PurposeTo assess the performance of a proton-specific knowledge-based planning (KBP) model in the creation of robustly optimized intensity-modulated proton therapy (IMPT) plans for treatment of advanced head and neck (HN) cancer patients.MethodsSeventy-three patients diagnosed with advanced HN cancer previously treated with volumetric modulated arc therapy (VMAT) were selected and replanned with robustly optimized IMPT. A proton-specific KBP model, RapidPlanPT (RPP), was generated using 53 patients (20 unilateral cases and 33 bilateral cases). The remaining 20 patients (10 unilateral and 10 bilateral cases) were used for model validation. The model was validated by comparing the target coverage and organ at risk (OAR) sparing in the RPP-generated IMPT plans with those in the expert plans. To account for the robustness of the plan, all uncertainty scenarios were included in the analysis.ResultsAll the RPP plans generated were clinically acceptable. For unilateral cases, RPP plans had higher CTV_primary V100 (1.59% ± 1.24%) but higher homogeneity index (HI) (0.7 ± 0.73) than had the expert plans. In addition, the RPP plans had better ipsilateral cochlea Dmean (−5.76 ± 6.11 Gy), with marginal to no significant difference between RPP plans and expert plans for all other OAR dosimetric indices. For the bilateral cases, the V100 for all clinical target volumes (CTVs) was higher for the RPP plans than for the expert plans, especially the CTV_primary V100 (5.08% ± 3.02%), with no significant difference in the HI. With respect to OAR sparing, RPP plans had a lower spinal cord Dmax (−5.74 ± 5.72 Gy), lower cochlea Dmean (left, −6.05 ± 4.33 Gy; right, −4.84 ± 4.66 Gy), lower left and right parotid V20Gy (left, −6.45% ± 5.32%; right, −6.92% ± 3.45%), and a lower integral dose (−0.19 ± 0.19 Gy). However, RPP plans increased the Dmax in the body outside of CTV (body-CTV) (1.2 ± 1.43 Gy), indicating a slightly higher hotspot produced by the RPP plans.ConclusionIMPT plans generated by a broad-scope RPP model have a quality that is, at minimum, comparable with, and at times superior to, that of the expert plans. The RPP plans demonstrated a greater robustness for CTV coverage and better sparing for several OARs.

Purpose To assess the performance of a proton-specific knowledge based planning (KBPP) model in creation of robustly optimized intensity-modulated proton therapy (IMPT) plans for treatment of patients with prostate cancer. Materials and Methods Forty-five patients with localized prostate cancer, who had previously been treated with volumetric modulated arc therapy, were selected and replanned with robustly optimized IMPT. A KBPP model was generated from the results of 30 of the patients, and the remaining 15 patient results were used for validation. The KBPP model quality and accuracy were evaluated with the model-provided organ-at-risk regression plots and metrics. The KBPP quality was also assessed through comparison of expert and KBPP-generated IMPT plans for target coverage and organ-at-risk sparing. Results The resulting R2 (mean ± SD, 0.87 ± 0.07) between dosimetric and geometric features, as well as the χ2 test (1.17 ± 0.07) between the original and estimated data, showed the model had good quality. All the KBPP plans were clinically acceptable. Compared with the expert plans, the KBPP plans had marginally higher dose-volume indices for the rectum V65Gy (0.8% ± 2.94%), but delivered a lower dose to the bladder (−1.06% ± 2.9% for bladder V65Gy). In addition, KBPP plans achieved lower hotspot (−0.67Gy ± 2.17Gy) and lower integral dose (−0.09Gy ± 0.3Gy) than the expert plans did. Moreover, the KBPP generated better plans that demonstrated slightly greater clinical target volume V95 (0.1% ± 0.68%) and lower homogeneity index (−1.13 ± 2.34). Conclusions The results demonstrated that robustly optimized IMPT plans created by the KBPP model are of high quality and are comparable to expert plans. Furthermore, the KBPP model can generate more-robust and more-homogenous plans compared with those of expert plans. More studies need to be done for the validation of the proton KBPP model at more-complicated treatment sites.

Background To assess the feasibility of CBCT-based adaptive intensity modulated proton therapy (IMPT) using automated planning for treatment of head and neck (HN) cancers. Methods Twenty HN cancer patients treated with IMPT and had daily CBCTs were included. Initial IMPT plans were created using automated planning software for all patients. Synthetic CTs (sCT) were created by deforming planning CT (pCT) to CBCTs. rCTs were deformed to CBCT obtained on the same day to create deformed rCT (rCTdef) as gold standard. Doses recalculated on sCT and rCTdef with the were compared using gamma analysis. The dosimetric parameters were assessed based on rCTdef, sCT with deformably propagated contours or with physician-corrected contours. Weekly sCTs were then created for all patients. For non-adaptive group, dose was directly recalculated on weekly sCTs. For adaptive group, adaptive IMPT plans were created on weekly sCT using the automated planning software. The non-adapted and adapted dose-volume parameters on weekly sCTs were evaluated. The weekly doses were accumulated back to the pCT for both groups, and dosimetric parameters were compared in between. Results High dosimetric agreement was found between sCT and rCTdef with high gamma passing rate of 97.4%±1.6% using 3mm/3% criteria. With contour correction on sCT by physician, the uncertainty range of using sCT to estimate mean dose for organ at risk (OARs) can be reduced to (-2.37%, 2.19%), while for V95 of primary or secondary CTVs, the uncertainty can be controlled within (-1.09%, 0.29%). For non-adapted treatments, 15.7%, 34% and 55.7% of the fractions didn’t meet the V95 > 98% constraint for primary, secondary and tertiary CTVs respectively while all adaptive fractions met the constraint. In the accumulated dose, adaptive planning significantly reduced mean dose to constrictors (-1.42Gy ± 2.79Gy) and larynx (-2.58Gy ± 3.09Gy) compared to non-adaptive group, resulting in significantly reduction on the normal tissue complication probability (NTCP) of larynx edema by 7.52%± 13.59%. Conclusion sCT can be a powerful tool for accurate proton dose calculation. Physician contour correction is recommended to reduce the uncertainty for dose evaluation. Daily adaptation resulted in better CTV coverage, OAR sparing and lower NTCP for some OARs as compared with non-adaptive IMPT.