Dosimetric and Radiobiological Evaluation of Multiparametric MRI-guided Dose Painting in radiotherapy of Prostate Cancer

Introduction: Radiotherapy is one of the treatment options for locally advanced prostate cancer, however with standard radiation doses it is not always very effective. One of the strategies to improve the efficiency of radiotherapy is increasing the dose. In this study to increase tumor local control rates a new radiotherapy method, known as dose painting (DP) was investigated.   Materials and Methods: Twenty-four consecutive patients with locally advanced prostate cancer who underwent an MP-MRI (T2w, DWI, DCE, MRS) scan, before a diagnostic biopsy from September 2015 to April 2016 were invited to take part in this study. Results: The TCP values for 3D-CRT, IMRT and DP techniques were 45%, 56% and 77%, respectively. The DP technique had a 37.5% and 71% higher TCP than IMRT and 3D-CRT, and these differences were statistically significant (P = 0.001). The mean NTCP values of the OARs for 3D-CRT, IMRT, and DP showed that there were statistically significant differences between them in three plans (p = 0.01). Conclusion: Dose painting by contours using MP-MRI is technically feasible. This study evaluated biological modeling based on both MP-MRI defined sub-volumes and pathologically defined sub-volumes. The MP-MRI guided dose painting results in the better TCP/ NTCP than 3D-CRT and IMRT.