Impact of acute hematological toxicity on treatment interruptions during cranio-spinal irradiation in medulloblastoma: a tertiary care institute experience.

To analyze treatment interruptions due to acute hematological toxicity in patients of medulloblastoma receiving cranio-spinal irradiation (CSI). Prospectively collected data from case records of 52 patients of medulloblastoma treated between 2011 and 2014 was evaluated. Blood counts were monitored twice a week during CSI. Spinal irradiation was interrupted for patients with ≥grade 2 hematological toxicity and resumed after recovery to grade 1 level (TLC >3000; platelet count >75,000). Treatment interruptions and hematological toxicity were analyzed. Median age was 11 years. All patients received adjuvant CSI of 36 Gy, followed by boost of 18 Gy to posterior fossa, at 1.8 Gy per fraction. Concurrent chemotherapy was not given. Adjuvant chemotherapy was given after CSI for high risk patients. Spinal fields were interrupted in 73.1% of patients. Cause of first interruption was leucopenia in 92.1%, thrombocytopenia in 2.6%, and both in 5.3%. Median number of fractions at first interruption was 8, with 25% of interruptions in first week. Median duration for hematological recovery after nadir was 5 days for leucopenia and 3 days for thrombocytopenia. Half of the patients had at least 2 interruptions, and 19% subsequently developed grade 3 toxicity. On multivariate analysis, significant correlation with duration of delay was observed for pre-treatment haemoglobin, number of fractions at first interruption, grade and duration of recovery of leucopenia. Acute hematological toxicity with CSI is frequently under-reported. Patients with low pre-treatment hemoglobin, early onset leucopenia, profound leucopenia and prolonged recovery times are at a higher risk of having protracted courses of irradiation. Frequent monitoring of blood counts and timely interruption of spinal fields of irradiation at grade 2 level of hematological toxicity minimizes the risk of grade 3 and grade 4 toxicity, while reducing the interruptions in irradiation of the gross tumour bed.