Matthew Galsky, MD
The addition of the CTLA-4 inhibitor ipilimumab (Yervoy) to cisplatin and gemcitabine did not significantly improve overall survival (OS) for patients with metastatic urothelial cancer, according to findings from a phase II study presented at the 2016 GU Cancers Symposium.
In the single-arm study, which was the first to explore the combination of an immune checkpoint inhibitor with chemotherapy in urothelial cancer, the median OS was 14.6 months (95% CI, 10.5-18.6). The 1-year OS rate was 59%, which did not meet the primary endpoint of the study. The objective response rate (ORR) with the combination was 64%.
“Response rate and survival were similar to historical controls, and the primary endpoint was not met,” said lead investigator Matthew Galsky, MD, director of Genitourinary Medical Oncology at the Tisch Cancer Institute at Mount Sinai. “We set a high bar for the improvement in 1-year overall survival of 20% compared with historical controls. We felt that we would really need to see something robust to warrant moving this regimen forward."
In the phase II study, 36 patients with metastatic urothelial carcinoma received induction therapy for 2 cycles with gemcitabine and cisplatin followed by the doublet plus ipilimumab for 4 cycles. The primary endpoint of the study was the 1-year OS rate. To be significant, the lower bound of the 90% confidence interval needed to exceed 60%, which is equivalent to a 1-year OS rate of 80%. The secondary endpoints of the study focused on ORR, progression-free survival, and safety.
Across both stages of the study, gemcitabine was administered at 1000 mg/m2
on days 1 and 8 and cisplatin was given at 70 mg/m2
on day 1 of each 21-day cycle. Ipilimumab was administered at 10 mg/kg on day 1 of each cycle. Following treatment with the triplet, patients with stable disease or better went on to receive maintenance ipilimumab at 10 mg/kg every 3 months.
The median age of patients was 60 years and the majority were males (81%). The primary tumor site was the bladder (78%), with 20% having renal pelvic disease. Nearly a third of the patients (30%) had a Karnofsky performance status of 80% and 58% had visceral metastasis. Prior treatments included systemic chemotherapy (15%) and surgical removal of the primary tumor (53%).
Across the full study, the complete response (CR) rate was 14%. Overall, 17% of patients experienced an improvement in response with the addition of ipilimumab following induction therapy. There was 1 CR following induction therapy and 4 CRs with the addition of ipilimumab. “It’s unclear, of course, if this is related to ipilimumab or to additional chemotherapy,” noted Galsky.
The partial response rate was 50%, across both treatment phases. These responses were primarily achieved during induction therapy (53%), some of which converted to CRs. The stable disease rate was 31%. After the predefined 6 cycles of treatment, 15 patients had stable disease or better and were eligible for maintenance therapy.
Patients received a median of 5 cycles of gemcitabine plus cisplatin and 3 cycles of ipilimumab. Disease progression was the most common cause of treatment discontinuation.
At least 1 grade 3/4 adverse event (AE) was experienced by 72% of patients. Potentially immune-related grade 3/4 AEs included diarrhea (8%), colitis (6%), rash (6%), adrenal insufficiency (3%), hypopituitarism (3%), and hyperthyroidism (3%).
The most commonly occurring grade 3/4 AEs in the trial were neutropenia (36%), anemia (28%), thrombocytopenia (19%), and diarrhea (9%). The most frequently reported grade 1/2 AEs were fatigue (64%), nausea (64%), anemia (36%), diarrhea (36%), anorexia (31%), rash (28%), vomiting (28%), alopecia (28%), neuropathy (25%), and thrombocytopenia (25%).
“The majority of adverse events were grade 1 and 2 in severity. The majority of grade 3 and 4 events were hematologic. We did observe non-hematologic toxicities consistent with immune-mediated toxicity,” said Galsky. “Based on the character, severity, and frequency of the adverse events, the side effect profile was consistent with additive toxicity rather than synergistic toxicity.”
In an exploratory analysis of immune cells, a significant depletion was not seen in circulating regulatory T cells or myeloid-derived suppressor cells following induction chemotherapy. Additionally, induction therapy did not appear to impact CD4 and CD8 levels, based on peripheral blood measurements. After the addition of ipilimumab, there was an expected expansion in CD4 and CD8 cells, noted Galsky.
“We did see pharmacodynamic effects consistent with the mechanism of ipilimumab, despite administration of concurrent cytotoxic chemotherapy,” he said. “This does potentially bode well for upcoming trials combining cytotoxic chemotherapy with PD-1 and PD-L1 blockade.”