Pre-treatment CA-125

Lots of recent conversations on CA-125. Some of us (me included) had normal CA-125s before the start of chemo. It doesn't necessarily mean CA-125 is inaccurate for you, and it may be a good sign.


Ovarian Cancer Marker Shows Prognostic Value
Wednesday, March 07, 2007



By Michael Smith
Senior Staff Writer, MedPage Today

Low levels of the tumor marker CA-125 -- measured before adjuvant chemotherapy for epithelial ovarian cancer -- appear to predict a longer time before the cancer recurs, researchers say.

CA-125 -- the tumor marker most closely associated with ovarian cancer -- is commonly used to measure response to chemotherapy, according to Kristin Zorn, MD, a gynecologic oncologist with Magee-Womens Hospital of UPMC.

But a pooled analysis of seven large phase III trials shows that pre-treatment serum CA-125 may also have a prognostic value, Dr. Zorn told a plenary session of the Society of Gynecologic Oncologists meeting in San Diego, Calif.

Indeed, at the highest level of more than 1,000 U/mL of serum, the risk of progression was 71% higher for any given interval than for the normal level of 35 U/ml, which was statistically significant, Dr. Zorn said. Several intermediate levels were also associated with significantly elevate risk.

Dr. Zorn and colleagues analyzed data from seven studies conducted by the Gynecologic Oncology Group, in which the adjuvant treatment arm consisted of a standard regimen of intravenous cisplatin and paclitaxel, after surgical debulking. Patients in the studies had stage III or IV disease.

All told, Dr. Zorn said, the analysis included 1,299 patients for whom a pre-treatment CA-125 value was available.

The researchers found:


The median pretreatment CA-125 level was 246 U/ml.
7.6% of patients had a normal level of less than 35 U/ml and 20% had a level above 1,000 U/ml.
The lowest median CA-125 levels were observed in the mucinous subtype (99 U/ml) and in patients with stage III disease that had only microscopic residual disease (117 U/ml).
65% of patients with a normal CA-125 level had serous tumors, or about 7% of all patients with serous tumors, which is the most common form of epithelial ovarian cancer.
On the other hand, 31% of patients with a mucinous tumor had normal CA-125.
The study also showed that a doubling of the pre-treatment level of CA-125 was associated with a 9% increase in the risk of progression, which was significant at P<0.0001.

But the study was unable to assess reliably the prognostic value of a normal CA-125 level before treatment, Dr. Zorn said, because only 99 of the 1,299 patients in the analysis had such a value.

That in itself is an interesting finding, she said later, because most authorities would suggest that between 10% and 20% of women with ovarian cancer have a normal CA-125 measurement before treatment.

Many experts would also suggest that a normal CA-125 level would indicate that the tumor is of mucinous sub-type, but that's not so, she said -- as in the population in general, those with a normal CA-125 are likely to have a serous tumor.

The study shows that "a single pre-treatment CA-125 value can provide valuable information regarding survival for patients with ovarian cancer," said Angeles Secord, M.D., of Duke University Medical Center in Durham, NC.

The study's strengths includes large numbers, prospective data collection and uniform treatment arms, Dr. Secord said, the design of the seven trials means the data can be generalized outside the study setting.

On the other hand, she said, the study is a meta-analysis, which raises the statistical problem of heterogeneity, since there was no central lab to conduct the CA-125 measurements, and there were a limited number of patients with various rare subtypes.

Dr. Zorn said the findings are "reassuring" in that they suggest that a low pre-treatment CA-125 level is probably a good sign even if the small numbers made it impossible to demonstrate definitively.

Because of the difficulty of performing randomized trials, "this is the best data we're ever going to have on this group of patients," she said.

Dr. Zorn's abstract — "Significance of Pretreatment CA-125 Level in Advanced Ovarian Carcinoma: A Meta Analysis of Seven Gynecologic Oncology Group Protocols" — was published in the 2007 edition of Gynecologic Oncology.



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