Use of tumour markers in monitoring the course of ovarian cancer

Background: There is a need to delineate how the best available serum marke r for ovarian cancer, CA 125 should be used in monitoring the treatment of individual patients, and in clinical trials. Patients and methods: The situations where measurement of CA 125 could alte r the management of individual patients during therapy and at relapse were critically analysed. Precise definitions for response according to CA 125 w ere first developed and tested on 989 patients receiving first line therapy and have since been tested on over 2000 patients in phase 2 trials. Precis e definitions for progression were developed from 71 patients during and on 255 patients both during and after initial chemotherapy. Results: In individual patient management, progression on initial chemother apy can be demonstrated by serial rise in CA 125 suggesting the need for a change in therapy. A confirmed doubling of CA 125 from the upper limit of n ormal during follow up accurately predicts relapse. This endpoint needs pro spective testing for use in clinical trials. Precise definitions of respons e based on a 50% or 75% fall in CA 125 levels accurately predicts whether a cytotoxic agent is active against ovarian cancer. Conclusion: Precise definitions of response based on CA 125 should be used in phase 2 trials of new cytotoxic drugs.