[Immediate hematological toxicity during combination chemotherapy-radiotherapy of Hodgkin's disease]

The hematologic immediate toxicity during radiotherapy for Hodgkin's disease was studied from a series of 72 patients with stage IIB or III who received 3 courses or more of chemotherapy before radiotherapy. The toxicity in the group of 36 of them who received total nodal irradiation (TNI) was the most important. Sixteen of the 28 TNI had irradiation interrupted, 12 of them began with inverted Y type. The blood cells count at the beginning of the treatment was crucial; only 16% of the patients had interruption of irradiation when the blood cells count was normal; on the other side, 63% had interruption when the blood cells count was abnormal (P less than 0.05). Toxicity was due to the daily destruction of the dividing bone marrow stem cells located in the irradiated area, from the first day of treatment; there was a progressive decrease in the pool of these stem cells within a late resaturation. The absence of resaturation of this pool after initial chemotherapy and after the first part of irradiation explained the immediate and durable toxicity; in the same way, inverted Y irradiation destroyed a great part of active bone marrow (40%) and the pool of remaining stem cells with high mitotic index would be located in areas irradiated subsequently. So, waiting for the absolute normalisation of blood cells count before beginning irradiation and start irradiation by mantle field (rather than inverted Y) seem to be the 2 measures able to reduce the number of interruptions of irradiation due to hematotoxicity.