Volume 115, Issue 7 p. 1395-1403
Review Article
Free Access

CA-125 change after chemotherapy in prediction of treatment outcome among advanced mucinous and clear cell epithelial ovarian cancers

A Gynecologic Oncology Group study

Chunqiao Tian MS

Chunqiao Tian MS

Gynecologic Oncology Group Statistical and Data Center, Roswell Park Cancer Institute, Buffalo, New York

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Maurie Markman MD

Corresponding Author

Maurie Markman MD

Department of Gynecologic Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, Texas

Fax: (713) 563-9586

Department of Gynecologic Medical Oncology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030===Search for more papers by this author
Richard Zaino MD

Richard Zaino MD

M. S. Hershey Medical Center, Pennsylvania State University, Hershey, Pennsylvania

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Robert F. Ozols MD

Robert F. Ozols MD

Fox Chase Cancer Center, Philadelphia, Pennsylvania

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William P. McGuire MD

William P. McGuire MD

Harry and Jeanette Weinberg Cancer Institute, Franklin Square Hospital Center, Baltimore, Maryland

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Franco M. Muggia MD

Franco M. Muggia MD

Kaplan Cancer Center, New York University Medical Center, New York, New York

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Peter G. Rose MD

Peter G. Rose MD

Department of Obstetrics and Gynecology, Division of Gynecologic Oncology, Cleveland Clinic Foundation, Cleveland, Ohio

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David Spriggs MD

David Spriggs MD

Memorial Sloan-Kettering Cancer Center, New York, New York

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Deborah K. Armstrong MD

Deborah K. Armstrong MD

Johns Hopkins Kimmel Cancer Center, Baltimore, Maryland

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First published: 04 February 2009
Citations: 60

The following Gynecologic Oncology Group member institutions participated in the primary treatment studies: University of Alabama at Birmingham, Oregon Health Sciences University, Duke University Medical Center, Abington Memorial Hospital, University of Rochester Medical Center, Walter Reed Medical Center, Wayne State University, University of Minnesota Medical School, University of Southern California at Los Angeles, University of Mississippi Medical Center, Colorado Gynecologic Oncology Group, P.C., University of California at Los Angeles, University of Miami School of Medicine, Milton S. Hershey Medical Center, Georgetown University Hospital, University of Cincinnati, University of North Carolina School of Medicine, University of Iowa Hospitals and Clinics, University of Texas Southwestern Medical Center at Dallas, Indiana University Medical Center, Wake Forest University School of Medicine, Albany Medical Center, University of California Medical Center at Irvine, Tufts-New England Medical Center, Rush-Presbyterian-St. Luke's Medical Center, Stanford University Medical Center, SUNY Downstate Medical Center, University of Kentucky, Eastern Virginia Medical School, The Cleveland Clinic Foundation, Johns Hopkins Cancer Center, State University of New York at Stony Brook, Eastern Pennsylvania Gynecology/Oncology Center, P.C., Washington University School of Medicine, Cooper Hospital/University Medical Center, Columbus Cancer Council, M. D. Anderson Cancer Center, University of Massachusetts Medical School, Fox Chase Cancer Center, Medical University of South Carolina, Women's Cancer Center, University of Oklahoma.

Abstract

BACKGROUND:

There are limited data regarding unique clinical or laboratory features associated with advanced clear cell (CC) and mucinous (MU) epithelial ovarian cancers (EOC), particularly the relationship between CA-125 antigen levels and prognosis.

METHODS:

A retrospective review of 7 previously reported Gynecologic Oncology Group phase 3 trials in patients with stage III/IV EOC was conducted. A variety of clinical parameters were examined, including the impact of baseline and changes in the CA-125 level after treatment of CC and MU EOC on progression-free (PFS) and overall survival (OS).

RESULTS:

Clinical outcomes among patients with advanced CC and MU EOC were significantly worse when compared with other cell types (median PFS, 9.7 vs 7.0 vs 16.7 months, respectively, P < .001; median OS, 19.4 vs 11.3 vs 40.5 months, respectively, P < .001). Suboptimal debulking was associated with significantly decreased PFS and OS among both. Although baseline CA-125 values were lower in CC (median, 154 μ/mL) and MU (100 μ/mL), compared with other cell types (275 μ/mL), this level did not appear to influence outcome among these 2 specific subtypes of EOC. However, an elevated level of CA-125 at the end of chemotherapy was significantly associated with decreased PFS and OS (P < .01 for all).

