使用¹³¹Cs和¹²⁵I进行前列腺永久性植入近距离放射治疗时前列腺和尿道的剂量学及生物有效剂量参数比较

Comparison of dosimetric and biologic effective dose parameters for prostate and urethra using 131 Cs and 125 I for prostate permanent implant brachytherapy.

作者信息

Sahgal Arjun, Jabbari Siavash, Chen Josephine, Pickett Barbie, Roach Mack, Weinberg Vivian, Hsu I-Chow, Pouliot Jean

机构信息

Department of Radiation Oncology, University of California, San Francisco, School of Medicine, San Francisco, CA94143, USA.

出版信息

Int J Radiat Oncol Biol Phys. 2008 Sep 1;72(1):247-54. doi: 10.1016/j.ijrobp.2008.05.013.

DOI:10.1016/j.ijrobp.2008.05.013

PMID:18722275

Abstract

PURPOSE

To compare the urethral and prostate absolute and biologic effective doses (BEDs) for 131 Cs and 125 I prostate permanent implant brachytherapy (PPI).

METHODS AND MATERIALS

Eight previously implanted manually planned 125 I PPI patients were replanned manually with 131 Cs, and re-planned using Inverse Planning Simulated Annealing. 131 Cs activity and the prescribed dose (115 Gy) were determined from that recommended by IsoRay. The BED was calculated for the prostate and urethra using an alpha/beta ratio of 2 and was also calculated for the prostate using an alpha/beta ratio of 6 and a urethral alpha/beta ratio of 2. The primary endpoints of this study were the prostate D90 BED (pD90BED) and urethral D30 BED normalized to the maximal potential prostate D90 BED (nuD30BED).

RESULTS

The manual plan comparison (alpha/beta = 2) yielded no significant difference in the prostate D90 BED (median, 192 Gy2 for both isotopes). No significant difference was observed for the nuD30BED (median, 199 Gy2 and 202 Gy2 for 125 I and 131 Cs, respectively). For the inverse planning simulated annealing plan comparisons (alpha/beta = 2), the prostate D90 BED was significantly lower with 131 Cs than with 125 I (median, 177 Gy2 vs. 187 Gy2, respectively; p = 0.01). However, the nuD30BED was significantly greater with 131 Cs than with 125 I (median, 192 Gy2 vs. 189 Gy2, respectively; p = 0.01). Both the manual and the inverse planning simulated annealing plans resulted in a significantly lower prostate D90 BED (p = 0.01) and significantly greater nuD30BED for 131 Cs (p = 0.01), compared with 125 I, when the prostate alpha/beta ratio was 6 and the urethral alpha/beta ratio was 2.

CONCLUSION

This report highlights the controversy in comparing the dose to both the prostate and the organs at risk with different radionuclides.

摘要

目的

比较¹³¹Cs和¹²⁵I前列腺永久性植入近距离放射治疗（PPI）中尿道和前列腺的绝对剂量及生物等效剂量（BED）。

方法和材料

对8例先前接受手动计划的¹²⁵I PPI患者进行¹³¹Cs手动重新计划，并使用逆向计划模拟退火算法重新计划。¹³¹Cs活度和处方剂量（115 Gy）根据IsoRay推荐的值确定。使用α/β比值为2计算前列腺和尿道的BED，还使用α/β比值为6计算前列腺的BED以及α/β比值为2计算尿道的BED。本研究的主要终点是前列腺D90生物等效剂量（pD90BED）和归一化至最大潜在前列腺D90生物等效剂量的尿道D30生物等效剂量（nuD30BED）。

结果

手动计划比较（α/β = 2）显示前列腺D90 BED无显著差异（两种同位素的中位数均为192 Gy²）。nuD30BED也无显著差异（¹²⁵I和¹³¹Cs的中位数分别为199 Gy²和202 Gy²）。对于逆向计划模拟退火计划比较（α/β = 2），¹³¹Cs的前列腺D90 BED显著低于¹²⁵I（中位数分别为177 Gy²和187 Gy²；p = 0.01）。然而，¹³¹Cs的nuD30BED显著高于¹²⁵I（中位数分别为192 Gy²和189 Gy²；p = 0.01）。当前列腺α/β比值为6且尿道α/β比值为2时，与¹²⁵I相比，手动计划和逆向计划模拟退火计划均导致¹³¹Cs的前列腺D90 BED显著降低（p = 0.01）且nuD30BED显著升高（p = 0.01）。