Idelalisib is a chemotherapy drug that is used to treat certain blood cancers. It is routinely used as a monotherapy in relapsed follicular lymphoma (FL) and as a combination therapy with rituximab for relapsed chronic lymphocytic leukemia (CLL). However, the toxic effects of idelalisib can be severe. This study aims to investigate idelalisib treatment outcomes.

This cohort study included a total of 26 trial participants aged 65 years or old who were treated with idelalisib for relapsed FL, along with 305 medicare beneficiaries treated with idelalisib of the same disease state and treatment regimen. Similarly, 89 participants and 294 beneficiaries who were given idelalisib with rituximab for relapsed CLL. The primary outcomes of the study were treatment duration, mortality, and treatment-related adverse outcomes.

The Medicare beneficiaries in both groups were older with higher comorbidity. The beneficiaries had a shorter median treatment duration for CLL compared with trial participants (173 vs. 473), though this trend was not seen in the FL group (114 vs. 160). Higher mortality and fatal infection rates were also observed in beneficiaries, as compared with trial participants.

The research concluded that there were significant imbalances in treatment outcomes and baseline comorbidities between trial participants and Medicare beneficiaries.