Abstract
Few studies have directly compared passive scattering (PS) to intensity-modulated proton therapy (IMPT) in the delivery of ultra-hypofractionated proton beams to the localized prostate cancer (PCa). In this preliminary study involving five patients previously treated with CyberKnife, treatment plans were created for PS and IMPT (36.25 CGE in five fractions with two opposing fields) to compare the dosimetric parameters to the planning target volume (PTV) and organs-at-risk (OAR: rectum, bladder, femoral heads). Both plans met the acceptance criteria. Significant differences were observed in the minimum and maximum doses to the PTV. The mean dose to the PTV was lower for PS (35.62 ± 0.26 vs. 37.18 ± 0.14; p = 0.002). Target coverage (D98%) was better for IMPT (96.79% vs. 99.10%; p = 0.004). IMPT resulted in significantly lower mean doses to the rectum (16.75 CGE vs. 6.88 CGE; p = 0.004) and bladder (17.69 CGE vs. 5.98 CGE p = 0.002). High dose to the rectum (V36.25 CGE) were lower with PS, but not significantly opposite to high dose to the bladder. No significant differences were observed in mean conformity index values, with a non-significant trend towards higher mean homogeneity index values for PS. Non-significant differences in the gamma index for both fields were observed. These findings suggest that both PS and IMPT ultra-hypofractionated proton therapy for PCa are highly precise, offering good target coverage and sparing of normal tissues and OARs.
Highlights
Hypofractionated radiotherapy has many advantages over conventional fractionation schemes, including shorter treatment times and more effective cell killing due to the greater sensitivity of prostate cancer cells to high doses per fraction [1,2,3,4,5,6,7,8], which explains the growing interest in this approach to treat a wide range of tumour types, including prostate cancer (PCa) [9]
conformity index (CI) values, but there was a trend towards higher mean homogeneity index (HI) values for passive scattering (PS). These findings suggest that both PS and intensity-modulated proton therapy (IMPT) ultra-hypofractionated proton therapy for localized PCa are highly precise, offering good target coverage and sparing of normal tissues and organs at risk (OARs)
We found that mean planning target volume (PTV) doses for both techniques (PS and IMPT, 35.62 and 37.18 cobalt gray equivalent (CGE), respectively) were lower than those reported by Kole et al (37.6 CGE) [10]
Summary
Hypofractionated radiotherapy has many advantages over conventional fractionation schemes, including shorter treatment times and more effective cell killing due to the greater sensitivity of prostate cancer cells to high doses per fraction [1,2,3,4,5,6,7,8], which explains the growing interest in this approach to treat a wide range of tumour types, including prostate cancer (PCa) [9].Stereotactic body radiotherapy (SBRT) is a technique involving the precise delivery of highly conformal, hypofractionated radiation delivered in the form of a photon beam.Highlighted technique is implemented to radiotherapy using a proton beam. There has been a growing interest in ultra-hypofractionated radiotherapy This technique involves the administration of large daily fractions (4 to 8 Gy), which can be delivered through either photon or proton beam therapy [10,11,12,13,14,15]. Both techniques can achieve satisfactory results, proton therapy has a theoretical advantage in terms of better sparing of normal tissues due to dose modulation along the beam path to create a spread-out Bragg peak (SoBP). Several studies have compared these techniques, without finding any significant differences in terms of late gastrointestinal (GI) or genitourinary (GU) toxicity [16,17,18,19]
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