Growth Laws in Cancer Implications for Radiotherapy.pdf

a r X i v : p h y s i c s / 0 6 0 8 2 7 8 v 1 [ p h y s i c s .m e d - p h ] 2 9 A u g 2 0 0 6 Growth Laws in Cancer: Implications for Radiotherapy P.Castorina(a,b), T.S.Deisboeck(c),P. Gabriele(d) C.Guiot(e,f)1 1(a) Dipartimento di Fisica, Universita’ di Catania, Italy (b) INFN-Catania, Italy (c) Complex Biosystems Modeling Laboratory, Harvard-MIT (HST) Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA 02129. (d) Institute for Cancer Research and Cure, IRCC, Candiolo (TO), Italy (e) INFM- Torino UNiversita’ e Politecnico, Italy (f) Dipartimento Neuroscienze, Universita’ di Torino, Italy ABSTRACT Comparing both, the more conventional Gompertz tumor growth law (GL) and the “Universal” law (UL), recently proposed and applied to cancer, we have investigated the growth law’s implications on various radiotherapy regimen. According to GL, the surviving tumor cell fraction could be reduced ’ad libidum’, independently of the initial tumor mass, simply by increasing the number of treatments. On the contrary, if tumor growth dynamics would indeed follow the Universal scaling law, there is a lower limit of the survival fraction that cannot be reduced any further regardless of the total number of treatments. This finding can explain the so called “tumor size effect” and re-emphasizes the importance of early diagnosis as it implies that radiotherapy may be successful provided the tumor mass at treatment onset is rather small. Taken together with our previous works, implications of these findings include revisiting standard radiotherapy regimen and overall treatment protocols. 2INTRODUCTION A more detailed understanding of tumor growth is crucial for the clinical management of the disease and tumor size is a main determinant of clinical severity and a major factor of the staging criteria before and during radiotherapy (RT) [1] Tumor regrowth during radiotherapy is therefore an important clinical parameter [2]and, in parti