  In radiation therapy tumor size, and thus also volume, has a significant
impact on the local control of tumors. Moreover, tumor volume is a significant
prognostic factor for modelling and predicting therapeutic outcomes in cancer
treatment. In research, the distribution of tumor volumes in patient
populations has so far remained widely unexplored. In this work, the frequency
distributions of maximum diameter of tumors for various types of cancer was
studied based on SEER data and it was explored if they can be modelled using
Weibull distributions. Further, actual volume data were obtained directly from
computer tomography (CT) datasets and the frequency distributions of tumor
volumes and maximum diameters were explored and a link between them was found.
In cancer research, tumors are often modelled as ellipsoids. In order to verify
the appropriateness of using ellipsoids as a model, to the obtained
three-dimensional data, ellipsoids were fitted and the resulting volumes and
diameters analysed. Finally, NSCLC tumor diameters were Monte Carlo simulated
using tumor growth and incidence models. A comparison of the simulated tumor
diameter distributions with observed SEER data yielded the determination of
tumor growth rates.