CONCLUSIONS:

Surgical debulking status is the most important variable at prechemotherapy predictive of prognosis among advanced CC and MU EOC patients. Changes in the CA-125 levels at the end treatment as compared with baseline can serve as valid indicators of PFS and OS, and likely the degree of inherent chemosensitivity. Cancer 2009. © 2009 American Cancer Society.

The serum level of CA-125 is well established as a highly useful surrogate for monitoring the response to treatment and confirming relapse in women with epithelial ovarian cancer.1-4 However, the literature has focused on the more common ovarian cancer histologies, particularly the serous subtype.5-9

The prognostic value of CA-125 for clear cell or mucinous ovarian cancers is less certain. Both of these entities are rare in the advanced disease setting, together accounting for approximately 5% to 8% of all patients in clinical trials.10-18 Unfortunately, survival of these patients has been shown to be poor.17, 18 There are also reports that these 2 histologies are relatively resistant to cytotoxic chemotherapy,19-22 and that the CA-125 antigen may not be secreted in the mucinous cell type.23, 24 As a result of these unique clinical features, one may reasonably question whether this prognostic factor identified for the overall epithelial ovarian cancer population actually applies to these 2 cell types.17, 18, 25, 26

Studies on clear cell and mucinous ovarian cancers are difficult because of the limited numbers, and realistically require an analysis of the combined experience of several studies. To examine unique clinical features of advanced clear cell and mucinous epithelial ovarian cancers, with a particular focus on the predictive value of serum CA-125 antigen in these settings, a review was conducted of 7 Gynecologic Oncology Group (GOG) phase III clinical trials.10-16 Reported here are the results of that evaluation.

MATERIALS AND METHODS

The current study consisted of a review of data obtained from 7 completed and published phase 3 randomized trials conducted by the GOG (Protocols #111, #114, #132, #152, #158, #162, and #172) involving patients with advanced epithelial ovarian cancer. All cases were at International Federation of Gynecology and Obstetrics (FIGO) stage III or IV, without undergoing prior chemotherapy or radiation before enrollment in the trials; a majority of patients were treated by standard chemotherapy of 6 cycles of platinum/paclitaxel as required by protocols. Details regarding eligibility criteria, treatment, and outcome for each particular study have been previously published.10-16 All patients provided written informed consent consistent with federal, state, and local requirements before receiving protocol therapy.

The primary endpoints for all 7 studies were progression-free survival (PFS) and overall survival (OS). PFS was calculated from the date of study enrollment to the date of disease recurrence (confirmed on physical, radiologic, or serologic exam), death, or most recent follow-up visit. OS was calculated from the date of study enrollment to the date of death by any cause or last contact. The tumor cell type was determined by the individual institution, and all the pathologic materials were centrally reviewed and confirmed by the GOG Pathology Committee.

CA-125 data, which were assayed at each clinical laboratory, were collected at baseline and during treatment. The baseline CA-125 was determined before chemotherapy and after primary surgical cytoreduction. CA-125 obtained during treatment was measured at the beginning of each treatment cycle. For the present analysis, CA-125 at the end of primary chemotherapy was considered the last measurement of CA-125 level over the treatment period whenever the last measurement was performed.

The baseline patient characteristics evaluated included patient age, GOG performance status (PS), FIGO stage, surgical debulking status, and tumor grade. Patients were divided into 4 groups based on stage and debulking status: stage III optimal microscopic (no gross residual), stage III optimal gross (0.1-1.0 cm), stage III suboptimal (>1.0 cm), and stage IV. Clear cell carcinoma was considered “not graded” because there is no accepted standard grading system for this cell type. PS was defined according to GOG criteria as: 0 = normal activity; 1 = symptomatic, fully ambulatory; 2 = symptomatic, in bed less than 50% of the time. The type of chemotherapy was not considered in the analysis, because the majority (approximately 90%) of patients received platinum-based treatment.

Patient characteristics were compared among clear cell, mucinous, and other cell types using chi-square test for categorical variables (PS, stage/debulking, and tumor grade) and Kruskal-Wallis rank test for continuous variables (age and CA-125). The Kaplan-Meier procedure was used to estimate PFS and OS, and the group difference in survival function was compared using log-rank test. All the tests were to assess the null hypotheses that the patient characteristics and clinical outcomes were not different among clear cell, mucinous, and other cell types.

