ABSTRACT
BACKGROUND: Transcriptomic subtyping holds promise for personalized therapy in extensive-stage small-cell lung cancer (ES-SCLC). In this study, we aimed to assess intratumoral transcriptomic subtype diversity and to identify biomarkers of long-term chemoimmunotherapy benefit in human ES-SCLC. PATIENTS AND METHODS: We analyzed tumor samples from 58 ES-SCLC patients enrolled in two multicenter single-arm phase IIIb studies evaluating front-line chemoimmunotherapy in Spain: n=32 from the IMfirst trial, and n=26 from the CANTABRICO trial. We utilized the GeoMxTM DSP system to perform multi-region transcriptomic analysis. For subtype classification, we performed hierarchical clustering using the relative expression of ASCL1 (SCLC-A), NEUROD1 (SCLC-N), POU2F3 (SCLC-P), and YAP1 (SCLC-Y). RESULTS: Subtype distribution was similar between both cohorts, except for SCLC-P, not identified in the CANTABRICO_DSP cohort. A total of 44% of the patients in both cohorts had tumors with multiple co-existing transcriptional subtypes. Transcriptional subtypes or subtype heterogeneity were not associated with outcomes. Most potential targets did not show subtype-specific expression. Consistently in both cohorts, tumors from patients with long-term benefit (time to progression ³12 months) contained an IFNg-dominated mRNA profile, including enhanced capacity for antigen presentation. Hypoxia and glycolytic pathways were associated with resistance to chemoimmunotherapy. CONCLUSIONS: This work suggests that intratumoral heterogeneity, inconsistent association with outcome, and unclear subtype-specific target expression might be significant challenges for subtype-based precision oncology in SCLC. Pre-existing IFNg-driven immunity and mitochondrial metabolism seem correlates of long-term efficacy in this study, although the absence of a chemotherapy control arm precludes concluding that these are predictive features specific for immunotherapy.
ABSTRACT
INTRODUCTION: Precision medicine has revolutionized the understanding and treatment of cancer by identifying subsets of patients who are amenable to specific treatments according to their molecular characteristics, as exemplified by epidermal growth factor receptor (EGFR) mutations in non-small cell lung cancer (NSCLC). Although tissue biopsy is the gold standard for determining molecular alterations in tumors, its limitations have prompted the development of new techniques for studying tumor biomarkers in liquid biopsies, such as mutation analysis in cell-free DNA (cfDNA). cfDNA analysis can accurately determine tumor progression and prognosis and more effectively identify appropriate targeted therapies. However, cfDNA is vulnerable, particularly during plasma sample shipping. OBJECTIVE: We compared the cell- and DNA-stabilizing properties of cell-free DNA blood collection tubes (BCTs) with those of the traditional shipping method (frozen plasma) for EGFR mutation testing using the cobas® EGFR Mutation Test v2 in a prospective cohort of 49 patients from three different Spanish hospitals. METHODS: In total, 98 NSCLC samples, two from each patient, were studied; five of the 49 cases were considered invalid by cobas® with one of the two shipping methods analyzed. After excluding these samples, we analyzed 88 samples from 44 patients. Considering the current methodology (frozen plasma) for sending samples as the gold standard, we evaluated the sensitivity and specificity of cfDNA BCT shipment. RESULTS: The global agreement between the two methods was 95.4%, with 100% sensitivity and 94.6% specificity for the cfDNA BCTs. cfDNA BCTs had a positive predictive value of 81.8% and negative predictive value of 100%. CONCLUSION: cfDNA BCTs have the same sensitivity for EGFR mutation analysis in liquid biopsy as the current methodology and very high specificity. They also have some additional advantages in terms of collection and further shipment. Therefore, cfDNA BCTs can be perfectly incorporated into the routine practice for EGFR mutation determination. FUNDING: Roche Farma S.A., Spain.
