Anbumani Surega, Palled Siddanna R, Prabhakar Girish S, Nambiraj N Arunai, Pichandi Anchineyan
HCG-Bangalore Institute of Oncology, Bangalore, India.
Kidwai Memorial Institute of Oncology, Bangalore, India.
Rep Pract Oncol Radiother. 2012 Jun 15;17(4):200-6. doi: 10.1016/j.rpor.2012.04.002. eCollection 2012.
To investigate the feasibility of using External Beam radiotherapy for accelerated partial breast irradiation by a comparative tumour and normal tissue dose volume analysis with that of high dose rate interstitial brachytherapy.
Accelerated Partial Breast Irradiation (APBI) is more clinically appealing because of the reduced treatment course duration and the irradiated area. Brachytherapy application is more dependent on the clinician's expertise when it is practised free hand without image guidance and a template. It happens to be an invasive procedure with the use of local anaesthesia which adds patient discomfort apart from its cost compared to External Beam Radiotherapy. But APBI with brachytherapy is more commonly practised procedure compared to EBRT owing to its previous reults. Hence in this research study, we intend to explore the use of EBRT with the radiobiological corrections for APBI in the place of brachytherapy. It is done as a dosimetric comparison of Brachytherapy treatment plans with that of EBRT plans.
The computed tomography images of 15 patients undergoing ISBT planning were simulated with conformal photon fields. Various dose volume parameters of each structure were obtained from the DVH generated in the brachytherapy and the simulated external beam planning which can correlate well with the late toxicity. The plan quality indices such as conformity index and homogeneity index for the target volume were computed from the dosimetric factors. The statistical p values for CI, HI and normal tissue dosimetric parameters were calculated and the confidence levels achievable were analysed. The dose prescribed in brachytherapy was 3400cGy in ten fractions. The equivalent prescription dose for the external beam radiotherapy planning was 3000cGy in five fractions applied with radiobiological correction.
All the fifteen patients were with complete lung data and six were with left sided tumours having complete cardiac data. The lung dosimetry data and the cardiac dosimetry data of the patients were studied. Lower percentages of lung and cardiac V 20 and V 5 volumes were obtained with conformal planning. The conformity of radiation dose to the tumour volume was akin to the interstitial brachytherapy planning. Moreover the external beam planning resulted in more homogenous dose distribution. For the sampled population, the statistical analysis showed a confidence level of 95% for using EBRT as an alternate to multi catheter ISBT.
The EBRT planning for Accelerated Partial Breast Irradiation was found to be technically feasible in the institution where the interstitial brachytherapy happens to be the only available technique as evident from the dose volume parameters and the statistical analysis.
通过对肿瘤和正常组织剂量体积分析，并与高剂量率组织间近距离放射治疗进行比较，研究采用外照射放疗进行加速部分乳腺照射的可行性。
加速部分乳腺照射（APBI）因治疗疗程缩短和照射面积减小而在临床上更具吸引力。当徒手操作且无图像引导和模板时，近距离放射治疗的应用更依赖临床医生的专业技能。与外照射放疗相比，它是一种侵入性操作，需要局部麻醉，这除了成本外还增加了患者的不适。但由于以往的结果，与外照射放疗相比，APBI联合近距离放射治疗是更常用的方法。因此，在本研究中，我们打算探索使用经过放射生物学校正的外照射放疗来替代近距离放射治疗进行APBI。这是通过将近距离放射治疗计划与外照射放疗计划进行剂量学比较来完成的。
对15例接受组织间近距离放射治疗计划的患者的计算机断层扫描图像进行适形光子野模拟。从近距离放射治疗和模拟外照射放疗生成的剂量体积直方图（DVH）中获取每个结构的各种剂量体积参数，这些参数与晚期毒性有很好的相关性。根据剂量学因素计算靶区的计划质量指标，如适形指数和均匀性指数。计算适形指数、均匀性指数和正常组织剂量学参数的统计p值，并分析可达到的置信水平。近距离放射治疗规定的剂量为3400cGy，分10次给予。外照射放疗计划的等效处方剂量为3000cGy，分5次给予，并进行放射生物学校正。
15例患者均有完整的肺部数据，6例左侧肿瘤患者有完整的心脏数据。研究了患者的肺部剂量学数据和心脏剂量学数据。适形计划获得的肺部和心脏V20及V5体积百分比更低。放射剂量与肿瘤体积的适形性类似于组织间近距离放射治疗计划。此外，外照射放疗计划导致剂量分布更均匀。对于抽样人群，统计分析表明使用外照射放疗替代多导管组织间近距离放射治疗的置信水平为95%。
从剂量体积参数和统计分析来看，在组织间近距离放射治疗是唯一可用技术的机构中，加速部分乳腺照射的外照射放疗计划在技术上是可行的。
