55. How often should we obtain complete blood counts (CBC's) from patients receiving radical radiation therapy?

Data on factors influencing decline in peripheral blood counts during radiation treatment are sparse and no guidelines exist on the appropriate frequency of obtaining CBC's from the patients.Patients and methodsA series of charts from 460 consecutive patients receiving radiotherapy in 1995 and 1996 was reviewed. In the final database, the data from patients receiving definitive radiotherapy with information on baseline CBC's and at least two results during treatment were included (183 patients, 810 results). Critical nadir values of haemoglobin (HGB), white blood cells (WBC) and platelets (PLT) requiring further tests and interventions were defined as follows: HGB<9.0 g/dL, WBC<2.000/mm3, PLT<100/mm3. For statistical analysis, logistic regression was used separately for each parameter and then the prognostic model of obtaining at least one nadir value in all tests performed in one patient was developed.ResultsOf 183 patients, at least one nadir value was observed in 17 patients (9%). Pre-treatment CBC was very strong and the only predictor of nadirs – the other variables were not significant in the final model. The probability of at least one nadir during treatment was 35% if one of the following pre-treatment CBC values was noted: HGB<11.0 g/dL, WBC<5.000/mm3 or PLT