Gloi Aime, McCourt Steve, Buchanan Robert, Goetller Andrea, Zuge Corrie, Balzoa Paula, Cooley Greg
Department of Radiation Oncology, St. Vincent, Green Bay, WI 54301, USA.
Med Dosim. 2009 Fall;34(3):207-13. doi: 10.1016/j.meddos.2008.08.003. Epub 2008 Sep 21.
The objective of this work is to evaluate biological models and dose homogeneity in a new partial breast irradiation method, the MammoSite RTS. The study is based on 11 patients who received the therapy. For each patient, we determined the dose volume distribution delivered to the breast. Based on these data, we estimate some important biological parameters. Eleven patients with early-stage, invasive, ductal breast cancer were treated using MammoSite RTS brachytherapy, which delivers radiation through a balloon placed in the lumpectomy bed. The radiation was provided by an Iridium-192 source, and 340 cGy were delivered per fraction twice daily. We calculated some commonly used dosimetric parameters, and evaluated the biological parameters tumor control probability (TCP) and normal tissue complication probability (NTCP). We also looked for correlations among these parameters. The average equivalent uniform dose (EUD), NTCP, and TCP were 43.66 Gy, 47.95%, and 91.78%, respectively. The coefficient of variation (CV) among the patients was very low for all 3 parameters. Two dose homogeneity indices (DHI and the S-index) are strongly correlated (r = -0.815). The area under the dose-volume histogram (DVH) and the treatment volume (TXV) also showed a strong correlation (r = 0.995, p < 0.0001). A simplified logit Poisson-EUD model is suitable for determining NTCP and TCP. Other factors such as the area under the DVH and dose homogeneity indices are also useful in planning radiotherapy treatments for early breast cancer.
本研究的目的是评估一种新的部分乳腺照射方法——MammoSite RTS中的生物学模型和剂量均匀性。该研究基于11例接受该治疗的患者。对于每位患者，我们确定了乳腺所接受的剂量体积分布。基于这些数据，我们估算了一些重要的生物学参数。11例早期浸润性导管乳腺癌患者接受了MammoSite RTS近距离放射治疗，该治疗通过置于乳房肿瘤切除术后腔隙中的球囊进行放射。放射源为铱-192，每天两次，每次分割剂量为340 cGy。我们计算了一些常用的剂量学参数，并评估了生物学参数肿瘤控制概率（TCP）和正常组织并发症概率（NTCP）。我们还研究了这些参数之间的相关性。平均等效均匀剂量（EUD）、NTCP和TCP分别为43.66 Gy、47.95%和91.78%。所有这3个参数在患者之间的变异系数（CV）都非常低。两个剂量均匀性指数（DHI和S指数）高度相关（r = -0.815）。剂量体积直方图（DVH）下的面积与治疗体积（TXV）也显示出高度相关性（r = 0.995，p < 0.0001）。一个简化的logit泊松-EUD模型适用于确定NTCP和TCP。其他因素，如DVH下的面积和剂量均匀性指数，在早期乳腺癌放疗计划中也很有用。
