Defining Women at High Risk of Ovarian Cancer Free

In Response:

Drs. Swisher and King comment on strategies we applied to define risk, culture epithelial cells, and interpret the literature dealing with women at risk of ovarian cancer. We agree that we should have better stated what we meant: that the current genetic screening methods “cannot accurately identify all at risk patients…” We also accept that, theoretically, all of the subjects in our study could have carried cryptic BRCA1 mutations. In practice, women with strong family histories of ovarian cancer whose BRCA1/BRCA2 results are uninformative have little opportunity to gauge their risk. Our study provides a foundation for considering a new approach to this circumstance.

Indeed, we are testing these methods in women known to carry BRCA1 mutations, but not to “validate” our findings. Any result will be informative. We may learn that certain BRCA1 and BRCA2 mutations can influence FANCD2 gene expression or that only specific BRCA1 mutations influence FANCD2 gene expression. Remember that we have reported tissue-specific genetic instability (1); thus, if BRCA1 and/or BRCA2 control FANCD2 expression in a tissue-specific way, we will better understand tissue-specific ovarian and breast carcinogenesis, a problem that the BRCA field has not yet solved. If BRCA gene dysfunction has no effect on FANCD2 expression, we would conclude that genes other than BRCA1 and BRCA2 influence the expression of FANCD2 and influence ovarian cancer risk in selected families.

The majority of the patients participated in Gynecologic Oncology Group studies and the definitions of high-risk are congruent with Gynecologic Oncology Group guidelines. The pertinent personal and family histories of the high-risk patients we described (1) are presented in Table 1.

We emphasize that all women in our study had either a personal or family history of ovarian cancer. We used neither BRCA status nor breast cancer–only cases as indexing methods. The studies cited in support of the implication of Swisher and King that ovarian cancer families can be ruled out by BRCA1 and BRCA2 mutation analyses do not support their assertion. These studies ascertained patients based on breast cancer family history without regard to ovarian cancer history (2, 3), were based on a highly selected Ashkenazi-Jewish population (2), and were not sufficiently powered to conclude that there is no risk of ovarian cancer in “breast cancer–only” families with negative BRCA1 and BRCA2 testing (2). Not only are the studies too narrowly defined to support the broader claim but also no underpowered study can ever show a lack of risk. In summary, the cited studies cannot be legitimately used to conclude, as Swisher and King have done, that our on-study criteria would necessarily include women at “low future risk” of ovarian cancer.

The field of BRCA biochemistry is laden with studies on transformed cells and there are many studies reported using transformed cells from potentially irrelevant lineages. Uniquely important functions of these genes and genes like them must be validated in studies on primary cells from relevant tissues. The idea that “normal ovarian epithelial cells are not vigorous in culture, tolerating few passages before senescence” is no truer for ovarian cells than for other primary epithelial cell populations with which we have extensive experience. The approach we use is used in other centers involved in studies on primary ovarian epithelial cells, and we have successfully applied the same method to cultures of epithelial cells obtained from a variety of organs from humans and Fancd2 knockout mice. We passage such cells about nine times before they senesce. The mitomycin C assays were done on cells in passages one through five.

Contrary to the implications of Swisher and King, we did not claim to have ruled out all potential BRCA1 and BRCA2 mutations, have not suggested that women at risk should not seek genetic counseling (preoperative counseling was provided to all high-risk participants), and did not suggest that the methods we describe could be a screening tool, only that modifications of it might be. A number of centers are intrigued by mounting evidence that the Fanconi anemia pathway is involved in the molecular pathogenesis of epithelial malignancies. In light of observations that the BRCA1, BRCA2, and FANCD2 gene products participate in shared nuclear pathways and that Fancd2^−/− mice develop ovarian neoplasms, we hold the view that BRCA1 and BRCA2 do not constitute the whole of the ovarian cancer universe. We will continue to conduct studies designed to directly test the validity of this notion.