Department of Radiation Oncology, Chonnam National University Medical School, Gwangju, Korea.
Cancer Res Treat. 2005 Jun;37(3):157-64. doi: 10.4143/crt.2005.37.3.157. Epub 2005 Jun 30.
To assess tumor regression, as determined by pelvic magnetic resonance imaging (MRI), and evaluate the efficacies and toxicities of the interim brachytherapy (BT) modification method, according to tumor regression during multi-fractionated high-dose-rate (HDR) BT for uterine cervical cancer.
Consecutive MRI studies were performed pre-radiotherapy (RT), pre-BT and during interfraction of BT (inter-BT) in 69 patients with cervical cancer. External beam radiotherapy (EBRT) was performed, using a 10 MV X-ray, in daily fraction of 1.8 Gy with 4-fields, 5 d/wk. Radiation was delivered up to 50.4 Gy, with midline shielding at around 30.6 Gy. Of all 69 patients, 50 received modified interim BT after checking the inter-BT MRI. The BT was delivered in two sessions; the first was composed of several 5 Gy fractions to point A, twice weekly, using three channel applicators. According to the three measured orthogonal diameters of the regressed tumor, based on inter-BT MR images, the initial BT plan was modified, with the second session consisting of a few fractions of less than 5 Gy to point A, using a cervical cylinder applicator.
The numbers of patients in FIGO stages Ib, IIa, IIb and IIIb+IVa were 19 (27.5%), 18 (26.1%), 27 (39.2%) and 5 (7.2%), respectively. Our treatment characteristics were comparable to those from the literatures with respect to the biologically effective dose (BED) to point A, rectum and bladder as reference points. In the regression analysis a significant correlation was observed between tumor regression and the cumulative dose to point A on the follow-up MRI. Nearly 80% regression of the initial tumor volume occurred after 30.6 Gy of EBRT, and this increased to 90% after an additional 25 Gy in 5 fractions of BT, which corresponds to 73.6 Gy of cumulative BED(10) to point A. The median total fraction number, and those at the first and second sessions of BT were 8 (5 approximately 10), 5 (3 approximately 7) and 3 (1 approximately 5), respectively. The median follow-up time was 53 months (range, 9 approximately 66 months). The 4-year disease-free survival rate of all patients was 86.8%. Six (8.7%) patients developed pelvic failures, but major late complications developed in only two (2.9%).
Our study shows that effective tumor control, equivalent survival and low rates of major complications can be achieved by modifying the fraction size during BT according to tumor regression, as determined by consecutive MR images. We recommend checking the follow-up MRI at a cumulative BED(10) of around 65 Gy to point A, with the initial BT modified at a final booster BT session.
评估多分割高剂量率（HDR）近距离放射治疗（BT）中根据肿瘤退缩情况调整的盆腔磁共振成像（MRI）肿瘤退缩情况，并评估临时 BT 修正方法的疗效和毒性。
连续对 69 例宫颈癌患者进行放疗前（RT）、BT 前和 BT 期间（BT 间）的 MRI 检查。使用 10MV X 射线进行外照射放疗（EBRT），每天 4 个野，5 天/周，每次 1.8Gy。照射剂量达到 50.4Gy，在 30.6Gy 左右进行中线屏蔽。所有 69 例患者中，50 例在检查 BT 间 MRI 后接受了改良的临时 BT。BT 分两次进行；第一次由几次 5Gy 剂量组成，分次给 A 点，每周两次，使用三个通道施源器。根据 BT 间 MRI 上测量的三个正交直径，基于肿瘤退缩情况，对初始 BT 计划进行修正，第二次由几个小于 5Gy 的分次组成，使用宫颈圆柱施源器给 A 点。
FIGO 分期 Ib、IIa、IIb 和 IIIb+IVa 的患者数量分别为 19 例（27.5%）、18 例（26.1%）、27 例（39.2%）和 5 例（7.2%）。我们的治疗特点在 A 点、直肠和膀胱的生物有效剂量（BED）方面与文献报道相似。在回归分析中，观察到肿瘤退缩与随访 MRI 上 A 点的累积剂量之间存在显著相关性。在接受 30.6Gy 的 EBRT 后，初始肿瘤体积约有 80%发生消退，在接受 25Gy 后进一步增加至 90%，相当于 A 点累积 BED（10）73.6Gy。BT 总分次数中位数为 8（510），第一次和第二次 BT 分次数中位数分别为 5（37）和 3（15）。中位随访时间为 53 个月（966 个月）。所有患者的 4 年无病生存率为 86.8%。6 例（8.7%）患者发生盆腔失败，但仅有 2 例（2.9%）发生严重晚期并发症。
我们的研究表明，通过根据连续 MRI 上的肿瘤退缩情况调整 BT 期间的分次大小，可以实现有效的肿瘤控制、等效生存和较低的严重并发症发生率。我们建议在 A 点累积 BED（10）达到约 65Gy 时进行随访 MRI 检查，并在最终的 BT 增强治疗中修正初始 BT。
