Influence of tumor shape and location in eye plaque brachytherapy dosimetry.
PURPOSE: A common treatment planning technique for eye plaque brachytherapy is to model the tumor as an ellipse. For posterior tumors near the optic disc and fovea, this approach may lead to overlap between tumor and the organ at risk (OAR). We hypothesized that a superior plan can be generated by modeling the actual tumor shape.
MATERIALS AND METHODS: Forty eye plaque patients with tumorsplan, and Wilcoxon signed-rank tests were used to asses any statistically significant differences.
RESULTS: Equivalent tumor coverage was confirmed between the elliptical and true tumor plans for all patients. Qualitative analysis showed greater dosimetric differences between plans as the distance from the OARs increased from 0 to 2 mm but the largest differences were observed between 2 and 4 mm. Minimal differences between models were seen beyond 4 mm. Statistically significant dosimetric improvements were found for tumorsdisc.
CONCLUSIONS: Intuitively, accurate modeling of the tumor accounting for irregularities in the shape should result in a more conformal plan and an overall reduction in OAR dose. However, this technique is only beneficial for tumors that are within 4 mm of the fovea or optic disc. An elliptical tumor model allows for an acceptable plan unless the tumor is located posteriorly and has an irregular shape.
Published In/Presented At
Studenski, M. T., Patel, N. V., Markoe, A., Harbour, J. W., & Samuels, S. E. (2020). Influence of tumor shape and location in eye plaque brachytherapy dosimetry. Brachytherapy, 19(2), 249–254. https://doi.org/10.1016/j.brachy.2020.01.001
Medicine and Health Sciences | Oncology
Department of Radiation Oncology