Borghetti Paolo, Pedretti Sara, Spiazzi Luigi, Avitabile Rossella, Urpis Mauro, Foscarini Federica, Tesini Giulia, Trevisan Francesca, Ghirardelli Paolo, Pandini Sara Angela, Triggiani Luca, Magrini Stefano Maria, Buglione Michela
Radiation Oncology Department, University and Spedali Civili Brescia, P.le Spedali Civili 1, Brescia, Italy.
Medical Physics Department, Spedali Civili Brescia, P.le Spedali Civili 1, Brescia, Italy.
Radiat Oncol. 2016 Apr 19;11:59. doi: 10.1186/s13014-016-0634-6.
To compare and evaluate the possible advantages related to the use of VMAT and helical IMRT and two different modalities of boost delivering, adjuvant stereotactic boost (SRS) or simultaneous integrated boost (SIB), in the treatment of brain metastasis (BM) in RPA classes I-II patients.
Ten patients were treated with helical IMRT, 5 of them with SRS after whole brain radiotherapy (WBRT) and 5 with SIB. MRI co-registration with planning CT was mandatory and prescribed doses were 30 Gy in 10 fractions (fr) for WBRT and 15Gy/1fr or 45Gy/10fr in SRS or SIB, respectively. For each patient, 4 "treatment plans" (VMAT SRS and SIB, helical IMRT SRS and SIB) were calculated and accepted if PTV boost was included in 95 % isodose and dose constraints of the main organs at risk were respected without major deviations. Homogeneity Index (HI), Conformal Index (CI) and Conformal Number (CN) were considered to compare the different plans. Moreover, time of treatment delivery was calculated and considered in the analysis.
Volume of brain metastasis ranged between 1.43 and 51.01 cc (mean 12.89 ± 6.37 ml) and 3 patients had double lesions. V95% resulted over 95 % in the average for each kind of technique, but the "target coverage" was inadequate for VMAT planning with two sites. The HI resulted close to the ideal value of zero in all cases; VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS showed mean CI of 2.15, 2.10, 2.44 and 1.66, respectively (optimal range: 1.5-2.0). Helical IMRT-SRS was related to the best and reliable finding of CN (0.66). The mean of treatment time was 210 s, 467 s, 440 s, 1598 s, respectively, for VMAT-SIB, VMAT-SRS, Helical IMRT-SIB and Helical IMRT-SRS.
This dosimetric comparison show that helical IMRT obtain better target coverage and respect of CI and CN; VMAT could be acceptable in solitary metastasis. SIB modality can be considered as a good choice for clinical and logistic compliance; literature's preliminary data are confirming also a radiobiological benefit for SIB. Helical IMRT-SRS seems less effective for the long time of treatment compared to other techniques.
比较和评估容积调强弧形放疗（VMAT）与螺旋调强适形放疗（IMRT）以及两种不同的加量方式，即辅助立体定向加量（SRS）或同步整合加量（SIB），在治疗RPA I-II级脑转移瘤（BM）患者中的潜在优势。
10例患者接受螺旋IMRT治疗，其中5例在全脑放疗（WBRT）后接受SRS，5例接受SIB。必须进行MRI与计划CT的配准，WBRT的处方剂量为30 Gy，分10次（f），SRS或SIB的剂量分别为15Gy/1f或45Gy/10f。对于每位患者，计算4种“治疗计划”（VMAT SRS和SIB、螺旋IMRT SRS和SIB），如果计划靶区（PTV）加量包含在95%等剂量线内且主要危及器官的剂量限制得到遵守且无重大偏差，则计划被接受。采用均匀性指数（HI）、适形指数（CI）和适形数（CN）来比较不同的计划。此外，计算并在分析中考虑治疗时间。
脑转移瘤体积在1.43至51.01 cc之间（平均12.89±6.37 ml），3例患者有双发病灶。每种技术的V95%平均超过95%，但VMAT计划在两个部位的“靶区覆盖”不足。所有情况下HI均接近理想值零；VMAT-SIB、VMAT-SRS、螺旋IMRT-SIB和螺旋IMRT-SRS的平均CI分别为2.15、2.10、2.44和1.66（最佳范围：1.5-2.0）。螺旋IMRT-SRS的CN值最佳且可靠（0.66）。VMAT-SIB、VMAT-SRS、螺旋IMRT-SIB和螺旋IMRT-SRS的平均治疗时间分别为210秒、467秒、440秒、1598秒。
该剂量学比较表明，螺旋IMRT能获得更好的靶区覆盖以及对CI和CN的遵守；VMAT在孤立转移瘤中可接受。SIB方式可被视为临床和后勤依从性方面的良好选择；文献中的初步数据也证实了SIB在放射生物学方面的益处。与其他技术相比，螺旋IMRT-SRS的治疗时间似乎较长，效果较差。
