The effect of drug schedule on mouse neuroblastoma treated with cyclophosphamide.

The potential difference in survival due to scheduling of cyclophosphamide treatment was examined in A/J mice inoculated with neuroblastoma C1-1300 cells. Treatment was started on the third day post tumor implantation. There were four groups of animals each consisting of 30 mice: Group A, a control group, was injected with 0.3 cc of normal saline for a week. Group B was injected with cyclophosphamide 50 mg/kg/day every other day for five doses. This cycle was repeated in the same fashion starting on day 17. Group C was injected with cyclophosphamide 250 mg/kg on day 3 and this was repeated on day 17. Group D was injected with cyclophosphamide 50 mg/kg/day for five consecutive days. This cycle was repeated on day 17-21. The median survival for group B was 26.2 days (the same as the control group), for group C 47.7 days (87% increased survival) and for group D 63.2 days (143% increased survival with 30% possible cures). Twenty-three percent of the mice in group B died of pneumonia and another 23% had minor evidence of lung infection. Only three mice in this group had tumor at the time of death. The study suggests that the response of murine neuroblastoma as well as the development of pneumonia in A/J mice treated with cyclophosphamide might be schedule dependent.