Purpose
RECIST evaluation does not take into account the pre-treatment tumor kinetics and may provide incomplete information regarding experimental drug activity. Tumor Growth Rate (TGR) allows for a dynamic and quantitative assessment of the tumor kinetics. How TGR varies along the introduction of experimental therapeutics and is associated with outcome in phase I patients remains unknown.
Experimental designs
Medical records from all patients (n=253) prospectively treated in 20 phase I trials were analyzed. TGR was computed during the pre-treatment period (REFERENCE) and the EXPERIMENTAL period. Associations between TGR, standard prognostic scores (RMH score) and outcome (PFS, OS) were computed (multivariate analysis).
Results
We observed a reduction of TGR between the REFERENCE vs. EXPERIMENTAL periods (38% vs. 4.4%, P<.00001). Although most patients were classified as stable disease (65%) or progressive disease (25%) by RECIST at the first evaluation, 82% and 65% of them exhibited a decrease in TGR, respectively. In a multivariate analyses, only the decrease of TGR was associated with PFS (P=.004), whereas the RMH score was the only variable associated with OS (P=.0008). Only the investigated regimens delivered were associated with a decrease of TGR (P<.00001, multivariate analysis). Computing TGR profiles across different clinical trials reveals specific patterns of antitumor activity.
Conclusions
Exploring TGR in phase I patients is simple and provides clinically relevant information: (i) an early and subtle assessment of signs of antitumor activity; (ii) indpendent association with PFS; and (iii) It reveals drug-specific profiles; suggesting potential utility for guiding the further development of the investigational drugs.
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