What is the role of serum CA 125 testing in monitoring response to treatment?

Updated: Jan 10, 2020
  • Author: Gentry George T King, MD; Chief Editor: Eric B Staros, MD  more...
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Declining CA 125 levels have been shown to correlate with treatment response, even when disease is not detectable with physical examination or imaging. In this setting, serial CA 125 testing has more clinical utility than a single determination.

The Gynecologic Cancer Intergroup (GCIG) defines a response to treatment as a reduction of 50% or more in pretreatment CA 125 levels maintained for at least 28 days. [8] The pretreatment value must be at least twice the upper limit of the reference range and taken 2 weeks prior to treatment. Subsequent samples are taken at weeks 2 and 4 of treatment and at intervals of 2-3 weeks thereafter. However, tumor recurrence may occur in the setting of normal CA 125 levels, and serum measurements do not replace imaging and physical examination of the patient. [8]

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