Dosimetric evaluation of inclusion of proximal seminal vesicle in target volume in low-risk prostate cancer treated with stereotactic body radiotherapy

Authors : Ela DELİKGÖZ SOYKUT, Hatice TATAROĞLU

Pages : 253-260

Doi:10.38053/acmj.1320219

View : 52 | Download : 52

Publication Date : 2023-07-28

Article Type : Research Paper

Abstract :Aims: Ultra hypofractionation using stereotactic body radiotherapy insert ignore into journalissuearticles values(SBRT); for low-risk PCa is considered a viable treatment option. The target volume for ultra hypofractionated RT was determined as prostate and/or proximal seminal vesicles; however, there are no clear guidelines on when to add a proximal seminal vesicle to the target volume. We aimed to dosimetrically assess the effect of inclusion of the proximal seminal vesicle in the planning target volume insert ignore into journalissuearticles values(PTV); on the dose distribution of organ at risk insert ignore into journalissuearticles values(OAR); when SBRT is administered to patients with low-risk PCa. Methods: Low-risk PCa cases who underwent SBRT with CyberKnife were retrospectively screened, and 20 random cases were included. The contours of OARs and target volumes were checked as recommended in international contouring atlases by the same radiation oncologist. Two treatment plans by determining two different PTV insert ignore into journalissuearticles values(prostate alone in plan 1 and prostate with proximal seminal vesicles in plan 2); were made by the same specialist physicist. 5×7.25 Gy was chosen as the dose schedule defined for both plans. Results: Regarding coverage, homogeneity index, and new conformity index insert ignore into journalissuearticles values(nCI);, there was no significant difference between the two plans insert ignore into journalissuearticles values(p=0.397, p=0.452, p=0.225);. The plan 2 had a greater PTV Dmax insert ignore into journalissuearticles values(p<0.001);. There was better conformity index at plan 1, as well as lower monitor unit and beam on time insert ignore into journalissuearticles values(p<0.05);. The plan 1 had statistically lower values for each treatment parameter assessed for bladder insert ignore into journalissuearticles values(p<0.05);. The treatment parameters evaluated for the rectum were statistically lower in the plan 1, except for V32.625 insert ignore into journalissuearticles values(p<0.05);. The plan 1 was statistically better in terms of V29.5 for the penile bulb and V37.5 and V38 for neurovascular bundles insert ignore into journalissuearticles values(p<0.05);. There was no significant difference between the two plans in terms of femoral heads and bowel insert ignore into journalissuearticles values(p=0.180, p=0.209, p=0.398, p=0.726, p=0.053, p=0.068);. In addition, regardless of plan type, a majority of treatment parameters for bladder were statistically significantly affected in plans with a PTV volume greater than 100 cc insert ignore into journalissuearticles values(p<0.05);. Conclusion: In low-risk PCa, inclusion of the proximal seminal vesicle in the target volume may be overlooked as quantitatively insignificant increases in high-dose OAR volumes as they do not exceed dose constraints in routine clinical practice, and these high-dose OAR volumes are likely to be important in the development of toxicity. We recommend that special attention be paid to the high doses exposed in OARs in low-risk PCa. In addition, it should be kept in mind that bladder toxicity may increase with increasing PTV volume, especially above 100 cc.
Keywords : Low risk, prostate cancer, prostate, seminal vesicle, stereotactic body radiotherapy, target volume