The agreement provides reimbursement for the CNSide cerebrospinal fluid assay, increasing total covered lives to 81 million.
Plus Therapeutics announced a new payer coverage agreement with Blue Shield of California for its CNSide cerebrospinal fluid (CSF) tumor cell enumeration assay. Effective April 2026, the agreement provides reimbursement for patients with metastatic central nervous system (CNS) cancers.
Blue Shield of California joins a list of national and regional payers, including United Healthcare, Humana, and Highmark, that provide coverage for the assay. The addition of Blue Shield of California expands total covered lives for the test from approximately 75 million to 81 million. This move represents progress toward the company’s 2026 objective of 150 million covered lives while expanding patient access across the US.
“This agreement with Blue Shield of California represents another important step in expanding payer coverage and access to CNSide for patients with leptomeningeal metastases,” says Russ Havranek, executive vice president of corporate and commercial strategy at Plus Therapeutics, in a release. “We continue to execute on our strategy to broaden reimbursement, support physician adoption, and improve outcomes for patients with difficult-to-diagnose CNS cancers.”
The assay platform enables earlier and more accurate detection and monitoring of leptomeningeal metastases compared to conventional CSF cytology. According to the company, the platform supports rapid diagnosis, treatment monitoring, and treatment guidance. The clinical utility of the assay over standard of care has been documented in nine peer-reviewed publications and the FORESEE clinical trial.
Health economic analyses have shown that earlier detection enabled by the test reduces overall leptomeningeal metastases-related healthcare costs by approximately 40%, driven by earlier detection and treatment optimization.
Since its commercial launch in 2020, more than 11,000 tests have been performed at over 120 US cancer institutions. The assay delivers 92% sensitivity and 95% specificity, while influencing treatment decisions in 90% of cases.
The test is available exclusively through CNSide Diagnostics, a wholly owned subsidiary of Plus Therapeutics, as a laboratory-developed test provided to health care professionals in the US. The assay is designed to identify tumor cells that have metastasized to the CNS in patients with carcinomas and melanomas, providing quantitative analysis of the CSF to inform patient management.
