A Phase II Trial of Older Adults With Metastatic Breast Cancer Receiving nab‐Paclitaxel: Melding the Fields of Geriatrics and Oncology

Abstract

Micro‐Abstract nab‐Paclitaxel may be an attractive therapy for older adults because of its efficacy, the infrequency of allergic reactions, and the lack of need for steroid pre‐medications. We evaluated the tolerability and efficacy of nab‐paclitaxel in older adults with metastatic breast cancer, as well as the relationship between a geriatric assessment‐based toxicity risk score and chemotherapy toxicity, dose reductions, dose delays, and hospitalizations. Patients with intermediate/high toxicity risk scores had higher risk of grade ≥ 3 toxicity than those with low risk scores, and a higher mean risk score was associated with higher likelihood of dose reductions and hospitalizations. A geriatric assessment‐based risk score can help weigh the risks and benefits of chemotherapy in older adults, and should be incorporated into future trials testing new therapies in this population. Introduction: Phase II clinical trials including geriatric assessment (GA) measures are critical for improving the evidence base for older adults with cancer. We assessed the efficacy and tolerability of nab‐paclitaxel in older adults with metastatic breast cancer (MBC). Patients and Methods: Patients aged ≥ 65 years with MBC and ≤ 1 previous line of chemotherapy received 100 mg of nab‐paclitaxel on days 1, 8, and 15 of a 28‐day cycle. A GA was completed pre‐chemotherapy, and the validated Cancer and Aging Research Group (CARG) chemotherapy toxicity risk score was calculated. Relationships between tolerability (number of courses, hospitalizations, dose reductions, and toxicity) and risk score were assessed using general linear models, Student t tests, and the Fisher test. Response rate and progression‐free survival were evaluated using the Kaplan‐Meier method. Results: Forty patients (mean age, 73 years; range, 65‐87 years) were included. The median number of cycles was 6, 75% (n = 30) of patients had ≥ 1 dose hold, and 50% (n = 20) had ≥ 1 dose reduction. Fifty‐eight percent (n = 23) had treatment‐related ≥ grade 3 toxicities, and 30% (n = 12) were hospitalized owing to toxicity. Thirty‐five percent (n = 14) responded, and the median progression‐free survival was 6.5 months (95% confidence interval, 5.5 months to undefined). Patients with intermediate/high toxicity risk scores had higher risk of grade ≥ 3 toxicity than those with low risk scores (odds ratio, 5.8; 95% confidence interval, 1.3‐33.1; P = .01). A higher mean risk score was associated with higher likelihood of dose reductions and hospitalizations. Conclusions: Among older adults with MBC receiving weekly nab‐paclitaxel, more than one‐half experienced ≥ grade 3 chemotherapy toxicity. However, a GA‐based risk score could predict treatment tolerability.