Correlation of cell-free circulating DNA, RNA, and PD-L1 from plasma with clinical response in patients with metastatic lung and breast cancers.

Abstract

11550 Background: There is an unmet need to evaluate tumor response by other means than radiology tests. Changes in gene expression, allele-fractions of mutations, PDL-1 expression and levels of cell free DNA [DNA] or RNA [RNA] in plasma might be useful for monitoring disease state and predicting outcome to anti-tumoral therapy. Methods: We measured serial levels of plasma DNA/RNA in metastatic patients (pts) with NSCLC and breast cancers undergoing treatment and correlated them with response (CR/PR/SD/PD) seen by CT scans. We also monitored PD-L1 expression in NSCLC pts treated with immunotherapy. DNA/RNA were extracted from plasma. RNA was reverse transcribed with random primers to cDNA. Levels of DNA/RNA were determined by RT-qPCR. Results: 52 pts were enrolled (28 breast/24 NSCLC). Breast group: 39% (11/28) were Caucasian (NHW) and 36% (10/28) Hispanic (H). 20 pts completed first two cycles of therapy: 2 pts had PR and showed no change (NC) or decrease (DEC) in levels of DNA/RNA. 11pts achieved SD, 9 had NC levels of DNA/RNA. Pts with PD: 5/6 underwent significant increase (INC) in DNA/RNA levels. Overall, among breast pts, there was an 84% (16/19) agreement between response and levels of DNA/RNA. These were correlated with one another ( r = 0.7002, p< 0.0001). NSCLC group: 71% (16/24) were NHW and 25% (6/24) H. Non-SQCC were 87% (21/24). 20 pts had CT scans. One pt had PR with DEC levels of DNA/RNA. 10 pts achieved SD, all showed DEC or NC levels of DNA/RNA. 8 pts had PD, 6 of them had INC in DNA/RNA levels even 7 weeks prior to PD. Among NSCLC pts, there was a 90% (17/19) agreement in response and levels of DNA/RNA. These were correlated with one another ( r= 0.6231, p< 0.0001). In 5 pts PD-L1 expression remained stable when CT scans showed SD or PR. Conclusions: There is a strong correlation between clinical responses with changes in plasma levels of DNA/RNA in pts with NSCLC (90%) and breast cancer (84%). Some of these were documented weeks before imaging was done. cfRNA is as effective as cfDNA as predictive tool for response. Plasma PDL-1 expression is a new tool to monitor immunotherapy response.