Up-front mutation detection in circulating tumor DNA by droplet digital PCR has added diagnostic value in lung cancer.

Identification of actionable mutations in advanced stage non-squamous non-small-cell lung cancer (NSCLC) patients is recommended by guidelines as it enables treatment with targeted therapies. In current practice, mutations are identified by next-generation sequencing of tumor DNA (tDNA-NGS), which requires tissue biopsies of sufficient quality. Alternatively, circulating tumor DNA (ctDNA) could be used for mutation analysis. This prospective, multicenter study establishes the diagnostic value of ctDNA analysis by droplet digital PCR (ctDNA-ddPCR) in patients with primary lung cancer. CtDNA from 458 primary lung cancer patients was analyzed using a panel of multiplex ddPCRs for EGFR (Ex19Del, G719S, L858R, L861Q and S768I), KRAS G12/G13 and BRAF V600 mutations. For 142 of 175 advanced stage non-squamous NSCLC patients tDNA-NGS results were available to compare to ctDNA-ddPCR. tDNA-NGS identified 98 mutations, of which ctDNA-ddPCR found 53 mutations (54%), including 32 of 45 (71%) targetable driver mutations. In 2 of these 142 patients, a mutation was found by ctDNA-ddPCR only. In 33 advanced stage patients lacking tDNA-NGS results, ctDNA-ddPCR detected 15 additional mutations, of which 7 targetable. Overall, ctDNA-ddPCR detected 70 mutations and tDNA-NGS 98 mutations in 175 advanced NSCLC patients. Using an up-front ctDNA-ddPCR strategy, followed by tDNA-NGS only if ctDNA-ddPCR analysis is negative, increases the number of mutations found from 98 to 115 (17%). At the same time, up-front ctDNA-ddPCR reduces tDNA-NGS analyses by 40%, decreasing the need to perform (additional) biopsies.

Sensitive cell-free tumor DNA analysis in supernatant pleural effusions supports therapy selection and disease monitoring of lung cancer patients.

Supernatant pleural effusions (PE) have shown to be a valuable source for the detection of driver mutations in circulating tumor DNA (ctDNA). In this prospective study, the clinical value of ctDNA analysis in supernatant PE to support therapy selection and disease monitoring in lung cancer patients is assessed. Paired PE and plasma samples were collected from lung cancer patients before initiation of therapy (N = 2) and from EGFR positive patients during therapy (N = 3). Supernatant PE and plasma were tested for mutations in EGFR, KRAS and BRAF by droplet digital PCR. In PE of two patients with suspected lung cancer, a KRAS mutation was detected with a 5- and 8-fold higher fractional abundance (FA) compared to plasma. For three patients with progressive disease during therapy, both the EGFR L858R and T790M mutations were detected in PE. However, in plasma only for two of these patients the L858R mutation was detected with a 46- and 14- fold lower FA, and only for one patient the T790M mutation was detected with a 8-fold lower FA. For one patient, longitudinal ctDNA analysis in PE revealed the T790M and L858R mutations already two months prior to detection of progressive disease by CT-scan. In this study, a higher ctDNA concentration and FA was obtained from PE compared to the corresponding blood samples, which enables more sensitive mutation analysis. Thus, PE is a valuable liquid biopsy, complementing plasma, for ctDNA analysis to support therapy selection and disease monitoring in lung cancer patients.

Circulating biomarkers for monitoring therapy response and detection of disease progression in lung cancer patients.

Liquid biopsies have become of interest as minimally invasive ways to monitor treatment response in lung cancer patients. Circulating tumor DNA (ctDNA) and protein biomarkers are evaluated for their added value in monitoring therapy response and early detection of disease progression. Plasma and serum samples of non-small cell or small cell lung cancer patients were analyzed for driver mutations in ctDNA (EGFR, KRAS or BRAF) using droplet digital PCR and protein biomarkers (CA125, CEA, CA15.3, Cyfra 21-1, HE4, NSE, proGRP and SCCA) using electrochemiluminescence immunoassays. Biomarker concentration changes were compared with the outcome of CT-scans during therapy. The median difference of the concentration of ctDNA, CA125 and Cyfra21-1 was significantly lower in patients with partial response (PR) compared to patients with progressive disease (PD) on the first evaluation CT-scan (P<0.001, P=0.042 and P=0.020, respectively). A substantial agreement between ctDNA or CA125 response and radiographic response was observed (k=0.692 and k=0.792, respectively). The median difference of the concentration of ctDNA and Cyfra21-1 was also significantly lower in PR patients compared to PD patients at the last CT-scan during therapy (P<0.001 and P=0.026, respectively). An almost perfect agreement between ctDNA and radiographic response (k=0.827) and a moderate agreement between Cyfra21-1 response and radiographic response was observed (k=0.553). Serial testing of the concentration of ctDNA, Cyfra21-1, and possibly CA125 could be a useful added tool for monitoring therapy response and early detection of disease progression in lung cancer patients.