Baseline blood work before initiation of chemotherapy: what is safe in the real world?

Introduction: This is an observational study of patterns of practice of the timing of baseline blood work (BBW) before chemotherapy initiation. The primary objective was to evaluate the incidence of significant changes in laboratory values within 6 weeks before therapy.

Methods: All consecutive patients receiving chemotherapy within a 6-month period were analyzed retrospectively. Time interval between date of chemotherapy initiation and nearest blood work was calculated. Data from patients with one or more sets of values within 6 weeks were used to evaluate dosing changes. Changes in laboratory values collected closest to the date of chemotherapy and values collected before that but within 6 weeks were graded according to the National Cancer Institute's Common Toxicity Criteria. A change of ≥1 grade was considered clinically meaningful.

Results: Five hundred ninety-two patients were included. Median interval between BBW and initiation of chemotherapy was 4 days. Three hundred thirty-five patients had two or more sets of laboratory tests within the 6-week period, 33% of patients had a meaningful change in one or more values. The majority of changes occurred in hemoglobin (22%), ALT (14%), WBC (11%) and AST(10%), yet only 66% of patients had liver function tests as part of the BBW.

Conclusions: Adherence to the institutional recommendation of BBW within 6 weeks was high. Baseline laboratory tests performed within 7 days of chemotherapy initiation would have detected nearly all significant changes; therefore, we suggest that this interval be tested in future randomized trials.