Concordance between disease progression by Cancer Antigen 125 and computerized tomography (CT) progression in patients with relapsed advanced ovarian cancer treated with poly(adenosine diphosphate [ADP]–ribose) polymerase inhibitor: a pooled analysis

Women with relapsed advanced ovarian cancer are typically treated with chemotherapy. After completing chemotherapy, these women are usually followed up with blood tests, including the tumour marker Cancer Antigen 125 (CA-125). Computerized tomography (CT) scans are usually triggered when the CA-125 rises or doubles, or if women experience symptoms suggesting that the cancer has returned.

In recent years, PARP inhibitor therapy following chemotherapy has improved outcomes for certain groups of women with advanced ovarian cancer and is now widely used. PARP inhibitor therapy block PARP enzymes in cancer cells. PARP enzymes help repair DNA damage. Blocking PARP enzymes prevent cancer cells from repairing DNA damage and as a result, these cancer cells die. However, there is limited knowledge on the best way to monitor women on PARP inhibitor therapy. The studies of PARP inhibitor therapy used regular CT scans to detect cancer progression but in clinical practice, these women are usually followed up with blood tests, including CA-125, and CT scans are only performed when the CA-125 rises or there are symptoms of concern.

We analysed whether CA-125 is a reliable marker for cancer progression as detected by CT by using the data from the SOLO2/ENGOT-Ov21 clinical trial. We found that doubling of CA-125 reliably predicts for cancer progression as detected by CT. However, we found a considerable proportion of patients with a normal CA-125 still experience cancer progression as seen on a CT scan. Our findings raise the question of whether we need to consider regular CT scans in women treated by PARP inhibitor therapy. Detecting cancer progression is important to avoid unnecessary side effects and consider alternative treatment options for these women.

It is important to confirm our findings by pooling data from other studies of women with advanced ovarian cancer treated with PARP inhibitor therapy. Pooling data from other studies allows us to assess the reliability of CA-125 in determining cancer progression with more certainty and in a broader group of women. Our work has the potential to change existing guidelines and improve on the way we monitor women treated with PARP inhibitor therapy.