Cost-utility of first-line dostarlimab plus carboplatin-paclitaxel compared with placebo for patients with pA/rEC: a partitioned survival analysis

Given the rising incidence of endometrial cancer in Saudi Arabia, the integration of high-cost therapeutics, such as dostarlimab (DSR), for primary advanced or recurrent (pA/rEC) disease necessitates rigorous economic appraisal. Therefore, this study aimed to evaluate the cost-utility of first-line dostarlimab plus carboplatin-paclitaxel (DSR + CP) versus placebo plus carboplatin-paclitaxel (PBO + CP) from the perspective of the Saudi healthcare payer. A partitioned survival model was constructed to simulate patient prognosis across three health states: progression-free disease, progressive disease, and death. The model parameters were derived from the clinical efficacy data of the RUBY trial and the local cost inputs. The primary outcome was the incremental cost-effectiveness ratio (ICER), the robustness of which was evaluated via comprehensive deterministic and probabilistic sensitivity analyses to characterize parameter uncertainty. For the overall pA/rEC population, the DSR + CP regimen yielded an incremental 1.55 quality-adjusted life-years (QALYs) at an additional cost of $144,716, resulting in an ICER of $93,244 per QALY. Cost-effectiveness was more favorable in the mismatch repair deficient (dMMR) subgroup (ICER: $82,754/QALY) than in the mismatch repair proficient (pMMR) cohort (ICER: $132,571/QALY). The ICER is the most sensitive to the acquisition cost of the DSR. At a willingness-to-pay threshold of $90,000/QALY, the probability of DSR + CP being cost-effective was 83.9% for the dMMR subgroup. This economic evaluation indicates that DSR + CP constitutes a cost-effective intervention for pA/rEC within the dMMR subpopulation. These findings provide strong evidence for a tailored reimbursement policy that effectively utilizes resources by connecting clinical benefits with economic value in the management of pA/rEC. Given the rising incidence of endometrial cancer and financial pressures on the Saudi healthcare system, this study provides crucial, locally-specific economic evidence to inform policy and reimbursement decisions for the high-cost drug dostarlimab. This analysis reveals that adding dostarlimab to chemotherapy is only cost-effective for a specific subgroup of endometrial cancer patients (dMMR) in Saudi Arabia. Therefore, the findings strongly recommend mandatory biomarker testing to select the right patients for this expensive treatment and suggest that significant price negotiations are necessary to make it a viable option.