Forgetfulness A Significant Barrier to Oral Adherence in Elderly Patients With Prostate Cancer

Elderly patients with advanced prostate cancer who were prescribed enzalutamide (Xtandi) reported better adherence to oral treatment than those who were prescribed abiraterone, according to findings from a prospective trial of the Meet-URO network. However, the results, which were recently presented during the 2022 ASCO meeting, showed that forgetfulness is a potential barrier to adherence with this treatment.

Non-adherence rates were assessed by comparing the number of missed pills to the number of prescribed pills though pill counting, an overall estimate was given based on the median of individual values. The percentage of missed pills per prescribed pills was 5.2% in the abiraterone cohort compared with 4.2% in the enzalutamide cohort (P < .001). However, patients receiving enzalutamide were more likely to cite forgetfulness as their reason for non-adherence than their peers in the other cohort; the percentage of patients who cited forgetfulness as their reason was 42% (38 patients) vs 17% (4 patients), respectively (P < .001).

“Physicians tend to treat elderly and frailer [patients with] mCRPC with enzalutamide,” wrote study authors in the poster. “These [patients tend to be] more adherent to treatment, however, forgetfulness is a potential barrier.”

“Despite this, [abiraterone] conferred a longer progression-free survival [PFS] in our study population,” they wrote.

Radiographic PFS (rPFS) was defined from the time of treatment initiation until the date of disease progression, as per RECIST 1.1, or death of any cause. OS was measured from the date of treatment until death or last follow-up.

The median OS in the study was 48.8 months (36.8-60.8; P = .327). Notably, in the abiraterone cohort, the median OS was 48.8 months (95% CI, 34.3-63.3) compared with 42.3 months (95% CI, 39.1-45.4) in the enzalutamide group. The median rPFS in the whole study was 26.0 months (95% CI, 22.8-29.3; P = .041); in the abiraterone it was 28.4 months (95% CI, 24.2-32.5) and in the enzalutamide arm it was 23.1 months (95% CI, 18.2-28.1). Non-adherence was not linked to median OS or rPFS rates in either arm.

Novel-androgen hormonal therapies (NAHTs) for advanced prostate cancer are mainly oral treatments with manageable toxicity profiles, wrote study authors in the poster. Furthermore, the oral option allows the convenience of at-home administration and reduced hospital traffic.

One limitation of oral therapies, however, is the potential for non-adherence—for a variety of reasons. These treatments are self-administered, typically without supervision, by patients already overwhelmed by the assumption of many other concomitant medications. For elderly patients with advanced cancer, the challenge of adherence is an even more prominent social and health issue.

In this prospective observational cohort study, investigators assessed the treatment adherence of patients who were 70 years or older and who were diagnosed with metastatic castration resistance prostate cancer (mCRPC). These patients received either abiraterone (n = 86) or enzalutamide (n = 148), and their adherence was monitored via pill counting, a self-assessment questionnaire, and clinical diaries to be shared at each clinical visit.

A total of 234 patients from 6 different cancer centers were evaluated through the meet-URO-network. The median age was 78 years (range, 73-82). Sixty-nine percent of patients received NAHT in the pre-chemotherapy setting, 24% received NAHT post-chemotherapy, and 2% of patients received both concurrently.

Patients were monitored for adherence across a median of 7 cycles. The 2 cohorts were well balanced in terms of baseline characterize, except for in steroids use (100% v 9%; P < .001), since abiraterone requires steroids, and Charlson score, which was higher in patients receiving enzalutamide (range 10-12 vs 8-11, P = .028).

Investigators sought to better understand the autonomy and background of participating patients through the geriatric G8 questionnaire, age-adjusted Charlson Comorbidity Index, and Instrumental activities of daily living assessments. In addition, a short caregiver evaluation was collected. This assessment queried about presence, age, degree of kinship, working status, and caregiver qualifications.

A Wilcoxin 2-sample test was used to compare continuous variables, and a two-tailed Fisher exact test was used for the statistical comparison of proportions. The spearman correlation coefficient was used to explore the correlation between adherence behavior and potential clinical variables; the unsupervised median of individual non-adherence served as cut-off.

In the whole period of observation, the Geriatric G8 score (P = .004, R = 40.19), IADL, presence of caregivers (P = .03, R = .19, assumption of concomitant medication (P = .004, R = .013), and G12 toxicities (P = .02, R = .16) all demonstrated correlation to non-adherence in accordance with Spearman rank correlation coefficient. Despite this, after adjustments for Bonferroni correction, the Geriatric G8 score proved to be the only factor significantly associated with non-adherence.

The second most common reason for a patient to not take their medicine was because they felt like they “did not need it.” This reason was cited by 22 patients (24%) in the enzalutamide arm and 8 patients (35%) in the abiraterone arm, respectively (P < .001). Other cited reasons for non-adherence included “quantity” and “other.”

Reference

Rescigno P, Maruzzo M, Rebuzzi SE, et al. Adherence to oral treatments in elderly advanced prostate cancer patients, the ADHERE study: a prospective trial of the MEET-URO network.J Clin Oncol. 2022;40(suppl 16):12044. doi: 10.1200/JCO.2022.40.16_suppl.12044