Lewis Shirley, Murthy Vedang, Mahantshetty Umesh, Shrivastava Shyam Kishore
1 Department of Radiation Oncology, Tata Memorial Centre, Parel, Mumbai, Maharashtra, India.
Technol Cancer Res Treat. 2017 Jun;16(3):382-387. doi: 10.1177/1533034617691409. Epub 2017 Feb 7.
Although there is a strong biological rationale to electively treat the pelvic nodes during bladder preservation, its clinical benefit is uncertain. This may be explained by the incidental dose received by the nodal regions when treating the bladder alone. This study was conducted to investigate the doses received by the different pelvic nodal regions when the bladder alone is treated by standard conformal radiotherapy.
The computed tomography data sets of 20 patients with node-negative muscle-invasive bladder cancer treated in a bladder preservation protocol were studied. Patients were originally treated with conformal radiotherapy to the bladder alone. Replanning was done with additional delineation of the pelvic nodal regions namely common iliac (upper and lower), presacral, internal iliac, obturator, and external iliac. Dose volume parameters such as Dmean, Dmax, D100%, D66%, D33%, V40, and V50 to each of the nodal regions were estimated for all patients.
The obturator nodes received the highest dose among all nodal regions. The mean dose received by obturator, external iliac, and internal iliac regions was 59, 45, and 36 Gy, respectively. The dose received by these 3 regions in the full bladder state was 63, 52, and 47 Gy, respectively. The dose received by all other pelvic nodal regions was low and not clinically relevant.
The incidental dose received by obturator and external iliac nodes is clinically significant in bladder-only radiation, possibly enough to influence micrometastatic disease. This may be a reason for the lack of clear benefit seen with nodal irradiation in bladder cancer. Advances in Knowledge: This study highlights that the incidental dose received by obturator and external iliac nodes is clinically significant in bladder-only radiation. The obturator nodes received the highest dose among all nodal regions with mean dose of 59 Gy.
尽管在膀胱保留治疗期间选择性治疗盆腔淋巴结有很强的生物学依据，但其临床益处尚不确定。这可能是由于单独治疗膀胱时淋巴结区域接受的附带剂量所致。本研究旨在调查采用标准适形放疗单独治疗膀胱时不同盆腔淋巴结区域所接受的剂量。
研究了20例按照膀胱保留方案治疗的淋巴结阴性肌层浸润性膀胱癌患者的计算机断层扫描数据集。患者最初仅接受膀胱适形放疗。重新规划时额外勾画了盆腔淋巴结区域，即髂总（上、下）、骶前、髂内、闭孔和髂外淋巴结。为所有患者估计了每个淋巴结区域的剂量体积参数，如平均剂量（Dmean）、最大剂量（Dmax）、接受100%处方剂量的体积（D100%）、接受66%处方剂量的体积（D66%）、接受33%处方剂量的体积（D33%）、接受40 Gy剂量的体积（V40）和接受50 Gy剂量的体积（V50）。
闭孔淋巴结在所有淋巴结区域中接受的剂量最高。闭孔、髂外和髂内区域接受的平均剂量分别为59 Gy、45 Gy和36 Gy。在膀胱充盈状态下，这3个区域接受的剂量分别为63 Gy、52 Gy和47 Gy。所有其他盆腔淋巴结区域接受的剂量较低，无临床意义。
在仅对膀胱进行放疗时，闭孔和髂外淋巴结接受的附带剂量具有临床意义，可能足以影响微转移疾病。这可能是膀胱癌淋巴结照射未显示出明显益处的一个原因。知识进展：本研究强调，在仅对膀胱进行放疗时，闭孔和髂外淋巴结接受的附带剂量具有临床意义。闭孔淋巴结在所有淋巴结区域中接受的剂量最高，平均剂量为59 Gy。
