Abstract
To investigate the plan quality of tri-Co-60 intensity-modulated radiation therapy (IMRT) with magnetic-resonance image-guided radiation therapy compared with volumetric-modulated arc therapy (VMAT) for prostate cancer. Twenty patients with intermediate-risk prostate cancer, who received radical VMAT were selected. Additional tri-Co-60 IMRT plans were generated for each patient. Both primary and boost plans were generated with tri-Co-60 IMRT and VMAT techniques. The prescription doses of the primary and boost plans were 50.4 Gy and 30.6 Gy, respectively. The primary and boost planning target volumes (PTVs) of the tri-Co-60 IMRT were generated with 3 mm margins from the primary clinical target volume (CTV, prostate + seminal vesicle) and a boost CTV (prostate), respectively. VMAT had a primary planning target volume (primary CTV + 1 cm or 2 cm margins) and a boost PTV (boost CTV + 0.7 cm margins), respectively. For both tri-Co-60 IMRT and VMAT, all the primary and boost plans were generated that 95% of the target volumes would be covered by the 100% of the prescription doses. Sum plans were generated by summation of primary and boost plans. In sum plans, the average values of V70 Gy of the bladder of tri-Co-60 IMRT vs. VMAT were 4.0% ± 3.1% vs. 10.9% ± 6.7%, (p < 0.001). Average values of V70 Gy of the rectum of tri-Co-60 IMRT vs. VMAT were 5.2% ± 1.8% vs. 19.1% ± 4.0% (p < 0.001). The doses of tri-Co-60 IMRT delivered to the bladder and rectum were smaller than those of VMAT while maintaining identical target coverage in both plans.
Highlights
Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) are known to be effective for the treatment of prostate cancer [1,2,3]
The magnetic-resonance image-guided radiation therapy (MR-IGRT) can eliminate or minimize the planning target volume (PTV) margins without an additional imaging dose to the patient [4, 13, 14, 23, 24]. This is considerably beneficial for the administration of radiation therapy to patients with prostate cancer because generally in such cases relatively large PTV margins occur because of large internal organ movement [4, 23]
We demonstrated the potential for significantly lower doses to be delivered to the rectum and bladder in the tri-Co-60 intensity-modulated radiation therapy (IMRT) plans compared with the volumetric-modulated arc therapy (VMAT) plans
Summary
Intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) are known to be effective for the treatment of prostate cancer [1,2,3]. To perform IMRT or VMAT for prostate cancer, considerable margins are generally applied for the generation of the planning target volume (PTV) since the internal motion of the prostate is known to be large 1.5 cm for intrafractional and interfractional motions, respectively) [4, 5] These large PTV margins generally cause overlapping between the target volumes and the neighboring organs at risk (OARs). To deliver prescription doses to the PTVs, these neighboring organs sometimes irradiated by high doses This occasionally results in complications such as rectal bleeding, despite the superior ability of IMRT and VMAT to generate rapid dose fall-off around the target volume [6,7,8]. Adaptive radiation therapy www.impactjournals.com/oncotarget (ART) can reduce the PTV margins effectively; there are a number of practical obstacles to performing ART routinely in the clinic, such as a considerable increase in patient imaging dose and complicated procedures of ART [9,10,11]
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