HEMATOLOGIC TOXICITY DURING CRANIOSPINAL IRRADIATION - THE IMPACT OF PRIOR CHEMOTHERAPY

The purpose of this work was to determine the frequency of hematologic toxicity during craniospinal radiation (CSI) and the impact of preirr adiation chemotherapy on this frequency. The charts of 37 patients who received CSI were reviewed. Twenty did not have prior chemotherapy (C T-), while 17 did receive 1 to 18 (means 5) cycles of multi-agent syst emic chemotherapy (CT +). Leukopenia/thrombocytopenia necessitating tr eatment interruptions occurred in 1/20 (5%) in the CT - group, compare d to 8/17 (47%) among the CT + group. This difference was statisticall y significant, P < 0.0001 (Fisher's exact two-tailed test). The durati on of treatment interruption in the CT + patients was 4-24 days (mean 14). Compared to the CT - group, the CT + group had a statistically si gnificant greater decline in their white blood cell count (WBC), plate let count, and hematocrit (HCT) during CSI (percent reduction per Gy; (P = 0.018, 0.006, and 0.047, respectively). Although not statisticall y significant, the CT + group also experienced lower nadir ratios (nad ir count/baseline count) in terms of WBC and platelets (P = 0.07 and 0 .22, respectively). While the mean pretreatment baseline blood counts were lower in the CT + group compared to the CT - group, these differe nces reached statistical significance for the HCT (P = 0.02), but not the WBC (P = 0.59) or platelets (P = 0.43). Leukopenia and thrombocyto penia are very common in patients who receive craniospinal irradiation following multi-agent systemic chemotherapy. This appears to be due t o more rapid and marked reductions in counts during CSI. Since this to xicity may cause treatment interruptions that are potentially therapeu tically disadvantageous, aggressive hematologic support with transfusi ons and growth factors may be necessary. This problem may become more common as combined modality therapy is used more frequently.