Search

Purpose This study evaluated expected tumor control and normal tissue toxicity for prostate volumetric modulated arc therapy (VMAT) with and without radiation boosts to an intraprostatically dominant lesion (IDL), defined by 18 F-choline positron emission tomography/computed tomography (PET/CT). Methods and Materials Thirty patients with localized prostate cancer underwent 18 F-choline PET/CT before treatment. Two VMAT plans, plan 79 Gy and plan 100-105 Gy , were compared for each patient. The whole-prostate planning target volume (PTV prostate ) prescription was 79 Gy in both plans, but plan 100-105 Gy added simultaneous boost doses of 100 Gy and 105 Gy to the IDL, defined by 60% and 70% of maximum prostatic uptake on 18 F-choline PET (IDL suv60% and IDL suv70% , respectively, with IDL suv70% nested inside IDL suv60% to potentially enhance tumor specificity of the maximum point dose). Plan evaluations included histopathological correspondence, isodose distributions, dose-volume histograms, tumor control probability (TCP), and normal tissue complication probability (NTCP). Results Planning objectives and dose constraints proved feasible in 30 of 30 cases. Prostate sextant histopathology was available for 28 cases, confirming that IDL suv60% adequately covered all tumor-bearing prostate sextants in 27 cases and provided partial coverage in 1 case. Plan 100-105 Gy had significantly higher TCP than plan 79 Gy across all prostate regions for α/β ratios ranging from 1.5 Gy to 10 Gy ( P <.001 for each case). There were no significant differences in bladder and femoral head NTCP between plans and slightly lower rectal NTCP (endpoint: grade ≥ 2 late toxicity or rectal bleeding) was found for plan 100-105 Gy . Conclusions VMAT can potentially increase the likelihood of tumor control in primary prostate cancer while observing normal tissue tolerances through simultaneous delivery of a steep radiation boost to a 18 F-choline PET-defined IDL. [ABSTRACT FROM AUTHOR]