Arjun Vasant Balar, MD
Patients with metastatic urothelial carcinoma (mUC) who were ineligible for standard cisplatin-based chemotherapy achieved a 24% reduction in tumor size and had a median survival of 14.8 months after taking the immunotherapy agent atezolizumab (Tecentriq), according to phase II clinical trial results presented at the 2016 ASCO Annual Meeting.1
Atezolizumab became the first and thus far only PD-L1 inhibitor to gain approval in mid-May when the FDA authorized its use for patients with locally advanced or mUC whose disease progressed during or after platinum-based chemotherapy, or within 12 months of receiving platinum-containing chemotherapy, either before or after surgery.
At ASCO, lead study author Arjun Vasant Balar, MD, presented data from cohort 1 of the single-arm IMVigor 210 study, which included 119 patients in the first-line setting who were not candidates for cisplatin therapy (NCT02108652).
Cisplatin is the only treatment in mUC that has demonstrated a survival benefit, Balar, who is assistant professor of Medicine at the New York University Langone Medical Center and director of Genitourinary Medical Oncology at the NYU Perlmutter Cancer Center, said during an ASCO presscast.
During the trial, atezolizumab was administered at 1200 mg every 3 weeks until progression. Balar reported that the objective response rate (ORR) was 24%, with 75% of these responses (21 of 28 patients) still ongoing. The complete response rate was 7%, with the partial response rate reported at 17%.
Cisplatin ineligibilty was defined as 1 or more of the following factors: impaired kidney function (GFR <60 mL/min but >30): peripheral neuropathy, or hearing loss grade ≥2; or ECOG PS2 performance status.
Currently, treatment regimens in this setting are heterogeneous and are characterized by short response durations, with many patients managed with best supportive care only.
“I would underscore the importance of this study because it is looking at cisplatin-ineligible patients as opposed to carboplatin-treated patients,” said Charles Ryan, MD, professor of Clinical Medicine and Urology and Program Leader, Genitourinary Medical Oncology, at the UCSF Helen Diller Family Comprehensive Cancer Center.
“It is a substantial patient population in bladder cancer. There are many patients who are cisplatin-ineligible,” continued Ryan, who served as an ASCO expert during the presscast.
Patients in cohort 1 had a median age of 73 years, and 21% were 80 years and older. Eighteen percent reported prior systemic therapy (21% of whom reported receiving neoadjuvant treatment), 10% had received radiotherapy, and 66% reported visceral metastases.
Centrally assessed PD-L1 on tumor infiltrating immune cells (IC; SP142 IHC assay) was scored IC2/3, 1, or 0. “We observed that response was seen in all subgroups including complete response [CR] in all subgroups, and this was at a median follow up of 14.4 months,” said Balar. The primary efficacy endpoint was confirmed ORR assessed per RECIST v1.1 by central independent.
Atezolizumab was generally well tolerated. The investigators reported 6% of patients withdrawing from study because of adverse effects (AEs). Most AEs were grade 1 or 2; there was 1 case of a grade 5 AE (sepsis). Thirty-five percent of patients experienced an AE that led to dose interruption. In comparison to real world studies and clinical trials, atezolizumab compared favorably with historic data involving cisplatin-ineligible patients, reported the researchers.3
IMVigor 210 included 2 groups of patients: those receiving atezolizumab as a second-line therapy and those receiving atezolizumab as an upfront treatment. The researchers have previously reported results from the second-line therapy group. Based on those results, the FDA granted atezolizumab an accelerated approval in second-line and later settings. The approval was based on data in which atezolizumab had an ORR of 14.8% in patients with locally advanced or mUC, regardless of PD-L1 expression.2
“Currently, the FDA label indicates that Tecentriq should be used in patients who have progressed on prior platinum-based chemotherapy, which includes carboplatin- and cisplatin-based treatment. The indication is agnostic to the type of platinum,” said Balar.
The findings presented at ASCO would suggest a first-line setting for the agent in the future. “My study, which looked at cohort 1, is really an exploratory cohort. The survival data are very provocative, but the data are still immature. I do think there is a benefit there, but until we have comparative data, it is going to be difficult to compare with chemotherapy,” said Balar.
Balar was cautiously optimistic, however. “Do I envision a time when PD-1 or PD-L1 targeted therapy in the frontline setting is possible? Yes, absolutely. I think that is where the field is going. We just need the trials to show it.”