Monte carlo simulation of electron dose from 131I-targeted tumor cells within a heterogeneous tumor

Paolo Zanotti-Fregonara, Christophe Champion, Maria Cristina Marzola, Domenico Rubello, Pierre Alexandre Just, Jean Luc Moretti, Elif Hindié

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Background and Aim: In internal radiotherapy, the variable distribution of target receptors within the tumoral tissue, and the variable ranges of electrons may be responsible for a heterogeneous dose distribution at the cellular level. The aim of the present study was to use Monte Carlo simulations to assess 131I electron dose in a model of heterogeneous tumor containing multiple clusters of cancer cells, targeted by 131I-labeled molecules. Methods: The model consisted of 150-μm-diameter spherical tumor cell clusters, in which 131I was homogeneously distributed. Clusters were placed 24 μm apart, separated by septa of nonradioactive connective tissue. The electron dose distribution to tumor cells in a single cluster was first assessed. Then was assessed the dose increase to these targets after adding multiple layers of neighboring clusters (total number of clusters = 15,624). Results: Dose distribution within a single isolated cluster follows a decreasing gradient, the dose for the outermost cell layer being about half that at the center. When radioactive neighbors were added, the dose to the central cluster increased. The most important contribution was given by the nearest neighbors, whereas the contribution from neighbors beyond a distance of 1 mm was only for 5% of the final dose. If the central cluster was unlabeled, the absorbed dose to the outermost cell layer of this cluster was reduced by 27%, and that at the center by 45%. Conclusions: The electron cross-dose of 131I falls rapidly as a function of distance and becomes negligible after just 1 mm. Small clusters of tumor cells that are not radiolabeled may receive a very small dose. Therefore, in internal radiotherapy it is important to aim at targeting tumor cells as homogeneously as possible, rather than relying on the cross-dose to achieve a therapeutic effect.

Original languageEnglish (US)
Pages (from-to)135-140
Number of pages6
JournalCancer Biotherapy and Radiopharmaceuticals
Issue number1
StatePublished - Feb 1 2011


  • Monte Carlo
  • cellular dosimetry
  • internal radiotherapy

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Pharmacology
  • Cancer Research


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