A generalized "tumor growth delay" assay for quantifying alterations of tumor regrowth patterns

Tumor growth delay (TGD) is a widely accepted method for in situ assessment of tumor treatment modalities. However, it has some drawbacks: (1) dependency on arbitrary endpoints and, even more serious, (2) lack of alterations of the tumor-growth pattern after treatment. In the present study a generalization of TGD is proposed which is based on the analysis of tumor growth curves by applying the difference equation of the Gompertz function. The advantages of the present method consist primarily of addressing the drawbacks of the classical assay mentioned above: generalized TGD permits a quantitative evaluation of treatment-induced alterations of tumor-growth patterns after treatment as well as estimations of TGD in a classical form by comparing growth curves as entities, i.e. independently of endpoints. The possibility of studying dose-effect relationships of antineoplastic treatment modalities by the generalized TGD is demonstrated by applying this method on experimental chemotherapy and radiotherapy data.