A longitudinal study of non-medical determinants of adherence to R-CHOP therapy for diffuse large B-cell lymphoma: implication for survival

Background: Adherence to therapy has been established for years as a critical parameter for clinical benefit in medical oncology. This study aimed to assess, in the current practice, the influence of the socio-demographical characteristics and the place of treatment on treatment adherence and overall survival among diffuse large B-cell lymphoma patients. Methods: We analysed data from 380 patients enrolled in a French multi-centre regional cohort, with diffuse large B-cell lymphoma receiving first-line treatment with R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) or R-CHOP-like regimens. Direct examination of administrative and medical records yielded the date of death. We studied the influence of patients' socio-demographic characteristics and place of treatment on the treatment adherence and overall survival, adjusted for baseline clinical characteristics. Treatment adherence was measured by the ratio between received and planned dose Intensity (DI), called relative DI (RDI) categorized in "lesser than 85%" and "at least 85%". Results: During the follow-up, among the final sample 70 patients had RDI lesser than 85% and 94 deceased. Multivariate models showed that advanced age, poor international prognosis index (IPI) and treatment with R-CHOP 14 favoured RDI lesser than 85%. The treatment in a public academic centre favoured RDI greater than or equal to 85%. Poor adherence to treatment was strongly associated with poor overall survival whereas being treated in private centres was linked to better overall survival, after adjusting for confounders. No socioeconomic gradient was found on both adherence to treatment and overall survival. Conclusions: These results reinforce adherence to treatment as a critical parameter for clinical benefit among diffuse large B-cell lymphoma patients under R-CHOP. The place of treatment, but not the socioeconomic status of these patients, impacted both RDI and overall survival.