Growth delay does not only reflect the effect of treatment on the tumor parenchymal cells but also on the stroma. Due to tumor bed effect, the extent of growth delay determined from tumor growth curves is highly dependent on the end volume chosen. It was aimed to minimize the influence of the tumor bed effect on the growth delay calculated by choosing a smaller size and essentially an earlier time for regrowth. Net growth delay is a novel parameter derived from the tumor growth curves, allowing a better comparison of the results with colony assay and tumor control data.
