Conclusion. The addition of consolidative durvalumab following completion of concurrent chemoradiotherapy in patients with stage III, locally advanced NSCLC significantly improved PFS without a significant increase in treatment-related adverse events.
Commentary
Pre-clinical evidence has suggested that chemotherapy and radiation therapy may lead to upregulation of PD-L1 expression by tumor cells leading to increased PD-L1 mediated T cell apoptosis [1,2]. Given prior studies documenting PD-L1 expression as a predictive biomarker for response to durvalumab, the authors of the current trial hypothesized that the addition of durvalumab after chemoradiotherapy would provide clinical benefit likely mediated by upregulation of PD-L1. The results from this pre-planned interim analysis show a significant improvement in progression-free survival with the addition of durvalumab with a 48% decrease in the risk of progression. This benefit was noted across all patient subgroups. In addition, responses to durvalumab were durable, with 72% of the patients who responded having an ongoing response at 18 months. Interestingly, the response to durvalumab was independent of PD-L1 expression, which is in contrast to previous studies showing PD-L1 expression to be a good biomarker for durvalumab response [3].
The results of the PACIFIC trial represent a clinically meaningful benefit and suggests an excellent option for patients with unresectable stage III NSCLC. One important point to highlight is that the addition of durvalumab was well tolerated and did not appear to significantly increase the rate of severe adverse events. Of particular interest is the similar rates of grade 3 or 4 pneumonitis, which appeared to be around 3% for each group. Overall survival data remain immature at the time of this analysis; however, given the acceptable toxicity profile and improved PFS this combination should be considered for these patients in clinical practice. Ongoing trials are underway to evaluate the role of single-agent durvalumab in the front-line setting for NSCLC.
Applications for Clinical Practice
In patients with unresectable stage III NSCLC who have no evidence of disease progression following completion of chemoradiotherapy, the addition of durvalumab provided a significant and clinically meaningful improvement in progression-free survival without an increase in serious adverse events. While the overall survival data is immature, the 48% improvement in progression-free survival supports the incorporation of durvalumab into standard practice in this patient population.
—Daniel Isaac, DO, MS