Contouring inguinal and femoral nodes; how much margin is needed around the vessels?

Pract Radiat Oncol. 2012 Oct-Dec;2(4):274-278. doi: 10.1016/j.prro.2011.12.005. Epub 2012 Feb 6.

Abstract

Purpose: To determine the optimal margin needed around the femoral vessels for appropriate inguinofemoral lymph node coverage and to propose guidelines defined by anatomic boundaries for clinical target volume delineation.

Methods and materials: Twenty-two patients with pelvic malignancies and involved inguinal lymph nodes treated with conformal radiation therapy were selected. Lymph nodes were considered positive if they were pathologically malignant by biopsy, had 1(8)F-fluorodeoxyglucose avidity on positron emission tomography or measured ≥1.5 cm on computed tomographic scan. We measured distance from the center of node(s) to the edge of the nearest femoral vessel.

Results: There were 52 total positive inguinal nodes among 22 patients. Relative to the femoral vessels, the location of the nodes were 51.9% anteromedial, 21.2% anterior, 11.5% anterolateral, 9.6% medial, 1.9% posterior, and 3.9% lateral. To cover ≥90% disease, the margins needed around the nearest femoral vessel were anteromedial ≥35 mm, anterior ≥23 mm, anterolateral ≥25 mm, medial ≥22 mm, posterior ≥9 mm, and ≥32 mm lateral. The corresponding anatomic boundaries were the following: laterally, medial border of the iliopsoas; medially, lateral border of adductor longus or medial end of pectineus; posteriorly, iliopsoas muscle laterally and anterior aspect of the pectineus muscle; medially and anteriorly, the anterior edge of the sartorius muscle. Most of the macroscopic nodes were medial or anteromedial to the femoral vessels. No patient had involved posterior or lateral nodes alone without positive nodes in the anterior or anteromedial positions.

Conclusions: Circumferential margins around femoral vessels required to adequately cover this nodal region were >2 cm in most directions. Contouring the inguinal lymph nodes as a compartment defined by the anatomic landmarks suggested above may be more reproducible. Physicians should exercise caution in extrapolating pelvic nodal contouring guidelines to inguinal lymph nodal contouring.