Carboplatin dose in combination chemotherapy for testicular cancer.

Carboplatin was given in escalating doses in combination with etoposide and bleomycin (CEB) to 36 patients with testicular cancer. The platelet nadirs but not the white cell nadir correlated significantly with the dose of carboplatin administered. The best correlation was seen with area under the curve (AUC) calculated from a knowledge of the glomerular filtration rate (GFR). A further 40 patients were treated with a carboplatin dose calculated to give an AUC of 4.6 or 5.0 mg.min/ml. From the first part of the study it was predicted that 5-10% of the patients would have significant thrombocytopenia with the first course of treatment. The observed incidence was in fact 5%. When dose escalation and reduction were carried out for platelet nadirs falling outside the range 50-100 x 10(9)/l the average cumulative dose after four courses of carboplatin was very similar to four times the starting dose. Furthermore, as many reductions as escalations were carried out. Thus a starting dose for carboplatin calculated to give an AUC of 5.0 mg.min/ml in the CEB combination is one which will produce an acceptable level of thrombocytopenia. The CEB combination was found to produce a cumulative suppression of platelet nadirs. A mean net fall in haemoglobin of 7.5-9.5% was seen with each cycle.