Results of a small, retrospective study showed a significant difference in the percentage increase in the serum level of cancer antigen-125 (CA-125) from baseline to 12 weeks following initiation of immune checkpoint therapy (ICI) in patients with recurrent/advanced epithelial ovarian cancer achieving clinical benefit compared with those who did not. These findings were published in Gynecologic Oncology.

Immune checkpoint inhibitor (ICI) therapy has been shown to have limited overall efficacy in the setting of recurrent/advanced epithelial ovarian cancer, although some patients have achieved long-term benefit from this treatment approach. Hence, there is a need for early biomarkers to facilitate the identification of patients who are likely to benefit from continuation of ICI therapy.

Because the use of serum levels of the CA-125 tumor marker, in conjunction with radiographic imaging and patient clinical status, has been shown to have clinical utility in assessing response to standard chemotherapy in the setting of recurrent ovarian cancer, the purpose of this study was to evaluate whether serum levels of CA-125 could also be used as a predictive biomarker for patients treated with ICI therapy.  

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This analysis was based on clinicopathologic data for patients with advanced/recurrent epithelial ovarian cancer treated at Memorial Sloan Kettering Cancer Center in New York, New York, with either single-agent or combination ICI therapy, including inhibitors of programmed cell-1 (PD-1), programmed cell death-ligand 1 (PD-L1), cytotoxic T lymphocyte activation-4 (CTLA-4), and lymphocyte activation gene-3 (LAG-3) between January 2013 and May 2017.

Study inclusion criteria included a baseline serum CA-125 measurement within 6 weeks prior to initiation of ICI therapy, as well as at least 2 serum CA-125 measurements between 6 weeks before treatment initiation and 1 week following cessation of ICI therapy. Patients treated with chemotherapy in combination with ICI therapy were excluded from the analysis. Response to ICI therapy was assessed using computed tomography imaging and RECIST 1.1 criteria.

Study endpoints included the percentage change in serum CA-125 level from baseline to end of ICI treatment and from baseline to 12 weeks of ICI therapy (or as close as possible to these time points) for those achieving clinical benefit, defined as complete response, partial response, or stable disease by RECIST 1.1 with duration of 24 weeks or longer, versus not.

Of the 59 patients included in this study, 15 (25%) achieved clinical benefit from ICI therapy, whereas 44 (75%) did not. In the former group, 73% of patients showed an increase in serum CA-125 from baseline to end of treatment, However, an elevated serum CA-125 level was also observed for 82% of patients not achieving clinical benefit from ICI therapy (P =.48). However, the percentage increase in serum CA-125 level between baseline and 12 weeks of treatment was 34% and 195% for those experiencing a benefit from ICI therapy compared with those without an ICI therapy benefit, respectively (P =.008).

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Regarding the latter finding, the study authors noted that “specific cutoffs could be potentially implemented to identify the patients who are less likely to benefit.”

Limitations of this study mentioned by the study authors included the small sample size, the diversity of ICI therapy received by these patients, as well as “the lack of uniform timing” with respect to serum CA-125 measurements.

In their concluding comments, the study authors noted that “these findings suggest that physicians should apply caution when using early CA-125 data to guide treatment decisions for patients with [epithelial ovarian cancer] undergoing ICI therapy.”


Boland JL, Zhou Q, Iasonos AE, et al. Utility of serum CA-125 monitoring in patients with ovarian cancer undergoing immune checkpoint inhibitor therapy. Gynecol Oncol [published online June 2, 2020].doi: 10.1016/j.ygyno.2020.04.710