GESTATIONAL TROPHOBLASTIC TUMORS - CYTOSTATIC TREATMENT RESPONSE EVALUATED FROM HCG MODELING

Fifty-eight patients representing with gestational trophoblastic tumor s were treated at the department of Gynaecologic Oncology of the Norwe gian Radium Hospital during the period from 1977 to 1990. Individual s erial measurements of hCG were analyzed applying a mathematical dynami c tumor marker model. Fifty-three low-median risk patients were given standard cytotoxic chemotherapy with a methotrexate-actinomycin regime n. The surving fraction of hCG-producing cells following the first che motherapy cycle decreased exponentially with methotrexate dose. The es timated surviving fraction of hCG-producing cells was not a prognostic factor in those patients who needed second-line chemotherapy. These p atients, however, were characterized by high pre-treatment hCG levels and rapid proliferation of hCG-producing cells. Five patients, three h igh risk and two medium risk, were allocated to a high dose methotrexa te regimen. Surviving fractions of hCG-producing cells in high dose me thotrexate were a factor of 3-10 times lower than the surviving cell f ractions in the low dose regimen, indicating a biphasic dose-response relation for methotrexate. Medium risk patients were found to have an unacceptably high recurrence rate after methotrexate actinomycin-D the rapy and should be treated with more intensive chemotherapy. It is rec ommended that drug dose should be corrected for body-volume in low ris k regimes, to avoid drug resistance developing because of increased tr eatment time.