Screening for ovarian cancer: what are the optimal surrogate endpoints for clinical trials?

Comprehensive profiling of EGFR/HER receptors for personalized treatment of gynecologic cancers

The primary gynecologic cancers include cancers of the endometrium, ovary, and cervix. Worldwide, cervical cancer is the most common gynecologic cancer, whereas endometrial cancer is the most common in the US. Ovarian cancer is the fifth most deadly cancer in women, with 5-year survival rates for advanced disease at only 27 %. As such, there is an urgent need for reliable screening tools and novel targeted therapeutic regimens for these malignancies. The epidermal growth factor receptor (EGFR)/human EGFR (HER) family of receptors has been associated with the development and progression of many solid tumors. Despite clear roles for these receptors in other cancers, the expression of HER family members in gynecologic cancers and their relationship with disease stage, grade, and response to treatment remain controversial. In this review, we describe the existing evidence for the use of HER family members as diagnostic and prognostic indicators as well as their potential as therapeutic targets in gynecologic cancers.

Soluble Epidermal Growth Factor Receptor (SEG-FR) and Cancer Antigen 125 (CA125) as Screening and Diagnostic Tests for Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the leading cause of death among all gynecologic cancers in the United States. Because women who are diagnosed with early stage disease have a better prognosis than women diagnosed with late stage disease, early detection represents a potentially practical approach to reduce the mortality associated with EOC. Unfortunately, no single screening test has proven to be effective for this purpose, and a valid and feasible screening program to detect early stage EOC in the general population has not yet been devised. Consequently, research has focused on coupling two or more screening modalities to improve program validity and feasibility. Serum cancer antigen 125 (CA125) and a soluble isoform of the epidermal growth factor receptor (p110 sEGFR) have been studied individually as biomarkers of ovarian cancer. In this study, we compare serum CA125 levels and sEGFR concentrations in women with EOC to women with benign gynecologic conditions of ovarian and non-ovarian origin. We show that serum sEGFR concentrations are lower in patients with EOC than in women with benign gynecologic conditions, whereas serum CA125 levels are higher in patients to EOC compared with women with benign gynecologic conditions. These data also reveal that age and serum sEGFR concentrations modify the association between CA125 levels and EOC versus benign gynecologic disease. Hence, age- and sEGFR-dependent CA125 cutoff thresholds improve the ability of CA125 to discern EOC patients from women with benign ovarian tumors and non-ovarian gynecologic conditions. Our analyses show that parallel testing with fixed sEGFR and CA125 cutoff thresholds optimizes sensitivity to detect EOC, whereas serial testing with age- and sEGFR-dependent CA125 cutoff thresholds optimizes test specificity, and overall accuracy to discern patients with EOC from women with benign ovarian and non-ovarian gynecologic conditions. The combined use of serologic sEGFR and CA125, thus, has improved utility for screening and diagnosing EOC, which may increase the positive predictive value of a multimodal screening program that incorporates these biomarkers to detect and subsequently differentiate benign from malignant ovarian tumors.

Cell-free 27 kDa heat shock protein (hsp27) and hsp27-cytochrome c complexes in the cervix of women with ovarian or endometrial cancer

Antibodies to the 27 kDa heat shock protein (hsp27) are present in some women with ovarian and endometrial cancers but not in women with nonmalignant conditions or healthy women. The appearance of these antibodies suggests that the corresponding protein (hsp27) may be present in an extracellular form in gynecologic cancer patients. Synthesis of hsp27 is upregulated in gynecologic cancers and inhibits induction of apoptosis. We now report the detection of hsp27 as well as hsp27-cytochrome c complexes in cell-free endocervical or posterior vaginal specimens from women with endometrial or ovarian cancer. Specimens were obtained with a cotton swab from 209 consecutive patients seen by a gynecologic oncologist. After removal of cellular components, aliquots of supernatants were assayed by ELISA for hsp27, using cytochrome c bound to microtiter plate wells, and for hsp27-cytochrome c complexes, using antibodies to cytochrome c and hsp27. Among 47 women with ovarian cancer, 38.3% were positive for hsp27 and 27.7% had hsp27-cytochrome c complexes. Similarly, among 52 women with endometrial cancer, 34.6% were hsp27-positive and 30.8% had hsp27-cytochrome c complexes. In contrast to the women with ovarian or endometrial cancer, of the 86 women with benign diagnoses only, 10.5% had cervical hsp27 (p < 0.002) and 8.1% had hsp27-cytochrome c complexes (p < 0.004). Among ovarian cancer patients, hsp27 was identified in 44.0% of the 25 women with active disease as opposed to 17.6% of the 17 patients in remission (p < 0.05). In women with stage 1-2 active ovarian cancer, 8 of 10 (80.0%) were hsp27-positive as opposed to 3 of 14 (21.4%) stage 3-4 patients (p < 0.01). For hsp27-cytochrome c complexes, 50% of ovarian cancer patients with active stage 1-2 disease as opposed to 21.4% with stage 3-4 disease were positive. Among women with endometrial cancer, only 10 of the 52 patients had active disease and 44 were in stage 1-2. For this malignancy, there was no relation between detection of hsp27 or hsp27-cytochrome c and active disease or cancer stage. Our results suggest that cell-free hsp27 and hsp27-cytochrome c complexes can be detected in the lower genital tract of women with ovarian and endometrial cancers. Identification of these biomarkers may be beneficial in the early diagnosis of these malignancies.

