Mesothelin and HE4 are novel ovarian cancer biomarkers that may have utility for early detection. When tested as diagnostic markers using samples collected at clinical diagnosis from patients unselected for ovarian cancer risk both markers discriminate ovarian cases from healthy and benign controls at high levels of specificity. We undertook this study to evaluate if the diagnostic performance of CA125, mesothelin and HE4 was affected by the ovarian cancer risk status as high risk women are ideal candidates for early evaluation of new ovarian cancer screening tests. We recognize that although high performance in diagnostic samples is a necessary characteristic, the true utility of an early detection marker depends on its behavior prior to clinical diagnosis. We sought to determine if the markers were suitable for further testing in women at high risk since women who are at high risk for ovarian cancer are most likely to participate in a screening program for ovarian cancer. Our findings suggest that further studies evaluating early detection potential of the markers we tested in high risk women are warranted and that the findings from these studies may be generalizable to women in the general population.
We used self-report of personal and family cancer history to a standardized questionnaire to obtain information for risk classification. Women were asked an extensive series of questions about diagnosis and age at diagnosis of ovarian, breast, colon and other cancers in first and second degree family members. We also asked women if they had been tested for BRCA 1 and 2 mutations and if a deleterious mutation or variant of uncertain significance was identified. However, only 48 (7%) of the women included herein reported they had been tested for the mutations and 28 of these women (58%) reported having a positive test.
A limitation of our study is that we were not able to validate self-report of information used to characterize risk status. It is possible that either direct interview or review of personal and family medical records might have provided more complete or accurate information and better risk classification. Misclassification could have occurred if a participant believed a relative’s cancer was ovarian when in fact it arose in another site. It is also possible women may have been inappropriately classified as being average risk if they chose to withhold information about genetic testing because of concerns about confidentiality.
The classification system we used to characterize women at high risk identifies a heterogeneous group with respect to their true risk of ovarian cancer. Ovarian cancer risk in this group spans from roughly a 10% lifetime risk for developing ovarian cancer for women meeting minimal criteria to perhaps as high as 60% lifetime risk for BRCA1 mutation carriers. A more homogeneous population, particularly one limited to mutation carriers, might be more informative. However our criteria for identifying women as high risk are generally accepted clinically and consistent with eligibility criteria used to select women for enrollment into large multi-center, prospective ovarian cancer screening studies targeting women at high risk (28
The average and high risk groups in this study are well balanced for most of the baseline demographic information that was collected. Self-report of use of hormone replacement therapy (HRT) among healthy control women did vary by risk status (p <0.01). The difference remained significant even after women responding “unknown” to having ever used HRT were removed from the analysis, suggesting most of the difference is related to a higher proportion of high risk women reporting having ever used HRT. More frequent reported use of HRT among the high risk women is probably explained by the fact that a greater proportion of these women were post-menopausal (67% vs. 35%; p=.53). We also identified differences in ethnicity between high and average risk healthy controls however these differences were not significant when women who reported their race as unknown were removed from the analysis.
Interestingly, mean levels of CA125 were lower in high risk as compared to average risk healthy controls. Mean CA125 levels fall substantially after menopause (30
), and the lower CA levels in high risk controls may be explained by the high proportion of post-menopausal women in the high- risk group. In a prior report we noted that CA125 levels in healthy post-menopausal high risk women were affected by ovarian cancer risk factors including talc use and parity although the effects were minor; these parameters were not evaluated in the current report (31
). Pauler reported that CA125 levels in healthy women vary based on personal characteristics including age, race, smoking, caffeine intake, age at menarche and menopause status (30
). Factors evaluated in this report including age and race did not vary by risk group.
We found that for mucinous ovarian cancer cases mesothelin and HE4 levels were higher in high risk as compared to average risk women. This result could be spurious as the total number of mucinous cancers in the cohort was small (n=6); and there were only 2 mucinous cancers in the high risk group. Differences in marker levels could not be explained by either tumor volume or stage as these factors vary between the two groups (data not shown).
The overall diagnostic performance of the markers estimated using the area under the ROC curve did not vary by risk status. When ovarian cancer cases were compared to healthy controls the AUC values for average and high risk women were nearly identical (.939 vs. .939 for CA 125; .793 vs. .734 for mesothelin; and .928 and .931 for HE4). The findings were similar although the AUC values were lower when cases were compared to benign controls. The reduction in AUC is not surprising as some benign tumors are known to emit low levels of the markers. At high levels of specificity mesothelin appeared to perform better in average risk women and HE4 performed better in high risk women although the differences were relatively minor, not statistically significant, and may be influenced by the sparseness of the data in this portion of the curve. For mesothelin the sensitivity at 98% specificity for ovarian cases vs. healthy controls was 44.1 % and 31.71% for average and risk women respectively. For HE4 the values were 68.3% for average and 82.9% for high risk women. The direction and magnitude of the differences did not change when the analysis was limited to serous cancers (data not shown). We chose not to evaluate marker combinations because we believe that optimizing marker panels using diagnostic samples collected from symptomatic patients is not likely to be relevant for early detection. However based on our data it is unlikely that the diagnostic performance of a combination marker that includes CA125, mesothelin and/or HE4 will vary by patient risk status.