Treatment plan comparison of linac step and shoot, tomotherapy, rapidarc, and proton therapy for prostate cancer by using the dosimetrical and the biological indices

Abstract

The purpose of this study was to use various dosimetrical indices to determine the best IMRT modality technique for treating patients with prostate cancer. Ten patients with prostate cancer were included in this study. Intensity modulated radiation therapy plans were designed to include different modalities, including the linac step and shoot, Tomotherapy, RapidArc, and Proton systems. Various dosimetrical indices, like the prescription isodose to target volume (PITV) ratio, conformity index (CI), homogeneity index (HI), target coverage index (TCI), modified dose homogeneity index (MHI), conformation number (CN), critical organ scoring index (COSI), and quality factor (QF) were determined to compare the different treatment plans. Biological indices such as the generalized equivalent uniform dose (gEUD), based tumor control probability (TCP), and normal tissue complication probability (NTCP) were also calculated and used to compare the treatment plans. The RapidArc plan attained better PTV coverage, as evidenced by its superior PITV, CI, TCI, MHI, and CN values. Regarding OARs, proton therapy exhibited superior dose sparing for the rectum and bowel in low dose volumes, whereas the Tomotherapy and RapidArc plans achieved better dose sparing in high dose volumes. The QF scores showed no significant difference among these plans (p=0.701). The average TCPs for prostate tumors in the RapidArc, Linac, and Proton plans were higher than the average TCP for Tomotherapy (98.79%, 98.76%, and 98.75% vs. 98.70%, respectively). Regarding the rectum NTCP, RapidArc showed the most favorable result (0.09%), whereas Linac resulted in the best bladder NTCP (0.08%).[22]. Similarly, Cotter et al. compared proton radiotherapy versus IMRT for pediatric prostate rhabdomyosarcoma. This study provides evidence of significant dose savings to normal structures with proton radiotherapy compared to IMRT [19]. As described above, several studies have compared the results of various IMRT delivery techniques. However, studies comparing prostate cancer outcomes for treatment plans using the Linac step and shoot technique, Tomotherapy, RapidArc, or proton modalities are limited.The purpose of this study was thus to determine the best modality out of four possible modalities for treating patients with prostate cancer. To this end, we compared the dosimetric physical indices, EUDbased TCP scores, and EUD-based NTCP scores for different IMRT plans used to treat ten different patients with prostate cancer.

Volumetric-Modulated Arc Radiotherapy with Daily Image-Guidance Carries Better Toxicity Profile for Higher Risk Prostate Cancer

“…A dosimetric Korean study compared both modalities used in our study as well as Tomotherapy and Proton. Authors concluded that better PTV coverage and superior rectal and bowel sparing in high dose volumes were attained with VMAT compared to other modalities albeit all of them achieved the desired constraints (Lee et al, 2015). Nevertheless, no dosimetric advantage was reported in this work.…”

Dosimetric Evaluation of Advanced Radiotherapy Techniques in Treating Patients with Prostatic Cancer

“…Lee et al performed a planning study on ten patients with prostate cancer 29 . Different modalities of IMRT were used, like the linac step and shoot, RapidArc and proton systems.…”