CCNE1 amplification among metastatic sites in patients with gynecologic high-grade serous carcinoma

•CCNE1 amplification is conserved among metastatic sites in CCNE1-amplified high-grade serous carcinomas.•Limited CCNE1 copy number heterogeneity among CCNE1-amplified cases suggests some genomic change during metastasis.•Digital droplet PCR can be used to quantify CCNE1 copy number from archival specimens of high-grade serous carcinomas. We sought to characterize the variability of CCNE1 amplification among metastatic sites of CCNE1 amplified high grade serous carcinoma (HGSC) cases to investigate the feasibility of targeting this alteration for therapeutic purposes. Patients with CCNE1 amplified HGSC who underwent surgical cytoreduction with metastatic sites were identified from institutional molecular profiling reports and a population of HGSC cases screened using digital droplet PCR (ddPCR). Cases with normal CCNE1 copy number were included as controls. Slides from metastatic sites were cut from formalin-fixed paraffin-embedded tissue blocks, dissected for tumor of > 50% purity, and underwent DNA extraction. CCNE1 copy number was determined by ddPCR. Tumor purity was confirmed with mutant TP53 allele fraction from targeted massively parallel sequencing. Four of 15 patients from an institutional database screened by ddPCR were found to have CCNE1 amplification. Three additional patients were identified from a query of institutional commercial clinical reports. Among these 7 CCNE1 amplified cases (2 uterine, 5 ovarian), 5 showed preservation of CCNE1 amplification (copy number > 5) among all metastatic sites. The remaining 2 cases had multiple metastatic sites without preserved CCNE1 amplification. Non-amplified cases had predominantly normal CCNE1 copy number across metastatic sites. CCNE1 amplification is an early genomic event in HGSC and is preserved in most metastatic sites suggesting a uniform response to pathway targeting therapies.