Koontz Bridget F, Das Shiva, Temple Kathy, Bynum Sigrun, Catalano Suzanne, Koontz Jason I, Montana Gustavo S, Oleson James R
Departments of Radiation Oncology and Medicine, Duke University Medical Center, Durham, NC 27710, USA.
Med Dosim. 2009 Fall;34(3):256-60. doi: 10.1016/j.meddos.2008.10.005. Epub 2008 Dec 3.
Adjuvant radiotherapy for locally advanced prostate cancer improves biochemical and clinical disease-free survival. While comparisons in intact prostate cancer show a benefit for intensity modulated radiation therapy (IMRT) over 3D conformal planning, this has not been studied for post-prostatectomy radiotherapy (RT). This study compares normal tissue and target dosimetry and radiobiological modeling of IMRT vs. 3D conformal planning in the postoperative setting. 3D conformal plans were designed for 15 patients who had been treated with IMRT planning for salvage post-prostatectomy RT. The same computed tomography (CT) and target/normal structure contours, as well as prescription dose, was used for both IMRT and 3D plans. Normal tissue complication probabilities (NTCPs) were calculated based on the dose given to the bladder and rectum by both plans. Dose-volume histogram and NTCP data were compared by paired t-test. Bladder and rectal sparing were improved with IMRT planning compared to 3D conformal planning. The volume of the bladder receiving at least 75% (V75) and 50% (V50) of the dose was significantly reduced by 28% and 17%, respectively (p = 0.002 and 0.037). Rectal dose was similarly reduced, V75 by 33% and V50 by 17% (p = 0.001 and 0.004). While there was no difference in the volume of rectum receiving at least 65 Gy (V65), IMRT planning significant reduced the volume receiving 40 Gy or more (V40, p = 0.009). Bladder V40 and V65 were not significantly different between planning modalities. Despite these dosimetric differences, there was no significant difference in the NTCP for either bladder or rectal injury. IMRT planning reduces the volume of bladder and rectum receiving high doses during post-prostatectomy RT. Because of relatively low doses given to the bladder and rectum, there was no statistically significant improvement in NTCP between the 3D conformal and IMRT plans.
局部晚期前列腺癌的辅助放疗可改善生化无病生存率和临床无病生存率。虽然在完整前列腺癌的比较中显示，调强放射治疗（IMRT）优于三维适形放疗，但前列腺切除术后放疗（RT）尚未对此进行研究。本研究比较了术后IMRT与三维适形放疗的正常组织和靶区剂量测定以及放射生物学模型。为15例接受过IMRT计划的前列腺切除术后挽救性放疗患者设计了三维适形计划。IMRT和三维计划使用相同的计算机断层扫描（CT）以及靶区/正常结构轮廓和处方剂量。根据两种计划给予膀胱和直肠的剂量计算正常组织并发症概率（NTCPs）。通过配对t检验比较剂量体积直方图和NTCP数据。与三维适形放疗相比，IMRT计划改善了膀胱和直肠的保护。接受至少75%（V75）和50%（V50）剂量的膀胱体积分别显著减少了28%和17%（p = 0.002和0.037）。直肠剂量也有类似减少，V75减少33%，V50减少17%（p = 0.001和0.004）。虽然接受至少65 Gy（V65）的直肠体积没有差异，但IMRT计划显著减少了接受40 Gy或更高剂量的体积（V40，p = 0.009）。两种计划方式之间膀胱V40和V65没有显著差异。尽管存在这些剂量差异，但膀胱或直肠损伤的NTCP没有显著差异。IMRT计划减少了前列腺切除术后放疗期间接受高剂量的膀胱和直肠体积。由于给予膀胱和直肠的剂量相对较低，三维适形计划和IMRT计划之间的NTCP没有统计学上的显著改善。
