Utility of serum CA-125 monitoring in patients with ovarian cancer undergoing immune checkpoint inhibitor therapy

Gynecol Oncol. 2020 Aug;158(2):303-308. doi: 10.1016/j.ygyno.2020.04.710. Epub 2020 Jun 2.


Objective: This study aimed to evaluate the utility of serum cancer antigen-125 (CA-125) levels to monitor patients with epithelial ovarian cancer (EOC) undergoing immune checkpoint inhibitor (ICI) therapy.

Method: This was a single-center retrospective review of all patients with EOC who were treated with ICI therapy from January 2013 to May 2017. This study compared the percentage change in baseline CA-125 in patients who had clinical benefit, defined as complete response, partial response, or stable disease by RECIST 1.1, with duration ≥24 weeks, versus those who did not. The groups were compared by Wilcoxon rank-sum test.

Results: Fifty-nine (66%) of 89 patients who underwent ICI therapy had CA-125 data at baseline and during treatment. Of those who derived clinical benefit, 11/15 (73%) experienced an increase in CA-125 from baseline to end of treatment. Of those who did not derive clinical benefit, 36/44 (82%) experienced a CA-125 increase (p = 0.48). The average % increase from baseline to within 12 weeks of treatment initiation for patients with and without clinical benefit was 34% and 195%, respectively (p = 0.008).

Conclusion: Our analysis demonstrates a statistically significant difference in the magnitude of increase in CA-125 levels within the first 12 weeks of treatment between patients who achieved clinical benefit and those who did not. However, both groups of patients were equally likely to experience an increase in CA-125 within 12 weeks. These findings suggest that physicians should apply caution when using early CA-125 data to guide treatment decisions for patients with EOC undergoing ICI therapy.

Keywords: CA-125; Checkpoint inhibition; Immunotherapy; Ovarian cancer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adult
  • Aged
  • CA-125 Antigen / blood*
  • Carcinoma, Ovarian Epithelial / blood*
  • Carcinoma, Ovarian Epithelial / drug therapy*
  • Cohort Studies
  • Female
  • Humans
  • Immune Checkpoint Inhibitors / administration & dosage*
  • Membrane Proteins / blood*
  • Middle Aged
  • Ovarian Neoplasms / blood*
  • Ovarian Neoplasms / drug therapy*
  • Retrospective Studies


  • CA-125 Antigen
  • Immune Checkpoint Inhibitors
  • MUC16 protein, human
  • Membrane Proteins