AI patients were divided into 2 groups on the basis of their self-reported baseline bother from previous radiation, chemotherapy, and other hormonal therapy. The women were stratified according to the degree they were bothered at baseline: 559 reported being bothered a little bit or not at all (low-bother group); and 98 reported being bothered somewhat, quite a bit, or very much (higher-bother group). At 50 months, about 50% of patients in the higher-bother group had discontinued AI therapy, as did about 30% of the low-bother group.

"Nonadherence is predicted by severity of baseline symptoms — not by symptoms that develop on treatment," summarized Patricia Ganz, MD, who served as discussant of the study. She is from the Jonsson Comprehensive Cancer Center of the University of California, Los Angeles.

The emergence of joint pain in the first 3 months was also a reason for quitting an AI, but it was not statistically significant (HR, 1.11; P = .107), said Dr. Goss.

Study Details

The primary objective of this study was to learn whether exemestane or anastrozole had worse patient-reported symptoms. There was 1 discordance between the 2 treatment groups: 30.5% of women in the anastrozole group had undergone previous chemotherapy, whereas only 24.8% of the exemestane group did. Otherwise, the 2 groups were very similar.

Dr. Goss reported that, at month 6 of treatment, treatment-related symptoms were the same for the 2 drugs.

The secondary objectives of the study were to examine the effect of treatment-related symptoms on health-related quality of life and to identify patients at risk of discontinuing AI therapy.

The investigators decided to use the FACT-ES (Functional Assessment of Cancer Therapy-Endocrine Symptoms) for patient-reported outcomes (physical, functional, social, and emotional well being, as well as cancer-specific concerns).

Predictably, they report that treatment-related symptoms "negatively affect" health-related quality of life (P < .001).

A multivariate analysis found that baseline bother from previous breast cancer treatments was the most significant predictor of AI discontinuation. The covariates included demographics, disease characteristics, and endocrine symptoms such as weight gain and night sweats.

The study was sponsored by National Cancer Institute of Canada. Dr. Goss and Dr. Ganz have disclosed no relevant financial relationships.

34th Annual San Antonio Breast Cancer Symposium (SABCS): Abstract S6-2. Presented December 8, 2011

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