Pelvic and para-aortic nodal delineation practices and their applicability in rhabdomyosarcoma – A literature review

Abstract

Paediatric pelvic rhabdomyosarcoma (RMS) frequently involves regional lymph nodes, yet no consensus exists for nodal clinical target volume (CTVn) delineation in children. Variations in nodal contours are the leading cause of unacceptable plans in the current Frontline and Relapsed Rhabdomyosarcoma (FaR-RMS) trial, underscoring the need for guidance. A PubMed search identified studies on nodal distribution and CTVn definition for pelvic, para-aortic, and inguinal regions, using terms related to lymph-node mapping and radiotherapy planning. Thirty-three English-language papers met the inclusion criteria; data on anatomic spread, recommended margins, and dosimetric consequences were extracted. None of the studies included paediatric patients; the lowest reported age was 25 years old. Para-aortic mapping revealed dominant involvement of the left para-aortic and aortocaval regions, favouring asymmetric contours that spare the right para-caval space above L1–L2. Hybrid atlases improved nodal-center coverage to 98% while reducing duodenal dose. For iliac chains, symmetrical expansions of 7–10 mm around major vessels achieved ≈ 95% nodal coverage, whereas presacral and obturator nodes required 10–22 mm strips and bony landmarks. Studies describing inguinal lymph nodes showed 98% of the nodes in the anteromedial and anterior quadrants superior to the pubic symphysis, supporting compartmental delineation, bounded laterally by the iliopsoas and posteriorly by the femoral triangle. The adult-derived recommendations compiled here will provide the basis for delineation guidelines and a supporting atlas for use within the FaR-RMS trial. Prospective radiotherapy quality assurance will validate contour adequacy and inform future refinement.