Pentoxifylline and vitamin E drug compliance after adjuvant breast radiation therapy

PURPOSE: Breast fibrosis is a common late effect after therapeutic irradiation that can result in pain, poor cosmesis, and functional impairment. Randomized trials have demonstrated that radiation fibrosis may be preventable with a medication regimen of pentoxifylline and vitamin E. This study investigates patient compliance with pentoxifylline therapy while examining possible correlations to compliance. METHODS AND MATERIALS: We identified 90 patients who were prescribed pentoxifylline (400 mg 3 times daily) and vitamin E (400 IU once daily) after adjuvant breast radiation. A retrospective cohort study was conducted using medical record analysis. Data were collected, including patient age, comorbid conditions, concurrent medications, duration of pentoxifylline and vitamin E therapy, dose adjustments, patient-reported side effects, and cause for discontinuation. A multivariate analysis of the correlation between medication compliance and these categorical variables was assessed with a χ(2) analysis of independence. RESULTS: Patient compliance with pentoxifylline and vitamin E therapy was found to be poor in 33 of 87 patients (38%) in the cohort, necessitating either dose reductions or discontinuation of therapy. There was a statistically significant correlation between concurrent antiemetic therapy and successful completion of pentoxifylline regimen. Of those on antiemetic therapy, 89% completed pentoxifylline as prescribed versus 48% of those without antiemetics (P < .001). There was a statistically significant correlation between concurrent proton pump inhibitor (PPI) therapy and discontinuation of pentoxifylline. Of those on PPI therapy, 33% completed pentoxifylline versus 81% of those not on PPIs (P < .001). All other variables examined were not significantly correlated with compliance. CONCLUSIONS: Patient compliance with pentoxifylline appears to be worse in clinical practice compared with previously published studies. Nausea was the most frequently reported indication for treatment modification or discontinuation. Concurrent antiemetic therapy was correlated with strong regimen compliance, but concurrent PPI therapy was correlated with poor compliance, independent of comorbid conditions.