St Jude Children's Research Hospital, Radiological Sciences, Memphis, TN 38105, USA.
Int J Radiat Oncol Biol Phys. 2013 Mar 15;85(4):e187-92. doi: 10.1016/j.ijrobp.2012.10.030. Epub 2012 Dec 11.
To estimate the rate of disease control after conformal radiation therapy using reduced clinical target volume (CTV) margins and to determine factors that predict for tumor progression.
Eighty-eight children (median age, 8.5 years; range, 3.2-17.6 years) received conformal or intensity modulated radiation therapy between 1998 and 2009. The study group included those prospectively treated from 1998 to 2003, using a 10-mm CTV, defined as the margin surrounding the solid and cystic tumor targeted to receive the prescription dose of 54 Gy. The CTV margin was subsequently reduced after 2003, yielding 2 groups of patients: those treated with a CTV margin greater than 5 mm (n=26) and those treated with a CTV margin less than or equal to 5 mm (n=62). Disease progression was estimated on the basis of additional variables including sex, race, extent of resection, tumor interventions, target volume margins, and frequency of weekly surveillance magnetic resonance (MR) imaging during radiation therapy. Median follow-up was 5 years.
There was no difference between progression-free survival rates based on CTV margins (>5 mm vs ≤5 mm) at 5 years (88.1% ± 6.3% vs 96.2% ± 4.4% [P=.6386]). There were no differences based on planning target volume (PTV) margins (or combined CTV plus PTV margins). The PTV was systematically reduced from 5 to 3 mm during the time period of the study. Factors predictive of superior progression-free survival included Caucasian race (P=.0175), no requirement for cerebrospinal fluid shunting (P=.0066), and number of surveillance imaging studies during treatment (P=.0216). Patients whose treatment protocol included a higher number of weekly surveillance MR imaging evaluations had a lower rate of tumor progression.
These results suggest that targeted volume reductions for radiation therapy using smaller margins are feasible and safe but require careful monitoring. We are currently investigating the differences in outcome based on host factors to explain the results.
评估使用缩小临床靶区（CTV）边界的适形放疗后疾病控制率，并确定预测肿瘤进展的因素。
88 例儿童（中位年龄 8.5 岁；范围 3.2-17.6 岁）于 1998 年至 2009 年接受适形或调强放疗。研究组包括 1998 年至 2003 年前瞻性治疗的患者，CTV 定义为接受 54Gy 处方剂量的实体和囊性肿瘤靶区周围的 10mm 边界。2003 年后，CTV 边界缩小，分为 2 组患者：CTV 边界大于 5mm（n=26）和 CTV 边界小于或等于 5mm（n=62）。疾病进展基于包括性别、种族、切除范围、肿瘤干预、靶区边界和放疗期间每周磁共振（MR）监测频率等其他变量进行评估。中位随访时间为 5 年。
5 年时，基于 CTV 边界（>5mm 与≤5mm）的无进展生存率无差异（88.1%±6.3%与 96.2%±4.4%[P=.6386]）。基于计划靶区（PTV）边界（或 CTV 加 PTV 边界）无差异。在研究期间，PTV 系统地从 5mm 减少到 3mm。预测无进展生存率更高的因素包括白种人种族（P=.0175）、无需脑脊液分流（P=.0066）和治疗期间的监测影像学研究次数（P=.0216）。治疗方案包括更多每周监测 MR 成像评估的患者肿瘤进展率较低。
这些结果表明，使用较小边界进行放疗的靶区缩小是可行且安全的，但需要仔细监测。我们目前正在研究基于宿主因素的结果差异，以解释结果。
