Granulocyte colony-stimulating factor treatment of leucopenia during fractionated radiotherapy

11 patients suffering from an isolated leucopenia during fractionated radiotherapy were treated with granulocyte colony stimulating factor (G-CSF). 4 of the patients received radiotherapy alone, and 7 patients received concomitant chemotherapy. G-CSF treatment was initiated at the occurrence of leucopenia and maintained for the duration of radiotherapy. The applied daily dose was 5 micrograms/kg subcutaneously. 10 of the 11 treated patients reacted with an increased leucocyte count, from an average of 1342 leucocytes per microliter (+/- 502/microliters) to 24,568 leucocytes per microliter (+/- 950/microliters). Neutrophil counts increased on average from 64.9% (+/- 13.9%) to 91.1% (+/- 2.3%) (n = 7). In 1 patient thrombocytopenia occurred during the continued radiotherapy. 1 other patient reacted with an unexplained fall of leucocytes after two doses of G-CSF and one fraction of mediastinal irradiation. Side-effects observed during G-CSF treatment consisted of mild bone pain (1/11) and transient increases of serum alkaline phosphatase levels (4/11). Our observations indicate that G-CSF treatment is well tolerated during continuous fractionated radiotherapy. Therefore, we conclude that G-CSF can be used clinically to alleviate neutropenia caused by radiotherapy or by combined radio-chemotherapy.