The Cox proportional hazards model was used to assess the association between the clinical and pathological factors, and disease progression and survival. In the multivariate analysis, patients with suboptimal stage III and stage IV were combined because of the small number of patients in the latter group. Likewise, GOG PS of 1 and 2 were combined, as were tumor grades 2 or 3. CA-125 was categorized as normal (≤35 μ/mL) or high (>35 μ/mL), consistent with the definition of CA-125 normalization commonly used in clinical practice. All statistical tests were 2-tailed. P < .05 was interpreted as statistically significant. All statistical analyses were performed using Statistical Analysis Software (SAS) version 9.1 (SAS Institute, Cary, NC).

RESULTS

One hundred nine (3%) patients with clear cell type and 73 (2%) with mucinous cell type were reviewed from a total of 3474 stage III/IV patients with epithelial ovarian cancer enrolled in the 7 GOG protocols. The baseline characteristics and clinical outcomes for women with the 2 histologies are summarized in Table 1, as compared with other cell types.

Table 1. Comparison of Clinical Characteristics and Outcomes for Advanced Stage Clear Cell and Mucinous Ovarian Cancers and Other Cell Types
Cell Type
Clear Cell (n=109) Mucinous (n=73) Others (n=3292) P*
Median age, y 54 52 58 <.001
GOG PS, % .65
 0 37 41 38
 1 53 53 51
 2 10 6 11
Stage/debulking, % <.001
 III-optimal micro 39 27 16
 III-optimal gross 21 21 32
 III-suboptimal 27 34 35
 IV 13 18 17
Tumor grade, % Not graded <.001
 1 51 8
 2 38 38
 3 11 53
Median CA-125, μ/mL 154 100 275 <.001
Median PFS, mo 9.7 7.0 16.7 <.001
Median OS, mo 19.4 11.3 40.5 <.001
  • GOG indicates Gynecologic Oncology Group; PS, performance status; PFS, progression-free survival; OS, overall survival.
  • * P value is reported as global test of comparison among three groups.
  • III-optimal micro: stage III without gross tumor residual after debulking; III-optimal gross: stage III with a tumor residual >0 and ≤1 cm after debulking; III-suboptimal: stage III with a tumor residual >1 cm after debulking.
  • CA-125 data available for 101 patients with clear cell, 66 with mucinous, and 1695 with other cell types.

Clear cell or mucinous ovarian cancer patients were unique in several features: 1) they were more often diagnosed at earlier age (median age: 54 years for clear cell, 52 years for mucinous vs 58 years for other cell types); 2) well-differentiated tumor (grade 1) was frequently observed among the mucinous type (51% for mucinous vs 8% for other cell types); 3) complete resection (without gross disease residual) was more frequently accomplished (39% for clear cell and 27% for mucinous vs 16% for other cell types); 4) CA-125 level (measured at prechemotherapy after surgical debulking) was significantly lower, particularly among the mucinous type (median level: 154 μ/mL for clear cell and 100 μ/mL for mucinous vs 275 μ/mL for other cell types; elevated CA-125: 87% vs 74% vs 93%); and 5) both clear cell and mucinous patients experienced substantially poorer outcomes compared with other cell types. The median PFS was 9.7 months for clear cell, 7.0 months for mucinous, and 16.7 months for other cell types, whereas the median OS was 19.4 months, 11.3 months, and 40.5 months, respectively. Sixty-one percent of clear cell patients had disease recurrence, and 34% died during the first year of study. The prognosis of mucinous patients was even worse, with 64% showing disease progression and 52% dying by the end of the first year of follow-up, in contrast to other cell types with 33% having disease progression and only 11% dying within the first year of treatment. The survival after disease recurrence was 7.6 months, 4.1 months, and 19.0 months, respectively, for clear cell, mucinous, and other cell types.

The prognostic value of pretreatment CA-125 for ovarian cancer derived from patients based on standard cisplatin/paclitaxel has been reported elsewhere.27 That analysis included only 37 clear cell and 26 mucinous cell patients. The present analysis involved more patients treated with platinum-based chemotherapy and focused on assessment of the prognostic value of CA-125 change after treatment among clear cell and mucinous ovarian cancers.

