Cancer patients could soon know within minutes whether their tumors will respond to chemotherapy, potentially eliminating weeks of ineffective treatment and accelerating personalized medicine. This breakthrough addresses a critical gap in oncology where determining drug sensitivity currently requires lengthy culture periods or waiting for clinical response indicators. The MetaRing biosensor employs surface-enhanced Raman spectroscopy to detect metabolic changes that occur when cancer cells encounter paclitaxel, a widely used chemotherapy drug. The device creates precisely engineered nanostructures through controlled evaporation, generating stable plasmonic hotspots that amplify molecular signals from minimal tissue samples. Testing across drug-resistant breast cancer cell lines, xenograft tumors, and patient biopsies revealed distinct metabolic fingerprints associated with treatment sensitivity, specifically involving arginine and methionine-cysteine pathway alterations. This metabolic reprogramming provides mechanistic insight into how cancer cells develop chemoresistance, moving beyond simple viability measurements to capture fundamental cellular responses. The technology achieved over 92% accuracy in classifying paclitaxel sensitivity across clinical cohorts using a lightweight neural network for pattern recognition. Unlike existing approaches that require cell culture expansion or complex sample preparation, MetaRing operates directly on fresh biopsy material in complex biological environments. This matrix robustness represents a significant technical advance, as most biosensors fail in protein-rich clinical samples. The 10-minute turnaround time could transform oncology workflows, enabling same-day treatment decisions rather than empirical drug selection. However, validation remains limited to paclitaxel and breast cancer, requiring broader studies across tumor types and chemotherapy classes before clinical implementation.