Abstract
Purpose: The main purpose of this study is to (1) identify the continual diversity between conventional fixed field intensity modulation radiotherapy (IMRT) and RapidArc (RA) for high-risk prostate cancer; and (2) determine potential benefits and drawbacks of using for this type of treatment. Methods: A cohort of 20 prostate cases including prostate, seminal vesicles and pelvic lymph nodes was selected for this study. The primary planning target volume (PTV P ) and boost planning target volume (PTV B ) were contoured. The total prescription dose was 75.6 Gy (45 Gy to PTV P and an additional 21.6 Gy to PTV B ). Two plans were generated for each PTV: multiple 7-fields for IMRT and two arcs for RA. Results: A Sigma index (IMRT: 2.75 ± 0.581; RA: 2.8 ± 0.738) for PTV P and (IMRT: 2.0 ± 0.484; RA: 2.1 ± 0.464) for PTV B indicated similar dose homogeneity inside the PTV. Conformity index (IMRT: 0.96 ± 0.047; RA: 0.95 ± 0.059) for PTV P and (IMRT: 0.97 ± 0.015; RA: 0.96 ± 0.014) for PTV B was comparable for both the techniques. IMRT offered lower mean dose to organ at risks (OARs) compared to RA plans. Normal tissue integral dose in IMRT plan resulted 0.87% lower than RA plans. All the plans displayed significant increase (2.50 times for PTV P and 1.72 for PTB B ) in the average number of necessary monitor units (MUs) with IMRT beam. Treatment delivery time of RA was 2 ‒ 6 minutes shorter than IMRT treatment. Conclusion: For PTV including pelvic lymph nodes, seminal vesicles and prostate, IMRT offered a greater degree of OARs sparing. For PTV including seminal vesicles and prostate, RA with two arcs provided comparable plan with IMRT. RA also improved the treatment efficiency due to smaller number of MUs required.
Highlights
Cancer is the major cause of leading deaths in the 21st century in world with 14.1 million cases and 8.2 million deaths in 2012.1 Among them, prostate cancer stands as important due to risk of secondary malignancies associated with intensity modulation radiation therapy (IMRT) with conventional 3-dimentional conformal radiotherapy (3D-CRT).[2]
We found that monitor units (MUs) was 1542 ± 239 for IMRT plans and 618 ± 71 for RapidArc plans in PTVP
For simple and small PTVs that included prostate and seminal vesicles, RapidArc plans were comparable to those achieved with conventional IMRT plans
Summary
Cancer is the major cause of leading deaths in the 21st century in world with 14.1 million cases and 8.2 million deaths in 2012.1 Among them, prostate cancer stands as important due to risk of secondary malignancies associated with intensity modulation radiation therapy (IMRT) with conventional 3-dimentional conformal radiotherapy (3D-CRT).[2] Among the different technologies adopted to cure the prostate cancer, external radiotherapy is recognized as one of the important treatment options.[3,4] The technology aims to destroy cancer cells by minimal damaging (due to risk of secondary malignancies) to the surrounding normal tissues. IMRT technology for prostate tumor/cancer allows less toxicity in comparison to 3D-CRT.[5] The development of IMRT technique has enabled the delivery of highly conformal
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