Dosimetric benefits of hemigland stereotactic body radiotherapy for prostate cancer: implications for focal therapy

作者：Kishan Amar U; Park Sang J; King Christopher R; Roberts Kristofer; Kupelian Patrick A; Steinberg Michael L; Kamrava Mitchell

来源：British Journal of Radiology, 2015, 88(1056): 20150658.

DOI：10.1259/bjr.20150658

Objective: Compared with standard, whole-gland (WG) therapies for prostate cancer, focal approaches may provide equivalent oncologic outcomes with fewer adverse effects. The purpose of this study was to compare organ-at-risk (OAR) dosimetry between hemigland (HG) and WG stereotactic body radiotherapy (SBRT) plans.
Methods: Volumetric-modulated arc radiotherapy-based SBRT plans were designed to treat the left HG, right HG and WG in eight patients, using five fractions of 8 Gy. OARs of interest included the contralateral HG, rectum, urinary bladder, urethra, penile bulb and contralateral neurovascular bundle.
Results: Rectal V-80% (the percentage of a normal structure receiving a dose of 80%) and V-90% were significantly lower with HG plans than with WG plans (median values of 4.4 vs 2.5cm(3) and 2.1 vs 1.1cm(3), respectively, p < 0.05 by Student's t-test). Bladder V-50% was also reduced significantly in HG plans (32.3 vs 17.4cm(3), p < 0.05), with a trend towards reduction of V-100% (3.4 vs 1.3 cm(3), p = 0.09). Urethral maximum dose and mean doses to the penile bulb and contralateral neurovascular bundle were also reduced significantly (42.0 vs 39.7Gy, p < 0.00001; 13.3 vs 9.2Gy, p < 0.05; and 40.2 vs 19.3Gy, p < 0.00001, respectively).
Conclusion: Targeting an HG volume rather than a WG volume when delivering SBRT can offer statistically significant reductions for all OARs. Given the large magnitude of the reduction in dose to these OARs, it is anticipated that HG SBRT could offer a superior toxicity profile when compared with WG SBRT. This is likely to be most relevant in the context of salvaging a local failure after radiation therapy.
Advances in knowledge: The dosimetric feasibility of HG SBRT is demonstrated. When compared with WG SBRT plans, the HG plans demonstrate statistically significant and large magnitude reduction in doses to the rectum, bladder, urethra, penile bulb and contralateral neurovascular bundle, suggesting the possibility of improved toxicity outcomes with HG SBRT. This is likely to be most relevant in the context of salvaging a local failure after radiation therapy.

• 出版日期2015