Introduction
Treating heavily pretreated metastatic breast cancer presents a profound clinical challenge. Clinicians frequently lack predictive biomarkers for cytotoxic drug responses. Consequently, they must select subsequent lines of therapy empirically, which often yields modest clinical benefits.
This issue becomes particularly acute in Triple Negative Breast Cancer (TNBC). Standard genomic-guided approaches regularly fail to identify actionable driver mutations in these patients. However, functional precision medicine platforms offer a novel alternative by assessing live tumor responses directly. This case study demonstrates how ex vivo drug sensitivity testing can successfully guide therapeutic selection for refractory disease.
Methodology: Ex Vivo Drug Testing via Optim.AI™
A patient initially received a stage III ER+/HER2- breast cancer diagnosis. Following surgery and multiple lines of metastatic therapy, the disease recurred and underwent a phenotypic transformation into TNBC. Next-generation sequencing revealed no targetable driver mutations.
To identify an effective regimen, clinicians performed a wedge resection of a left chest wall lesion. The laboratory isolated live tumor cells from this specimen and formed short term organoids.
Researchers co-cultured these organoids directly with a panel of oncology therapeutics. A proprietary small-data AI platform, Optim.AI™, then analyzed the resulting cell viability data. The platform ranks single agents and combinatorial regimens using a normalized cell viability score, where lower values indicate higher tumor sensitivity.
Case Report Results: Achieving a Complete Response
The functional precision medicine report revealed distinct tumor vulnerabilities. Standard therapies like abemaciclib and olaparib demonstrated resistance, showing elevated cell viability scores. In contrast, the patient’s tumor cells displayed ex vivo sensitivity to 5-fluorouracil (5-FU) based treatments.
Based on these predictive findings, clinicians initiated targeted treatment using Tegafur-Oteracil-Gimeracil (TS-1), an oral fluoropyrimidine formulation. The patient had previously experienced disease progression on multiple standard therapies, including advanced antibody-drug conjugates.
Following the initiation of the guided therapy, follow-up PET/CT imaging revealed a remarkable clinical outcome. The patient achieved a radiological Complete Response with the complete resolution of all previously active hypermetabolic lesions. Furthermore, the patient tolerated the regimen exceptionally well, reporting zero treatment-related adverse events.
Conclusion
Functional drug sensitivity testing could play a role in treatment prioritization for patients with multiple refractory cancers when the next line of treatment is uncertain.