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Palmetto Draft LCD Proposes Limited Coverage for Guardant360

NEW YORK (GenomeWeb) – Medicare contractor Palmetto GBA has released a draft local coverage determination for Guardant Health's comprehensive liquid biopsy test Guardant360, proposing limited coverage for the test in patients with advanced non-small cell lung cancer.

According to the LCD, released under Palmetto's MolDx program, coverage for the test would be restricted to patients with cancers at stage IIIB or higher, and performed either at diagnosis or at progression.

For Guardant360 to be covered at diagnosis, patients must not have been genomically tested for EGFR alterations, ALK and ROS1 rearrangements, or PD-L1 expression, and they must not be eligible for tissue-based testing — either because their biopsy tissue is insufficient, or because a biopsy is not possible for medical reasons.

At progression, the LCD proposes coverage for patients who, again, have never been tested for the targets in question and for whom tissue-based testing is infeasible. It also provides coverage for patients who are progressing on an EGFR tyrosine kinase inhibitor regardless of their history of genetic testing.

Repeat testing in the context of therapeutic monitoring is not a Medicare benefit, according to the draft. Neither is use of Guardant360 for assessing germline variants.

Supporting the draft, Palmetto cited clinical practice guidelines from the National Comprehensive Cancer Network, which recommend "broader molecular profiling" and state that plasma biopsy should be considered if tissue biopsy is not feasible. The draft also mandates that physicians should consider seeking tissue-based testing if Guardant360 fails to detect a genetic alteration in patients circulating cell-free DNA, or if the test fails due to insufficient or undetectable tumor DNA.

The LCD specifically cites the indications for use of Roche's plasma-based Cobas EGFR mutation test, which was approved by the US Food and Drug Administration last year, saying that considerations for follow-up tissue testing in the context of Guardant360 should follow those outlined for the Roche assay.

The draft does recognize that plasma-based genomic testing presents analytical challenges that tissue testing does not, primarily due to the dilution of circulating tumor DNA by normal cell-free DNA, resulting in low variant allele fractions. However, Palmetto wrote that the analytical performance characteristics of Guardant360 are consistent with MolDx's "Analytical Performance Specifications for Qualitative Tumor-only Somatic Variant Detection using Circulating Tumor DNA."

The LCD also calls the clinical utility of Guardant360 testing for patients with advanced NSCLC at diagnosis or at progression "quite promising," at least as defined in the intended use specified by the draft. Guardant360 has also demonstrated targeted therapy response rates similar to tissue-detected genomic targets in seven different published NSCLC studies, Palmetto wrote, with the expectation that forthcoming prospective clinical studies will demonstrate improved patient clinical outcomes.

Continued coverage for Guardant360 testing is dependent on annual review by this contractor of these expected data and publications, Palmetto concluded.