• SPR‑POF biosensor detects serum MAVS in SCLC chemo-immunotherapy patients. • MAVS levels 10 × higher in best responders vs non-responders SCLC patients. • Biosensor LOD 0.13 nM with high selectivity. • Portable, low-cost platform suitable for POCT. • First clinical application of MAVS biosensing in oncology. Small cell lung cancer (SCLC) is an aggressive neuroendocrine tumor with poor prognosis and limited benefit from immune checkpoint inhibitors (ICIs). Biomarker-driven patient stratification has been hindered by small biopsy samples, high tumor heterogeneity, and the limited predictive value of PD-L1 and tumor mutation burden. Mitochondrial antiviral-signaling protein (MAVS) has emerged as a potential immune activation marker, particularly in patients receiving DNA-damaging therapies. We report a proof-of-concept clinical study evaluating a surface plasmon resonance–plastic optical fiber (SPR‑POF) biosensor functionalized with anti-MAVS antibodies to detect the protein in serum from SCLC patients undergoing chemo-immunotherapy, with or without radiotherapy. The biosensor achieved a limit of detection of 0.13 nM in human diluted serum and demonstrated high selectivity against common serum proteins. In a cohort stratified as best responders (disease control >6 months) and non-responders (progressive disease as best response), MAVS levels measured in responders were on average tenfold higher than in non-responders, consistent with previous preclinical PBMC and western blot data. The SPR‑POF platform demonstrated portability, cost-effectiveness (estimated 5 USD/unit), and operational simplicity, highlighting its potential for point-of-care testing (POCT) applications. Although limited by small patient numbers, these findings support MAVS as a promising predictive biomarker in SCLC, warranting validation in larger prospective studies.
Amato et al. (Sun,) studied this question.