Large topographic variability of upper abdominal lymphatics and the consequences for radiation treatment planning.
OBJECTIVE
Inclusion of regional lymph nodes usually is indicated when treating upper gastrointestinal malignancies. Lymphatics follow the large vessels of this region. Vascular variability with consequences for planning treatment volume (PTV) was studied.


METHODS
Upper abdominal metric relationship of the vascular origins was analysed in CT scans in 104 patients to estimate its influence on PTV variability. PTV volumes were calculated based on these. Additionally, the PTV size of 3D plans of 34 patients with pancreatic adenocarcinoma (PDAC) was analysed depending on different PTV definitions.


RESULTS
Vascular origin varied most for the inferior mesenteric artery (IMA) with substantial PTV size differences. Volumetric variability was analysed for PDAC (IMA versus renal hilum as caudal margin). Additional PTV for IMA was < 100 cc (median) but ranged up to 350 cc in CT (100-199 ml in 14/34 and > 200 ml in 3/34 patients). Data from treatment planning confirmed this observation.


CONCLUSIONS
Considerable vascular and lymphatic variability obliges to base PTV on the individual vascular anatomy. For most patients the caudal PTV margin for PDAC can safely be set at the IMA. But PTV should be restricted when the additional volume would lead to a significant increase to avoid haematotoxicity from concomitant gemcitabine which is proportional with PTV size. The risk of kidney toxicity is also subject to PTV expansion in the caudal direction.
Brunner
Thomas B
TB
Department of Radiation Oncology, University Hospitals of Erlangen, Erlangen, Germany. tb@strahlen.med.uni-erlangen.de
Baum
Ulrich
U
Grabenbauer
Gerhard G
GG
Sauer
Rolf
R
Lambrecht
Ulrike
U
D000230:Adenocarcinoma / Q000532:radiotherapy*; D003841:Deoxycytidine / Q000009:adverse effects / Q000031:analogs & derivatives / Q000627:therapeutic use; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008198:Lymph Nodes / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D042601:Lymphatic Vessels / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D008297:Male; D010190:Pancreatic Neoplasms / Q000532:radiotherapy*; D011838:Radiation-Sensitizing Agents / Q000009:adverse effects / Q000627:therapeutic use; D011860:Radiography, Abdominal; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D000093542:Gemcitabine
D011838:Radiation-Sensitizing Agents; D003841:Deoxycytidine; D000093542:Gemcitabine