CA125 test result, test-to-diagnosis interval and stage in ovarian cancer: a cohort study using electronic health records

Abstract

Background: Cancer-Antigen-125 (CA125) is recommended as a first-line investigation in women in UK General Practice with symptoms of possible ovarian cancer. Aim: To compare time between initial primary care CA125 test and diagnosis (test-to-diagnosis interval), tumour morphology and stage, in women with normal (<35U/ml) and abnormal (≥35U/ml) CA125 prior to ovarian cancer diagnosis. Design: Retrospective cohort study using routinely collected primary care and cancer registry data. Methods: Associations between CA125 result with test-to-diagnosis interval, stage and ovarian cancer morphology were examined. Results: 351 (77%) women had an abnormal and 105 (23%) a normal initial CA125 result prior to ovarian cancer diagnosis. Median test-to-diagnosis interval was 35 days (Interquartile range [IQR]:21-53) in those with abnormal, and 64 days (IQR:42-127) in those with normal CA125s. Tumour morphology differed by CA125 result, with indolent borderline tumours being less common in those with abnormal (n=47, 13%) than normal (n=51, 49%) CA125s (p<0.001). Staging data was available for 381 women. 106 of 304 (35%) women with abnormal CA125s and 66 of 77 (86%) women with normal CA125s were diagnosed at an early stage: normal CA125s were associated with early-stage diagnosis (Odds Ratio:12.1, 95% CI:5.8-25.1, p<0.001). Conclusion: Despite experiencing longer intervals between testing and diagnosis, women with normal CA125s more frequently had indolent tumours and were more commonly diagnosed at an early stage, compared to those with abnormal CA125s. Whilst more sensitive testing approaches might expedite diagnosis for some women, it is not known whether this would translate to earlier stage diagnosis and improved survival.