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Neurovascular Bundle Infiltration Can Explain Local Relapses Using Conformal Radiotherapy of Prostate Cancer
Andreas K Johansson1,2, Bo Lennernäs3, Ulf Isacsson4
1Section of Medical Physics, Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, Sweden andreas.johansson@igp.uu.se.
Aim:
To quantify the impact of decreased margins for two treatment techniques, three-dimensional conformal radiotherapy (3D-CRT) and volumetric-modulated arc therapy (VMAT), on local control in curative treatment of prostate cancer.
Materials And Methods:
The planning target volume (PTV) margins were decreased in steps of 1 mm from 10 to 1 mm. Treatment plans using 3D-CRT and VMAT technique were produced for all margin sizes and the dose to the neuro vascular bundles (NVB), that was not included in the PTV, was investigated.
Results:
Due to the more conformal dose delivery using VMAT, the dose to the NVB decreased more rapidly by VMAT compared to the 3D-CRT plans. The dose difference was significant for margins from 1-7 mm.
Conclusion:
One should be very cautious before clinical routines are changed, bearing in mind whether the change means more conformal treatment technique, smaller margins or target segmentation in different imaging modalities.