Improving Medication Adherence With Adjuvant Aromatase Inhibitor in Women With Breast Cancer: A Randomised Controlled Trial to Evaluate the Effect of Short Message Service (SMS) Reminder

This study is a prospective randomised controlled parallel trial of SMS reminder versus standard care to investigate whether SMS reminder improves adherence to oral aromatase inhibitor (AI) therapy amongst women with breast cancer at 1-year follow-up.

All subjects will be randomised to receive either SMS reminder or standard care in a 1:1 ratio. Balanced permuted block randomisation will be implemented with random varying of block sizes of 4 or 6.

The sample size is estimated based on the primary endpoint of medication adherence (as measured via SMAQ) at 1-year. Assuming that the proportion of medication adherence in the intervention and control groups are 80% and 60% respectively, then based on a 5% significance level and a power of 90%, a minimum sample of 240 subjects (i.e. 120 per group) will be required. Further assuming an attrition rate of 10%, the anticipated trial size is 280 overall.

The assessment of medication adherence at 1-year (as measured via SMAQ) between the SMS reminder and control groups will be made using chi-square test. Adjustment for baseline covariate and potential confounders will be made using the logistic regression where appropriate.

Other measures of adherence such as the 1-year MPR, PDC and pill count will be compared between treatment arms via the t- test, with adjustment for confounders made via the analysis of covariance (ANCOVA).