Geriatric assessment played a central role in identifying patients with metastatic castrate-resistant prostate cancer (mCRPC) who are less likely to adhere to oral antiandrogen therapy with enzalutamide or abiraterone, according to study findings reported in Supportive Care in Cancer.1
As use of oral antiandrogen agents (enzalutamide and abiraterone) becomes more common in the setting of prostate cancer, the risk of nonadherence to these treatments also has the potential to increase, particularly for older patients.
Nevertheless, the study authors noted that “no compelling evidence is still available on adherence to abiraterone or enzalutamide for the treatment of mCRPC.”
This observational prospective cohort study enrolled 58 patients with mCRPC receiving oral antiandrogen therapy with enzalutamide (62%) or abiraterone (38%) at a single hospital in Italy. Adherence to oral antiandrogen agents was assessed using a pill counting method conducted at each monthly appointment. In addition, self-assessments of adherence to these oral therapies were implemented for some patients (n=42) during the study. These included a modified version of the self-assessment Basel Assessment of Adherence Scale (BAAS), as well as patient clinical diaries, that were conducted/reviewed at clinical visits every 28 days.
Clinical characteristics of the patient cohort included a median age of 76 years, and a median age-adjusted Charlson comorbidity score of 10. The median geriatric G8 score obtained using the G8 screening tool to identify patients most likely to benefit from a comprehensive geriatric assessment (G8 score of 14 or lower) was 14.2,3 More than half of patients were taking more than 3 drugs, and nearly three-quarters of patients had not received chemotherapy prior to treatment with abiraterone or enzalutamide. Most patients (81%) had a caregiver.
Using the pill counting method to assess adherence, nonadherence rates of 4.8% and 6.2% were determined for the overall study period of 12 months and the first 3 months of the study, respectively. However, patient self-assessment by the BAAS tool revealed a medication nonadherence rate of only 1.3% for the overall study period, with “misperception of the need of the drug” and “forgetfulness” reported as the most common reasons for medication nonadherence. Rates of diary nonadherence were high: 38% for the overall study period and 36% during the first 3 months of the study.
Discrepancies between medication nonadherence rates assessed through pill counting and patient reports “suggest that the patient tends to underestimate nonadherence and/or that the self-assessed BAAS questionnaire probably cannot be considered a suitable tool in this setting,” the study authors concluded.
Of note, on multivariate analysis, the geriatric G8 score (P =.005) was significantly associated with medication nonadherence for the overall study period.
“This supports the importance of the identification of frail patients, even with an easy-to-use and quick screening tool as the G8 is, and that specific interventions should be directed to patients with a G8 score of ≤14,” the study authors commented.
In addition, a significant association between low radiological response and medication nonadherence was observed (P =.03), leading the study authors to note that an awareness of the benefit of oral antiandrogen therapy may increase patient motivation to regularly take the drug.
They further proposed that patient frailty and low radiological response may reflect a cause and a consequence, respectively, of patient nonadherence to abiraterone and enzalutamide.
In their concluding remarks, the study authors stressed the importance of “geriatric assessment and clinical interventions to monitor and increase [patient] adherence [to these medications].”
1. Banna GL, Urzia V, Benanti C, et al. Adherence to abiraterone or enzalutamide in elderly metastatic castration-resistant prostate cancer [published online January 20, 2020]. Support Care Cancer. doi: 10.1007/s00520-020-05311-5
2. Bellera CA, Rainfray M, Mathoulin-Pélissier S, et al. Screening older cancer patients: first evaluation of the G-8 Geriatric Screening Tool. Ann Oncol. 2012;23(8):2166-2172.
3. International Society of Geriatric Oncology. Comprehensive Geriatric Assessment (CGA) of the older patient with cancer. https://www.siog.org/content/comprehensive-geriatric-assessment-cga-older-patient-cancer. Accessed February 6, 2020.