Real-world analysis of pembrolizumab utilization and characteristics of patients being prescribed treatment in early stage RCC.

480 Background: In the United States, adjuvant pembrolizumab was approved on November 17, 2021, for patients with RCC with intermediate-high (T2N0M0-G4, T3N0M0, any grade) or high risk (T4, any grade; N+, any T, any grade; and M1NED patients) of recurrence following nephrectomy. This study aims to assess adoption of adjuvant pembrolizumab in routine practice and demographic and clinical characteristics of post nephrectomy RCC patients who received this therapy. Methods: This retrospective study included adult patients with non-metastatic localized RCC who underwent nephrectomy between November 17, 2021, and December 31, 2022, and were seen in the U.S. Oncology Network. Patients were excluded if they were treated for other documented primary cancer diagnoses or enrolled in clinical trials. Descriptive analyses were conducted to evaluate demographic, clinical, and treatment characteristics overall, and for patients who received adjuvant pembrolizumab monotherapy and those who did not. Multivariate logistic regression was used to identify factors associated with adjuvant pembrolizumab use. Results: In total, 178 patients were included. The mean age was 62 years (SD 11.8), with a majority being male (66.3%, n=118), and a median follow-up of 7.9 months (Q1,Q3: 4.1,9.8). The majority had intermediate-high risk (n=86, 57.5%), clear cell (cc) RCC (n=147, 82.6%) and received adjuvant pembrolizumab monotherapy (n=118, 66.3%). Among those who received adjuvant pembrolizumab, 90.7% had ccRCC, 62.5% were intermediate-high risk (T2N0G4: 8 (55.1%), T3N0 All Grades: 53 (44.9%)), 27.5% were N+ with a median follow-up of 8.3 (Q1, Q3: 6.0, 10.1) months. Median time to the start of adjuvant pembrolizumab post nephrectomy was 1.6 months (Q1, Q3: 1.3,2.1). The median time to treatment discontinuation was 11.5 months (Q1, Q3: 9.0, 11.5) (the recommended duration of treatment for adjuvant pembrolizumab is: 12 months at 17 cycles at 200mg/ Q3W or 9 cycles at 400mg/Q6W). Multivariate analysis showed that patients with non ccRCC histology were 93% less likely (p-value: <0.0001) and those whose with first oncologist visit >=2 months post nephrectomy were 60% less likely (p-value:0.035) to receive adjuvant pembrolizumab treatment. Conclusions: This study demonstrated notable uptake of adjuvant pembrolizumab among post-nephrectomy RCC patients in this community setting following FDA approval. RCC histology and the timing of oncologist visits post nephrectomy were significant factors influencing the receipt of adjuvant pembrolizumab. Future research should focus on examining referral patterns, and identifying the drivers and barriers to treatment adoption, with the goal of developing strategies to enhance its integration. Additionally, future research may explore long-term outcomes and real-world effectiveness of adjuvant pembrolizumab.