  We have previously reported that a universal growth law, as proposed by West
and collaborators for all living organisms, appears to be able to describe also
the growth of tumors in vivo. In contrast to the assumption of a fixed power
exponent p (assumed by West et al. to be equal to 3/4), we show in this paper
the dynamic evolution of p from 2/3 to 1, using experimental data from the
cancer literature and in analogy with results obtained by applying scaling laws
to the study of fragmentation of solids. The dynamic behaviour of p is related
to the evolution of the fractal topology of neoplastic vascular systems and
might be applied for diagnostic purposes to mark the emergence of a
functionally sufficient (or effective) neo-angiogenetic structure.
