Cavey Matthew L, Bayouth John E, Endres Eugene J, Pena John M, Colman Martin, Hatch Sandra
Department of Radiation Oncology, University of Texas Medical Branch, Galveston, TX 77555-0711, USA.
Med Dosim. 2005 Summer;30(2):107-16. doi: 10.1016/j.meddos.2005.02.002.
Three recently published randomized trials have shown a survival benefit to postoperative radiation therapy when the internal mammary chain (IMC), supraclavicular (SCV), and axillary lymphatics are treated. When treating the IMC, techniques that minimize dose to the heart and lungs may be utilized to prevent excess morbidity and mortality and achieve the survival benefit reported. The purpose of this study was to dosimetrically compare forward-planned intensity-modulated radiation therapy (fIMRT) with conventional techniques for comprehensive irradiation of the chest wall and regional lymphatics. For irradiation of the chest wall and IMC, 3 treatment plans, (1) fIMRT, (2) partially-wide tangent (PWT) fields, and (3) a photon-electron (PE) technique, were compared for 12 patients previously treated at our institution with fIMRT to the left chest wall and regional lymphatics. Additionally, the SCV and infraclavicular lymphatics were irradiated and 4 methods were compared: 2 with anterior fields only (dose prescribed to 3 and 5 cm [SC3cm, SC5cm]) and 2 with anterior and posterior fields (fIMRT, 3DCRT). Each patient was planned to receive 50 Gy in 25 fractions. Regions of interest (ROIs) created for each patient included chest wall (CW) planning target volume (PTV), IMC PTV, and SCV PTV. Additionally, the following organs at risk (OAR) volumes were created: contralateral breast, heart, and lungs. For each plan and ROI, target volume coverage (V(95-107)) and dose homogeneity (D(95-5)) were evaluated. Additionally, the mean OAR dose and normal tissue complication probability (NTCP) were computed. For irradiation of the CW, target volume coverage and dose homogeneity were improved for the fIMRT technique as compared to PE (p < 0.001, p = 0.023, respectively). Similar improvements were seen with respect to IMC PTV (p = 0.012, p = 0.064). These dosimetric parameters were also improved as compared to PWT, but not to the same extent (p = 0.011, p = 0.095 for CW PTV, and p = 0.164, p > 0.2 for IMC PTV). The PE technique resulted in the lowest heart V30, although this difference was not significant (p > 0.2). The NTCP values for excess cardiac mortality for fIMRT and PE were equivalent (1.9%) and lower than with PWT (2.8%, p > 0.2). The fIMRT technique was able to reduce heart dose and NTCP for each patient as compared to PWT. When comparing the anterior field techniques of treating SCV PTV, prescribing dose to 5 cm resulted in a improved V50 (p = 0.089). However, when compared to fIMRT, the SC3cm and SC5cm had inferior target volume coverage (p = 0.055, p = 0.014) and significantly greater dose heterogeneity (p = 0.031, p = 0.043). The addition of a posterior field increased the volume of lung receiving 40 and 50 Gy, but not significantly (p > 0.2). For complex breast treatments that irradiate the chest wall, IMC, and SCV, fIMRT resulted in improved dose homogeneity and target volume coverage as compared to conventional techniques. Furthermore, the dosimetric gains in target volume coverage with fIMRT came at no significant increase in dose to OAR. The fIMRT technique demonstrated the ability to maintain the advantage of each of the other 2 techniques: reducing the dose to OARs, as with PE, and providing superior target volume coverage, as with PWT.
最近发表的三项随机试验表明，当对胸骨旁淋巴结链（IMC）、锁骨上淋巴结（SCV）和腋窝淋巴管进行治疗时，术后放射治疗可带来生存获益。在治疗IMC时，可采用将心脏和肺部剂量降至最低的技术，以预防过高的发病率和死亡率，并实现所报道的生存获益。本研究的目的是通过剂量学方法，将正向计划调强放疗（fIMRT）与用于胸壁和区域淋巴结综合照射的传统技术进行比较。对于胸壁和IMC的照射，比较了三种治疗计划：（1）fIMRT，（2）部分宽切线（PWT）野，（3）光子 - 电子（PE）技术，针对12例之前在本机构接受过左侧胸壁和区域淋巴结fIMRT治疗的患者。此外，对SCV和锁骨下淋巴结进行了照射，并比较了四种方法：2种仅使用前野（处方剂量分别为3 cm和5 cm [SC3cm，SC5cm]），2种使用前野和后野（fIMRT，3DCRT）。每位患者计划接受25次分割照射，总剂量50 Gy。为每位患者创建的感兴趣区域（ROI）包括胸壁（CW）计划靶体积（PTV）、IMC PTV和SCV PTV。此外，还创建了以下危及器官（OAR）体积：对侧乳腺、心脏和肺。对于每个计划和ROI，评估靶体积覆盖率（V(95 - 107)）和剂量均匀性（D(95 - 5)）。此外，计算了OAR的平均剂量和正常组织并发症概率（NTCP）。对于CW的照射，与PE相比，fIMRT技术的靶体积覆盖率和剂量均匀性得到改善（分别为p < 0.001，p = 0.023）。IMC PTV方面也有类似改善（p = 0.012，p = 0.064）。与PWT相比，这些剂量学参数也有所改善，但程度不同（CW PTV为p = 0.011，p = 0.095；IMC PTV为p = 0.164，p > 0.2）。PE技术导致心脏V30最低，尽管差异不显著（p > 0.2）。fIMRT和PE的心脏超额死亡率NTCP值相当（1.9%），低于PWT（2.8%，p > 0.2）。与PWT相比，fIMRT技术能够降低每位患者的心脏剂量和NTCP。在比较治疗SCV PTV的前野技术时，处方剂量为5 cm可改善V50（p = 0.089）。然而，与fIMRT相比，SC3cm和SC5cm的靶体积覆盖率较差（p = 0.055，p = 0.014），且剂量不均匀性显著更大（p = 0.031，p = 0.043）。添加后野会增加接受40 Gy和50 Gy照射的肺体积，但不显著（p > 0.2）。对于照射胸壁、IMC和SCV的复杂乳腺治疗，与传统技术相比，fIMRT可改善剂量均匀性和靶体积覆盖率。此外，fIMRT在靶体积覆盖率方面的剂量学优势并未导致OAR剂量显著增加。fIMRT技术展示了保持其他两种技术各自优势的能力：如PE一样降低OAR剂量，如PWT一样提供更好的靶体积覆盖率。
