P3.04-02 Early Plasma ctDNA Response Anticipates Clinical Response to First-Line Immunotherapy in Advanced NSCLC

P3.04-02 Early Plasma ctDNA Response Anticipates Clinical Response to First-Line Immunotherapy in Advanced NSCLC

Background: Shedding of circulating tumor DNA (ctDNA) into plasma can be an independent prognostic indicator in lung cancer, and changes in plasma ctDNA levels correlate with response to targeted therapy. We hypothesized that serial assessment of plasma ctDNA by next generation sequencing (NGS) would enable early detection of response to immunotherapy in NSCLC.

Method: Patients with advanced NSCLC who received first-line treatment with pembrolizumab alone or in combination with platinum doublet chemotherapy at the Dana-Farber Cancer Institute were enrolled in this study. Plasma collected from patients prior to starting therapy and again at 3 and 3 weeks after starting therapy was analyzed by NGS using enhanced tagged-amplicon sequencing of hotspots and coding regions from 36 genes (InVisionSeq). The trends of the ctDNA allele frequency were correlated with radiographic responses to therapy.

Result: Serial plasma samples were collected on 21 patients with the following characteristics: 67% female, median age 62, 90% adenocarcinoma, 10% squamous cell carcinoma. Pembrolizumab was administered as monotherapy to 18 (86%) patients and in combination with platinum/pemetrexed in 3 (14%) patients for a median of 6 cycles. Among the 8 (38%) patients with no detectable ctDNA at baseline, 5 patients who maintained no detectable ctDNA during serial analyses responded to treatment, and 3 patients with emergence of ctDNA within the first 6 weeks of treatment initiation experienced progressive disease. In the 13 (62%) patients with detectable ctDNA at baseline, radiographic responses were preceded by earlier changes in ctDNA allele frequency. Six of 7 patients with >50% decreases in ctDNA allele fraction responded to treatment while 4 of 6 patients with progressive disease had increases in ctDNA within 6 weeks.

Conclusion: In advanced NSCLC treated with first-line immunotherapy, rapid decreases and clearance of ctDNA correlated with clinical benefit, while increasing or newly detectable ctDNA was a harbinger of progressive disease. These results suggest a potential role for ctDNA as an early pharmacodynamic biomarker of response or resistance to immunotherapies.


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