Incidence Rates of Adverse Events (CTCAE Severity ≥3) During HER2-Directed Breast Cancer Treatment Assessing the Impact of App-Based Electronic Patient-Reported Outcomes in the Randomized Controlled PRO2 Trial

(1) Background: the evaluation of app-based ePROs is increasingly being used in clinical trials with cancer patients while a medical effect for patients is a matter of controversy; (2) Methods: in the randomized (1:1) controlled PRO2 trial the effect of the mediduxTM app on the rate of “high-grade AEs” (HAEs, CTCAE severity ≥3) within patients receiving HER2-directed breast cancer treatment (arm A) was compared to a control-group that did not use the app (arm B); (3) Results: Among patients with observed (non-imputed) HAE data (n = 180 of N = 189 in the ITT population), the rates of documented HAEs were 21.51% in arm B and 17.24% in arm A. Logistic regression of HAE incidence in the full ITT population (N = 189), using reference-based multiple imputation for missing values, showed a positive tendency towards app use, but no significant difference (odds ratio arm (A/B): 0.797, 95% CI: 0.363, 1.752; p-value 0.569). Also, AE-related secondary endpoints “emergency consultations” (risk ratio arm (A/B): 0.842, 95% CI: 0.464, 1.522; p-value 0.570) and “hospitalizations” (risk ratio arm (A/B): 0.575, 95% CI: 0.237, 1.329; p-value 0.201) had no significant differences in negative binomial regression. (4) Conclusions: Although the effect on HAE rates was not statistically significant, intensive app use was observed and adverse events recorded by participants corresponded well with the known drug-side-effect-profiles. These exploratory findings suggest a potential supporting role of the app during out-patient cancer treatment, which needs confirmation in adequately powered studies.