Background: Pembro showed antitumor activity in 1L and 2L for pts with UC in the single-arm, phase 2 KEYNOTE-052 study (NCT02335424) and the randomized phase 3 KEYNOTE-045 (NCT02256436) study, respectively. This post hoc exploratory analysis evaluated whether primary tumor location affected efficacy and safety of pembro (KEYNOTE-052; KEYNOTE-045) and chemotherapy (chemo; KEYNOTE-045). Methods: KEYNOTE-052 enrolled cisplatin-ineligible pts with advanced/metastatic UC who had not previously received systemic therapy; they received pembro (200 mg IV Q3W). KEYNOTE-045 enrolled pts with advanced/metastatic UC who had received platinum-containing chemo; pts were randomly assigned 1:1 to receive pembro (200 mg IV Q3W) or investigator’s choice of chemo (paclitaxel, docetaxel, or vinflunine). Both studies required pts to have measurable disease per RECIST v1.1. Upper tract (UT) UC included primary tumors in the renal pelvis or ureter; lower tract (LT) UC included primary tumors in the bladder or urethra. Pts with UT and LT disease (UT/LT) were classified as LT. Pts receiving pembro were treated until disease progression, unacceptable toxicity, or withdrawal of consent, for up to 2y. End points were PFS, ORR, and DOR per RECIST v1.1 by central radiology assessment and OS. Results: A total of 369 pembro-treated pts (68 UT; 301 LT [79 UT/LT]) from KEYNOTE-052 plus 270 pembro-treated pts (93 UT; 177 LT [33 UT/LT]) and 272 chemo-treated pts (94 UT; 178 LT) from KEYNOTE-045 were evaluated. Median follow-up from randomization to data cutoff (09/26/20 and 10/1/20, respectively) was ≥56 mo. Both studies enrolled a similar percentage of pts with PD-L1–positive tumors (25%-30%). PFS, ORR, DOR, and OS for pembro were consistent regardless of tumor location, although ORR for KEYNOTE-045 was lower for the UT group (Table). In the chemo arm of KEYNOTE-045, similar efficacy was observed regardless of tumor location or regimen. Grade 3-5 TRAEs occurred at similar rates in KEYNOTE-052 (19.1% UT; 21.6% LT) and KEYNOTE-045 (17.2% UT; 16.8% LT). Conclusions: In this exploratory analysis, pembro showed similar clinical activity and manageable safety regardless of primary UC tumor location. Clinical trial information: NCT02256436 and NCT02335424.

^a+ indicates no progressive disease by the time of last disease assessment.