Accepted for/Published in: JMIR Formative Research
Date Submitted: May 12, 2026
Date Accepted: Aug 26, 2026
When the Bottle Talks Back: A Post-hoc Exploratory Analysis of Health Literacy and Capecitabine Adherence in a Randomized Controlled Pilot Trial of Remote Monitoring for Breast Cancer
ABSTRACT
Background:
Oral anticancer therapy enables convenient, home-based cancer care but can introduce adherence challenges, particularly for regimens with complex dosing schedules. Capecitabine is an oral fluoropyrimidine commonly used in breast cancer and other solid tumors, often as adjuvant therapy or in advanced disease, and typically requires twice daily dosing on cyclical schedules, increasing the risk of missed or incorrect doses. Low health literacy may exacerbate these difficulties, and emerging remote monitoring tools may help close this gap.
Objective:
We evaluated whether health literacy was associated with adherence to capecitabine, and if health literacy modified the effectiveness of a remote monitoring intervention.
Methods:
Post-hoc analyses of a 2-arm pilot trial randomizing women with breast cancer prescribed capecitabine to enhanced usual care (EUC) or remote patient monitoring (RPM). Adherence was captured with a smart connected pill bottle that recorded dose timing and quantity. RPM participants received messages for missed or incorrect doses and weekly symptom assessments. Incorrect/missed doses and severe symptoms triggered alerts to the oncology team. Health literacy was captured at enrollment. To evaluate moderation, we used multivariate linear regression with an interaction term (health literacy × intervention arm) predicting adherence (proportion of days). Marginal effects quantified differences in adherence by study arm and health literacy.
Results:
Among 28 participants, 32.1% (n=9) had lower health literacy, 57.1% were Black, 35.7% White, and 53.6% had income below 200% of the federal poverty level. Among participants with lower health literacy, the RPM intervention was associated with higher adherence than EUC (87.5% vs 65.5%; adjusted difference, +22.1 percentage points, 95% CI: 6.2 to 37.9; P=.008). Among participants with higher health literacy, adherence did not differ significantly by arm (89.9% RPM vs 84.1% EUC; adjusted difference, +5.7 percentage points; 95% CI, -5.2 to 16.7; P=.29). Among those in EUC, lower health literacy was associated with significantly lower adherence (65.5% vs. 84.1%; adjusted difference: –18.6 percentage points; 95% CI: –32.4 to –4.9; P=.01). Among RPM participants, adherence did not differ by health literacy level (87.5% vs. 89.9%; adjusted difference: –2.3 percentage points; 95% CI: –15.8 to 11.1; P=.73).
Conclusions:
In this small pilot trial, a remote monitoring intervention was associated with higher capecitabine adherence among participants with lower health literacy, suggesting that health literacy–related adherence barriers may be addressable with remote monitoring support. Larger, prospectively powered studies should confirm these findings and evaluate downstream clinical outcomes. Clinical Trial: Clinical Trial Registration: NCT05086731 Registration date: 10/19/2021
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