Application of precision medicine based on next-generation sequencing and immunohistochemistry in ovarian cancer: a real-world experience

Objective: To evaluate the landscape of gene alterations and immunohistochemistry (IHC) profiles of patients with ovarian cancer for targeted therapy and investigate the real-world experience of applying precision medicine. Methods: Patients diagnosed with ovarian cancer between January 2015 and May 2021 at Severance Hospital and who underwent tumor next-generation sequencing (NGS) were reviewed. Data on germline mutation, IHC markers for mismatch repair deficiency (MMRd), programmed death ligand 1 (PD-L1) expression, and human epidermal growth factor receptor 2 (HER2) expression were acquired. The use of matched therapy and its clinical outcomes were evaluated. Results: Of the 512 patients who underwent tumor NGS, 403 underwent panel-based germline testing. In patients who underwent both tests, tumor NGS identified 39 patients (9.7%) with BRCA mutations and 16 patients (4.0%) with other homologous recombination repair (HRR)-associated gene mutations, which were not found in germline testing. The most common single nucleotide variants were TP53 (82.2%), ARID1A (10.4%), PIK3CA (9.7%), and KRAS (8.4%). Copy number aberrations were found in 122 patients. MMRd was found in 3.2% of patients, high PD-L1 expression in 10.1%, and HER2 overexpression in 6.5%. Subsequently, 75 patients (14.6%) received a poly (ADP-ribose) polymerase inhibitor based on BRCA mutation and 11 patients (2.1%) based on other HRR-associated gene mutations. Six patients (1.2%) with MMRd underwent immunotherapy. Twenty-eight patients (5.5%) received other matched therapies targeting HER2, fibroblast growth factor receptor, folate receptor alpha, RAS, and PIK3CA. Conclusion: A comprehensive review of germline mutation, IHC, and tumor NGS helped identify candidates for precision therapy in patients with ovarian cancer, a proportion of whom received matched therapy.