Biopsy Expansion Data Supports Use of Archival Tumor Tissue for Ovarian Cancer Diagnosis

Data from a phase 1 biopsy expansion demonstrated that archival tumor tissue can reliably identify patients with folate receptor alpha (FRα)-positive platinum-resistant ovarian cancer.

For the biopsy expansion cohort, investigators sought to characterize FRα expression in archival tumor tissue and in pre- and post-treatment biopsy samples obtained from a heterogeneous population of patients with relapsed epithelial ovarian cancer (EOC), according to a press release.

The investigators sought to determine the concordance rate between archival tissue and pre-treatment biopsy FRα expression levels. They also compared changes in FRα expression levels before and after treatment with mirvetuximab soravtansine in biopsy samples.

A total of 27 heavily pretreated patients were enrolled in the cohort based on FRα expression levels in archival tumor tissue. Prior to receiving mirvetuximab soravtansine, participants underwent a pre-treatment biopsy and a post-treatment biopsy after 2 doses of mirvetuximab soravtansine.

Of the 21 evaluable pre-treatment samples, 15 met the eligibility criterion for the biopsy expansion cohort, which resulted in 71% concordance with archival tumor tissue.

Due to insufficient tumor cells present in the specimens, 22% of patients did not have pre-treatment biopsies that were evaluable for FRα immunohistochemistry. Furthermore, biopsies taken before and following 2 doses of mirvetuximab soravtansine showed similar FRα expression levels.

The findings indicated that a comparison of FRα expression levels in pre-treatment biopsies versus archival samples supports the use of archival tumor tissue for patient selection, according to the release. Furthermore, it supports the use of pre-treatment biopsy for patient selection if archival tumor tissue is not available for evaluation.

The safety profile of the cohort was consistent with previously reported data for mirvetuximab soravtansine-treated EOC patients across the phase 1 study, with predominately grade 1 and 2 adverse events.

The data were presented at the Society of Gynecologic Oncology annual meeting in National Harbor, Maryland.

“In the Phase 3 FORWARD I registration trial for mirvetuximab soravtansine, FRα expression for patient selection is being assessed based on archival tumor tissue samples,” said Anna Berkenblit, MD, vice president and chief medical officer of ImmunoGen. “The results being presented at SGO support this strategy to select patients for our Phase 3 FORWARD I trial. More broadly, the data being presented confirm that in this heavily pretreated cohort, mirvetuximab soravtansine is well tolerated and that the higher the FRα expression, the greater the anti-tumor activity.”