The promise and peril of surrogate end points in cancer research

Both experimental and observational studies of cancer need to have an end point. Traditionally, in aetiological and prevention studies, that end point has been the incidence of cancer itself, whereas in therapeutic trials, the end point is usually time to cancer recurrence or death. But cancer takes a long time to develop in an individual and is rare in the population. Therefore, aetiological studies and prevention trials must be large and lengthy to be meaningful. Similarly, many therapeutic trials require a long follow-up of large numbers of patients. Surrogate end points--markers of preclinical cancer or of imminent recurrence--are therefore an attractive alternative. But how can we be sure that a study with a surrogate outcome gives us the right answer about the true end point?

Intermediate markers as surrogate endpoints in cancer research

Because studies with surrogate cancer endpoints can be smaller, faster, and substantially less expensive than those with frank cancer outcomes, the use of surrogate endpoints is undeniably attractive. This attractiveness is likely to grow in coming years as the rapidly advancing discoveries in cell and molecular biology generate new therapies requiring testing and new markers that could plausibly serve as surrogates for cancer. Surrogate endpoint studies can certainly be suggestive. They continue to play a legitimate role in phase II studies, and they may give the right answers about intervention effects on or exposure associations with cancer. The problem is the uncertainty attached to most potential surrogates. Except for those few surrogates that are both necessary for and developmentally relatively close to cancer, the existence of plausible alternative pathways makes inferences about cancer from many surrogates problematic. Merely being on the causal pathway to cancer does not in itself constitute surrogate validity. It is the totality of causal connections that is critical. There is, unfortunately, a fairly extensive history of quite plausible surrogate markers giving the wrong answer about various chronic disease therapies. There is no reason to believe that cancer surrogacy is immune to such inferential difficulties. This article is, in part, an invitation, even a plea, for researchers to carry out the investigations necessary to evaluate potential surrogates, particularly surrogate-cancer studies and intervention or exposure-surrogate-cancer mediation analyses. Such studies are needed to generalize from surrogate endpoint findings to cancer. There is, however, an implicit and perhaps unavoidable irony here: the large, long, expensive studies required to evaluate potential surrogates fully are precisely the studies that surrogates were designed to replace. The exposure dependence alluded to earlier complicates matters further: establishing validity for a given surrogate for one intervention or exposure vis-à-vis cancer does not necessarily translate into validity for another intervention or exposure. One can enhance the inferential strength of surrogacy by using further "downstream" markers. Results of trials with CIN3 as an endpoint are arguably more persuasive than those from intervention studies with HPV infection endpoints. Similarly, one could consider only the advanced adenoma (> or = 1 cm, villous elements, or high-grade dysplasia) as the primary endpoint in adenoma recurrence trials. The inferential gain, however, comes with substantial costs: studies with CIN3 endpoints must be much larger than those with HPV infection endpoints; adenoma recurrence trials with sufficient rates of recurrence of advanced adenomas must be five or six times larger than trials with any recurrent adenomas as endpoints. A law emerges here: in using surrogate endpoints, inferential certainty is directly associated with study cost. In other words, one gets what one pays for. The problems inherent in using surrogate endpoints need not be regarded as a cause for pessimism in cancer research. If anything, the limitations of surrogacy are reminders of the complexity of cancer causation and affirm the continued importance of large clinical trials and observational epidemiologic studies with explicit cancer endpoints.

Peritoneal serous papillary carcinoma, a phenotypic variant of familial ovarian cancer: implications for ovarian cancer screening

OBJECTIVE

Our purpose was to report the cancers arising during a familial ovarian cancer screening program and investigate the tumor's clonality and association with BRCA1 and BRCA2 mutations.

STUDY DESIGN

Program participants with a diagnosis of ovarian cancer or peritoneal serous papillary carcinoma were identified and their demographic characteristics, ultrasonographic findings, CA 125 results, operative reports, and pathology slides reviewed. Immunohistochemical analysis of p53, bcl-2, HER-2/neu, and nm23 H1 expression was performed on tumor tissues from multiple metastatic sites, and germline BRCA1 and BRCA2 mutations were identified.

RESULTS

Three stage I ovarian cancers and 7 cases of peritoneal serous papillary carcinoma were diagnosed from among 1261 program participants. Ultrasonographic abnormalities triggered surgical exploration in all 3 cases of stage I disease. Elevated levels of CA 125 were the harbinger in 2 of 7 cases of peritoneal serous papillary carcinoma, abnormal ultrasonographic findings prompted diagnosis in 2 of 7 cases, and 3 of 7 women had abdominal symptoms 5, 6, and 16 months after screening. Results of immunohistochemical studies suggested multifocal disease in 5 of 7 patients with peritoneal serous papillary carcinoma. At least 3 of the patients with peritoneal serous papillary carcinoma carry BRCA1 185delAG mutations.

CONCLUSION

Multifocal peritoneal serous papillary carcinoma may be a phenotypic variant of familial ovarian cancer, and screening strategies for these women cannot rely on ultrasonography and CA 125 testing to detect early disease.

The status of ultrasound and color Doppler imaging for the early detection of ovarian carcinoma

Noninvasive imaging techniques such as ultrasound and color doppler imaging have been evaluated during the last decade for their ability to detect organ-confined curable ovarian cancer. While sensitivities approaching 100% can be achieved by these techniques, their specificities and the frequent invasive procedures required to confirm the abnormal sonographic findings have led to caution regarding the widespread use of ultrasound screening for ovarian cancer. These data are reviewed, as well as the NIH Consensus Panel on ovarian cancer's recommendation that routine screening for ovarian carcinoma should not be carried out at this time. Hereditary ovarian cancer syndromes account for approximately 5-10% of the cases. Many of the genes responsible for these syndromes have recently been elucidated. Due to the significant increase in the risk of ovarian cancer in these families, many screening studies have focused on this patient population. Findings from these trials, as well as studies on the psychological impact of screening are presented.