Rising CA-125 (Cancer Antigen 125) Levels: Cancer Recurrence or a Vaccine Reaction?

Cancer antigen 125 (CA-125) is a transmembrane glycoprotein, and it is known to be an essential biomarker in detecting treatment response and recurrence of ovarian cancer. It may also be used in monitoring colorectal cancer. It tends to rise in states of inflammation. Recent studies have demonstrated a temporary rise in CA-125 levels and other cancer biomarkers in patients suffering from coronavirus disease 2019 (COVID-19) infection. However, in the following case report, we hope to shed light on a possible association between CA-125 levels and the COVID-19 mRNA vaccine. We present the case of a 79-year-old woman with moderately differentiated adenocarcinoma of the right adnexa, who had a transient increase in CA-125 levels after a period, during which she underwent treatment for COVID-19 infection and received the first dose of COVID-19 mRNA (Pfizer-BioNTech) vaccine with no evidence of disease progression on imaging.