Clear Cell Ovarian Cancer

The most common patient characteristics (age, PS, and stage/debulking status) associated with clinical outcomes were assessed first using the Cox regression model. The stage/debulking status were significantly predictive of prognoses. Compared with the stage III/microscopic patients, women with suboptimal stage III or stage IV were at increased risk for disease progression (hazard ratio [HR], 3.50; 95% confidence interval [CI], 2.13-5.75) and increased risk for death (HR, 2.71; 95% CI, 1.61-4.57). The prognostic values of age with OS (HR: 1.28, 95% CI, 1.03-1.58 for increase of each 10 years) and PS with PFS (HR: 1.50, 95% CI, 0.95-2.37, for PS 1 or PS 2 vs PS 0) were also suggestive (Table 2).

Table 2. Multivariate Analyses of Prognostic Factors for Advanced Stage Clear Cell Ovarian Cancer
Disease Progression Death
HR 95% CI P HR 95% CI P
Age (increase 10 y) 1.13 0.93-1.38 .23 1.28 1.03-1.58 .03
GOG PS .08 .67
 0 1.0 1.0
 1 or 2 1.50 0.95-2.37 1.11 0.68-1.82
Stage/debulking* <.001 <.001
 III-optimal micro 1.0 1.0
 III-optimal gross 1.25 0.70-2.24 1.43 0.77-2.65
 III-suboptimal/IV 3.50 2.13-5.75 2.71 1.61-4.57
  • HR indicates hazard ratio estimated from Cox model; CI, confidence interval; GOG, Gynecologic Oncology Group; PS, performance status.
  • * III-optimal micro: stage III without gross tumor residual after debulking; III-optimal gross: stage III with a tumor residual >0 and ≤1 cm after debulking; III-suboptimal: stage III with a tumor residual >1 cm after debulking.

Prechemotherapy CA-125 was available for 101 patients. The median level was 154 μ/mL, and 13% of patients had a level ≤35 μ/mL. The baseline CA-125 level was associated with residual tumor. The median CA-125 was 98, 154, and 225 μ/mL, respectively, for stage III-microscopic, stage III optimal, and stage III suboptimal plus stage IV patients. Seventy-seven patients had CA-125 data recorded during the course of treatment. The median level of CA-125 at the end of chemotherapy was 21 μ/mL, and 65% of individuals achieved a level ≤35 μ/mL. In responding patients, the CA-125 antigen decreased with each treatment cycle, with a steep reduction after the first course.

The prognostic value of CA-125 at baseline or during treatment was evaluated separately. The relative risk for disease progression or death for patients >35 μ/mL (high) versus ≤35 μ/mL (normal) was estimated and adjusted for stage/debulking status, age, and PS. As shown in Table 3, there is a suggestion that CA-125 at baseline was associated with the clinical outcomes (HR, 1.95; 95% CI, 0.84-5.54 for disease progression; and HR, 1.42; 95% CI, 0.57-3.53 for death), although it did not reach the level of being statistically significant. However, there is strong evidence that the CA-125 level at the end of treatment was independently predictive of both disease progression (HR, 3.34; 95% CI, 1.96-5.68) and death (HR, 2.41; 95% CI, 1.39-4.19). The estimate of cumulative distribution of PFS based on CA-125 change is illustrated in Figure 1.

Details are in the caption following the image

Kaplan-Meier estimate of progression-free survival (PFS) by comparing CA-125 levels at prechemotherapy and at the end of chemotherapy for advanced stage clear cell ovarian cancer. Normal-normal indicates CA-125 ≤35 μ/mL at both pre- and end of chemotherapy; High-normal, CA-125 reduction from >35 μ/mL at prechemotherapy to ≤35 μ/mL at the end of chemotherapy; High-high, CA-125 >35 μ/mL at both pre- and end of chemotherapy; NPG, no disease progression; PG, disease progression. One patient showing change from ≤35 μ/mL to >35 μ/mL was not included for the survival estimate.

Table 3. CA-125 Levels and Clinical Outcomes for Advanced Stage Clear Cell Ovarian Cancer
Disease Progression Death
High vs Normal CA-125 HR 95% CI P HR 95% CI P
At pretreatment 1.95 0.84-4.54 .12 1.42 0.57-3.53 .45
At end of treatment 3.34 1.96-5.68 <.001 2.41 1.39-4.19 .002
  • HR indicates hazard ratio; CI, confidence interval.
  • CA-125 at prechemotherapy or during treatment was evaluated separately by Cox regression models. Estimated HR was adjusted for age, performance status, and International Federation of Gynecology and Obstetrics stage/volume residual. CA-125 at pretreatment was defined as the measurement at prechemotherapy after surgical debulking. CA-125 at the end of treatment was defined as the last measurement of CA-125 level over the treatment period. CA-125 ≤35 μ/mL was defined as normal, and CA-125 >35 μ/mL was defined as high.

