Dr. Rosenberg, on behalf of the CheckMate investigators, presented longer-term 2-year data on the nivolumab-only arm of the study. The initial phase I/II report published in 2016 demonstrated a response rate (ORR) of 24% and 22% Grade 3-4 complications rate.
Now, at 2-years of follow-up, the ORR% is 25.6%. Importantly, the study now has information on PD-L1 tumor expression levels (<1% vs. >1%). 53% of patients in the study had low levels of PD-L1 expression. Interestingly, the ORR% did not differ between the groups -- ~26% ORR% in both low- and high-PD-L1 expression groups.
The median time to response is 2 months, and duration of response was not reached at 2-year follow-up. Amazingly, 65% of patients who initially responded are still enjoying a durable response at 2 years. Looking at Kaplan-Meier progression and survival curves, there appear to be very few progression events after 1 year of therapy. This is mirrored by the overall survival (OS) data as well. The 1yr-OS was 46% and 2-yr OS was 37%. The median OS was 10 months. These types of durable responses are extremely rare in chemotherapy-only studies!
With regard to treatment-related adverse events (AEs), investigators reported 83% for all grades, and 28% for Grade 3-4 AEs. Only 3.8% of AEs led to treatment discontinuation. There was one death due to pneumonitis on study.
In conclusion, there were no new safety signals or cause for concern with longer-term follow-up in the nivolumab-only arm of CheckMate 032. Responses remained around 25%, and those who respond tend to maintain that response by 2-year follow-up. These responses did not differ based on PD-L1 expression. These are extremely exciting data for patients with platinum-resistant metastatic UC. Follow-up from the nivolumab + ipilimumab arms are eagerly anticipated to see if these responses can be even better with combination IO therapy.
Presented by: Dr. Rosenberg on behalf of Dr. Padmanee Sharma
Written by: Shreyas Joshi, MD, Fox Chase Cancer Center, Philadelphia, PA at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA