Immunotherapy Treatments After Progression With Cisplatin
Cytotoxic chemotherapy in the second-line setting with disease progression following platinum-based treatment has shown dismal responses, with a median OS of about 6 to 7 months.7 Immunotherapy provides an effective and a much-needed option in this scenario.
Five antibodies targeting the PD-1/PD-L1 pathway, pembrolizumab, nivolumab, atezolizumab, avelumab and durvalumab, have been granted FDA approval for patients who have progressed during or after platinum-based therapy (Table).3 In the phase 3 Keynote-045 trial, 542 patients were randomly assigned to receive either pembrolizumab 200 mg administered every 3 weeks or investigator’s choice chemotherapy (paclitaxel, docetaxel, or vinflunine).7 Median OS was 10.3 months in the pembrolizumab group and 7.4 months in the chemotherapy group (hazard ratio for death, 0.73; P = .002). Serious (grade 3 or above) treatment-related AEs were significantly less frequent with pembrolizumab (15% vs 49.4%).7 In a phase 2 trial, 270 patients were treated with nivolumab, a PD-1 inhibitor, at a dose of 3 mg/kg given every 2 weeks.8 The ORR was 19.6%, while the median OS for the entire cohort was 7 months. Responses were seen at all levels of PD-L1 expression, although in patients whose tumor expressed PD-L1 ≥1%, median OS was 11.3 months.8
It should be noted that in a large phase 3 trial comparing atezolizumab with chemotherapy in the second-line setting, ORR and OS were not statistically different between the 2 groups, although the duration of response was longer with atezolizumab.9 In early phase trials, avelumab and durvalumab, both PD-L1 inhibitors showed an ORR of about 17%, with higher ORR seen in patients with tumors positive for PD-L1 expression.10,11 The AE profile of immune checkpoint inhibitors is relatively favorable in clinical trials. The American Society of Clinical Oncology and National Comprehensive Cancer Network have jointly published evidence-based guidelines for the management of their immune related AEs.12
Future Directions
Several challenges have emerged with immunotherapy treatments. One issue is the relatively low ORRs for immune checkpoint inhibitors, ranging from 13.4% to 24% depending on the trial. Therefore, there is a need to identify reliable biomarkers and selection criteria to predict their efficacy and improve patient selection. Although tumor PD-L1 expression has shown some usefulness in this setting, responses have been noted in patients whose tumors have low or no expression of PD-L1. This low predictive accuracy is caused by several factors, including PD-L1 intratumor expression heterogeneity, primary vs metastatic site PD-L1 expression heterogeneity, lack of consensus on which PD-L1 assays and which value cutoffs to use, and the differences seen in marker expression depending on the freshness of the tissue specimen.
Other predictive biomarkers with potential include tumor gene expression profiles/tumor mutational load, T-cell and B-cell signatures. The optimal imaging modality and timing of this imaging for response assessment also is uncertain. So-called tumor pseudo-progression seen on imaging after treatment with these agents as a result of the immune/inflammatory response to the tumor is now a well-recognized phenomenon, but it can be challenging to differentiate from true disease progression. Other challenges include deciding on which immune checkpoint inhibitor to use given a lack of head-to-head comparisons of these immunotherapeutic agents, finding the proper drug doses to maximize efficacy, as well as determining the optimal duration of treatment in patients with continued response to immunotherapy. Many oncologists continue these treatments for up to 2 years in the setting of a significant or complete response.