Mucinous Ovarian Cancer

Similarly, the relationships of age, PS, stage/debulking status, and tumor grade with clinical outcomes were assessed for patients with mucinous ovarian cancer. Consistent with the data for clear cell type, the stage/debulking status was the most important factor associated with prognoses. Patients with suboptimal stage III or stage IV had a relative risk of 2.28 (95% CI, 1.25-4.15) for disease progression and a relative risk of 2.08 (95% CI, 1.14-3.78) for death compared with stage III/microscopic patients. In contrast to clear cell patients, the association of age with clinical outcome for mucinous patients was not statistically significant. Furthermore, there is no evidence that tumor grade was predictive of either PFS (HR, 1.05; 95% CI, 0.64-1.72 for grade 2 of 3 vs grade 1) or OS (HR, 1.09; 95% CI, 0.66-1.79) (Table 4).

Table 4. Multivariate Analyses of Prognostic Factors for Advanced Stage Mucinous Ovarian Cancer
Disease Progression Death
HR 95% CI P HR 95% CI P
Age (increase 10 y) 1.14 0.96-1.36 .15 1.10 0.92-1.31 .30
GOG PS .22 .35
 0 1.0 1.0
 1 or 2 1.37 0.83-2.27 1.28 0.77-2.12
Stage/debulking* .03 .05
 III-optimal micro 1.0 1.0
 III-optimal gross 1.60 0.78-3.31 1.35 0.65-2.82
 III-suboptimal/IV 2.28 1.25-4.15 2.08 1.14-3.78
Tumor grade .84 .74
 1 1.0 1.0
 2 or 3 1.05 0.64-1.72 1.09 0.66-1.79
  • HR indicates hazard ratio estimated from Cox model; CI, confidence interval; GOG, Gynecologic Oncology Group; PS, performance status.
  • * III-optimal micro: stage III without gross tumor residual after debulking; III-optimal gross: stage III with a tumor residual >0 and ≤1 cm after debulking; III-suboptimal: stage III with a tumor residual >1 cm after debulking.

Sixty-six patients had baseline CA-125 data. The median level was 100 μ/mL (48, 47, and 154 μ/mL, respectively, for stage III-microscopic, stage III optimal, and stage III suboptimal plus stage IV), with 26% of patients having a prechemotherapy level ≤35 μ/mL. The CA-125 data at the end of chemotherapy was available for 50 patients, with a median level of 24 μ/mL and 62% of individuals having a level ≤35 μ/mL.

After adjusting for stage/debulking status, age, and PS, the CA-125 level at baseline was not significantly related to PFS (HR, 1.23; 95% CI, 0.65-2.34), although it showed a trend toward significance with OS (HR, 1.68; 95% CI, 0.89-3.17). However, in contrast to the prechemotherapy CA-125, the CA-125 level at the end of treatment was highly associated with both PFS (HR, 5.08; 95% CI, 2.40-10.75) and OS (HR, 2.25; 95% CI, 1.91-5.52) (Table 5). The estimate of PFS, based on CA-125 change from baseline determination to the end of chemotherapy, is shown in Figure 2. The normal-to-normal (≤35 μ/mL at both time points) and high-to-normal (CA-125 reduced to ≤35 at the end of treatment from >35 μ/mL at pretreatment) groups demonstrated similar PFS, whereas the high-to-high (>35 μ/mL at 2 time points) patients experienced a much shorter PFS. The data indicate that CA-125 regressing to normal during chemotherapy is a sensitive and significant factor associated with a more favorable prognosis for mucinous epithelial ovarian cancer.

Details are in the caption following the image

Kaplan-Meier estimate of progression-free survival (PFS) by comparing CA-125 level at prechemotherapy and the end of chemotherapy for advanced stage mucinous ovarian cancer. Normal-normal, CA-125 ≤35 μ/mL at both pre- and end of chemotherapy; High-normal, CA-125 reduction from >35 μ/mL at prechemotherapy to ≤35 μ/mL at the end of chemotherapy; High-high, CA-125 >35 μ/mL at both pre- and end of chemotherapy; NPG, no disease progression; PG, disease progression. Two patients showing change from ≤35 μ/mL to >35 μ/mL were not included for the survival estimate.

