Background: In the phase III GALLIUM study, obinutuzumab (GA101; G) plus chemotherapy (G+chemo) demonstrated superior progression-free survival (PFS) compared with rituximab (R) plus chemotherapy (R+chemo) for first-line treatment of patients with follicular lymphoma (FL) (Marcus et al., New Engl J Med 2017). G+chemo was subsequently shown to be highly cost effective vs. R+chemo, with a cost per quality-adjusted life year (QALY) of $2,300. Two R biosimilars, rituximab-abbs (Ra) and rituximab-pvvr (Rp), have now been FDA approved in this setting. The cost effectiveness of G+chemo vs Ra+chemo and Rp+chemo has not yet been estimated.

Methods: We adapted an existing Markov model comparing G+chemo vs. R+chemo, utilizing the GALLIUM trial's investigator-assessed PFS and post-progression survival to model overall survival. We assumed efficacy and safety equivalence for R biosimilars plus chemo and the R+chemo arm. Drug utilization, treatment duration, and adverse events (AEs) were based on GALLIUM trial data as of April 2018. Patients were randomized to either R+chemo or G+chemo; responders at end of induction received G or R maintenance for 2 yrs. We included costs for drugs, AEs, drug administration, and follow-up treatment upon disease progression. Health care costs were based on Medicare reimbursements; drug costs were April 2020 average sale prices for intravenous therapies or wholesale acquisition costs for oral therapies used post-progression; both R biosimilars cost less than R, and Rp cost less than Ra. Utility estimates were based on GALLIUM trial data and published literature and were used to estimate QALYs. Sensitivity analyses assessed key drivers of the model and uncertainty in the results.

Results: Treatment with G+chemo led to an increase in QALYs relative to R biosimilars+chemo of 0.93 (95% credible range [CR] 0.37–1.50). The total cost of G+chemo was $196,800, while those of Ra+chemo and Rp+chemo were $190,000 and $178,800, respectively, resulting in incremental costs of $6,800 (95% CR: -$1,200–$14,000) and $18,100 (95% CR: $10,700–$25,400), respectively. The average total cost was greater for G+chemo, primarily due to increased drug and administration costs ($128,100 for G+chemo vs. $114,600 for Ra+chemo and $103,400 for Rp+chemo); however, this was largely offset by cost savings for disease progression of -$7,800. AE costs were higher for G+chemo ($5,700) vs. R biosimilars+chemo ($4,400). The incremental cost-effectiveness ratios were $7,300 and $19,400 per QALY gained for G+chemo vs Ra+chemo and Rp+chemo, respectively. In probabilistic sensitivity analyses, G+chemo was cost effective at the $50,000 and $100,000 per QALY thresholds vs. both Ra+chemo (99% and 100% probabilities of cost effectiveness, respectively) and Rp+chemo (94% and 99%, respectively).

Conclusions: Despite the lower cost of R biosimilars compared with R, G+chemo is likely cost effective in the US as first-line treatment for FL, driven by delaying expensive progression treatments and increasing QALYs.

Citation Format: David L. Veenstra, Gregory F. Guzauskas, Scott J. Spencer, Federico Felizzi, Aino Launonen, Keith Dawson, Anthony Masaquel. Obinutuzumab plus chemotherapy is cost effective versus rituximab biosimilars plus chemotherapy for previously untreated follicular lymphoma patients [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr PO-58.