Variations and patterns in germline and somatic testing by age in ovarian, primary peritoneal, and fallopian tube cancer patients: a descriptive analysis in a large, real-world clinical and genetic data registry

Objective: To evaluate the relationship between genomic instability score and age distribution in ovarian, primary peritoneal, and fallopian tube cancers and to characterize age-related patterns in germline, homologous recombination deficiency (HRD), and somatic tumor testing using a large real-world clinical registry. Methods: Patients with ovarian, primary peritoneal, and fallopian tube cancers who underwent germline and/or somatic testing were identified from the Myriad Collaborative Research Registry (MCRR), version 4 (March 2025). Genomic instability scores (GIS) and tumor mutation profiles were analyzed across four age groups (<50, 50-59, 60-69, and ≥70 years). HRD positivity was defined as GIS ≥ 42. Testing patterns were evaluated by ordering specialty. Comparisons were performed using chi-square testing with significance defined as p < 0.05. Results: Among 110,119 patients with ovarian, peritoneal, or fallopian tube cancer, HRD positivity decreased with increasing age (36.2% in <50 years, 36.4% in 50-59 years, 30.9% in 60-69 years, and 24.2% in ≥70 years; p < 0.0001). Median GIS was similar across age groups but demonstrated narrower distribution ranges in older patients. Subgroup analysis of patients with intermediate GIS scores (35-41) showed increasing prevalence with advancing age. Gynecologic oncologists ordered significantly more HRD tests than medical oncologists; however, HRD positivity rates were similar between specialties. Peritoneal cancer diagnoses increased with age. Conclusion: Younger patients demonstrated higher rates of HRD positivity compared to older patients despite similar median GIS distributions. These findings may have implications for biomarker-driven therapeutic selection and clinical trial generalizability, particularly in older ovarian cancer populations. Further investigation is needed to understand age-related molecular differences and optimize testing and treatment strategies across age groups.