Table 5. CA-125 Levels and Clinical Outcomes for Advanced Stage Mucinous Ovarian Cancer
Disease Progression Death
High vs Normal CA-125 HR 95% CI P HR 95% CI P
At pretreatment 1.23 0.65-2.34 .53 1.68 0.89-3.17 .11
At end of treatment 5.08 2.40-10.75 <.001 2.25 1.91-5.52 <.001
  • HR indicates hazard ratio; CI, confidence interval.
  • CA-125 at prechemotherapy or during treatment was evaluated separately by Cox regression models. Estimated HR was adjusted for age, performance status, and International Federation of Gynecology and Obstetrics stage/volume residual. CA-125 at pretreatment was defined as the measurement at prechemotherapy after surgical debulking. CA-125 at end of treatment was defined as the last measurement of CA-125 level over the treatment period. CA-125 ≤35 μ/mL was defined as normal, and CA-125 >35 μ/mL was defined as high.

In summary, stage and tumor residual were the most important prognostic factors for both clear cell and mucinous epithelial ovarian cancer patients; age was only associated with OS for clear cell patients; neither tumor grade nor performance status was significantly associated with clinical outcome; CA-125 at pretreatment was less significant in prediction of prognosis; and CA-125 after treatment was a valid indicator for monitoring treatment effect among these 2 specific cell types.

DISCUSSION

This examination of 7 large multi-institutional phase 3 GOG trials that included advanced clear cell and mucinous ovarian cancers has confirmed both the rarity of these histologic types (combined 5% incidence in the 7 studies involving more than 3000 total patients), and the poor prognosis associated with these entities.17-22

As known for other cell types, the stage of disease and the amount of residual cancer are the 2 most important prognostic factors for patients presenting with either an advanced clear cell or mucinous ovarian cancer. Of interest, in this series, patients with both of these histologies were younger at presentation, compared with the other cell types. Also striking was the lack of association between tumor grade and survival in mucinous ovarian cancer.

A higher percentage of advanced stage mucinous and clear cell ovarian cancers were surgically cytoreduced to microscopic disease, compared with other cell types. Despite this observation, these patients experienced a substantially inferior overall outcome. This fact reinforces the concept of the relative chemoresistance of both clinical entities.19-22

Data regarding the serum CA-125 levels for patients presenting with advanced clear cell and mucinous ovarian cancers, and their relationship to survival, are also revealing. In both entities, the baseline (prechemotherapy) CA-125 antigen levels are lower than other cell types, with median values for clear cell and mucinous cancers being approximately ½ and ⅓, respectively, compared with all other epithelial ovarian histologies. This observation may result both from the apparent initial smaller volume of disease present after primary surgical cytoreduction as well as from fundamental differences in the biology of the malignancies.

However, of particular note, although the baseline CA-125 determinations were less significant in prediction of clinical outcomes, CA-125 regressing to a normal level after treatment was significantly associated with improved PFS and OS in clear cell and mucinous ovarian cancers. This subgroup of patients, representing approximately 50% of either clear cell or mucinous ovarian cancers, was more likely to benefit from treatment.

Our data also suggest that currently available platinum-based chemotherapy appears to be of only modest benefit in both advanced clear cell and mucinous ovarian cancers as compared with serous and other cell types, although some patients with these histologies and some degree of drug sensitivity may experience a meaningful degree of benefit from such therapy. It is relevant to note that survival in these populations, although generally quite poor, might be considerably worse in the absence of the delivery of platinum-based chemotherapy. New treatment approaches are urgently required in both advanced clear cell and mucinous ovarian cancers.

Although the number of clear cell (n = 109) or mucinous cell type (n = 73) patients included in the present study is still limited, it is 1 of the largest studies on advanced clear cell and mucinous epithelial ovarian cancers thus far. All the data were based on phase III clinical trials. Patients received standard surgical treatments, and clinical information (clinical parameters, CA-125, and outcomes) were prospectively collected in a rigorous manner, although the analysis was done retrospectively. Our data would provide reliable information for understanding these 2 rare cell types of epithelial ovarian cancer at an advanced setting.

Acknowledgements

We thank Mark Brady PhD, for critical review of the article and providing helpful suggestions, and Anne Reardon for assistance in preparing this article for publication.

    Conflict of Interest Disclosures

    This study was supported by National Cancer Institute grants CA 27,469 (Gynecologic Oncology Group) and CA 37,517 (Gynecologic Oncology Group Statistical and Data Center).