Idelalisib May Induce More Favorable Outcomes in Clinical Trial Participants, Versus Medicare Beneficiaries

A recent comparison study published in JAMA Oncology found Medicare beneficiaries aged 65 or older being treated with idelalisib (Zydelig) were older, sicker, and had more unfavorable treatment durations, mortality rates, and infections compared to participants of clinical trials.¹

This study, which focused on patients treated for follicular lymphoma and chronic lymphocytic leukemia (CLL), gathered a population of 115 clinical trial participants and 599 Medicare beneficiaries aged 65 or older treated with idelalisib. More specifically, 26 trial participants and 305 Medicare beneficiaries received idelalisib for follicular lymphoma, and 89 trial participants and 294 Medicare beneficiaries received idelalisib plus rituximab (Rituxan) for CLL.

“We observed substantial imbalances in baseline comorbidities and treatment outcomes between Medicare beneficiaries and trial participants aged 65 years or older,” the researchers wrote.

Among Medicare beneficiaries, the day-180 treatment discontinuation rate was 43.2% for those treated with idelalisib plus rituximab for CLL and 47.2% among patients with idelalisib for follicular lymphoma. Both numbers were considered high, especially compared to trial participants for idelalisib plus rituximab for CLL, which was only 18%. Even more, almost 2 times more trial participants received dose reductions compared to Medicare beneficiaries in both the combination arm (32.6% vs. 18.0%; P = .003) and the monotherapy arm (38.5% vs. 16.1%; P = .02).

As for mortality rates and fatal infections, Medicare beneficiaries had a higher overall mortality rate than trial participants for both idelalisib for follicular lymphoma (HR, 1.39; 95% CI, 0.69- 2.78) and idelalisib plus rituximab for CLL (HR, 1.40; 95% CI, 0.93- 2.11). Medicare beneficiaries also saw a higher fatal infection rate, most frequently pneumonia and sepsis, compared to trial participants in both idelalisib plus rituximab for CLL (18.4 vs 9.8, P = .04) and numerically in idelalisib for FL (27.6 vs 18.6, P = .54).

“Immunosuppression-related toxic effects, including infections, may have been somewhat reduced in trials by more frequent dose reductions and exclusion of patients with ongoing infections,” wrote Bird and colleagues. “Selective eligibility criteria and closer monitoring of trial patients may be responsible for limited generalizability of trial data to clinical practice.”

Trial eligibility criteria was a unique aspect of this study, as most other trials have a narrow population of lower-risk patients. Bird and colleagues believe this detail may be responsibility for the differences seen between Medicare beneficiaries and trial participants as it pertains to baseline comorbidity.

A limitation of the study was the inability for Bird and colleagues to accurately identify all causes of death in the study’s population. While this lack of complete data is significant, the researchers stressed that their focus was on serious infection within 30 days of participants’ death. Even more, while the study provided valuable information regarding Medicare beneficiaries with clinical trials, trial data gives more complete data regarding comorbidity and prior drug therapy.

“Our study findings also suggest a recent serious infection may represent a negative prognostic factor and warrant caution regarding idelalisib initiation in such patients,” wrote Bird and colleagues. “Compliance with [pneumocystis jirovecii pneumonia] prophylaxis and close monitoring of absolute neutrophil counts, with appropriate dose interruptions and reductions, may help reduce the rate of serious infections.”

Reference:

Bird ST, Tian F, Flowers N, et al. Idelalisib for Treatment of Relapsed Follicular Lymphoma and Chronic Lymphocytic Leukemia. JAMA Oncol. doi:10.1001/jamaoncol.2019.3994.