Comments on the Article “The Universal Dynamics of Tumor Growth” by A. Brú et al.

Abstract

We read with great interest the article published by Bru et al. titled “The Universal Dynamics of Tumor Growth” (Biophysical Journal 85:2948–2961). Therein, a number of in vitro growing cell line colonies and developing in vivo developing tumors are analyzed. Bru et al. infer that their results indicate a common growth dynamics that is compatible with the molecular beam epitaxy (MBE) process. The authors achieved this conclusion based on the following reasoning. First, a fractal analysis of the contours was performed. Once the universality class was identified by means of that analysis, a stochastic equation sharing the same universality class was introduced: the linear MBE model. Then, experimental assays to test the features imposed by that model were carried out. Herein, we demonstrate that the scaling analysis performed by the authors is inconsistent and consequently misleading. Moreover, we also show that the experimental evidence provided to check the characteristics imposed by the linear MBE equation do not point exclusively to that model. Finally, we indicate the source of such inconsistent analysis, namely, an effect due to the geometry of tumors, and how to fix it.