Anatomic Distribution of Fluorodeoxyglucose-Avid Para-aortic Lymph Nodes in Patients With Cervical Cancer

Abstract

Summary This study presents a map of PET-positive paraaortic nodes (PAN) in cervical cancer. Available information about the location of PAN metastases in cervical cancer is not adequately detailed to guide treatment planning for highly conformal radiation therapy. Our population based atlas outlines the spatial distribution of these lymph nodes to facilitate target delineation and treatment planning. Suggested clinical target volume contours are included, which provide coverage of PAN nodes for the treatment of cervical cancer. Purpose Conformal treatment of paraaortic lymph nodes (PAN) in cervical cancer allows dose escalation and reduces normal tissue toxicity. Currently, data documenting the precise location of involved PAN are lacking. We define the spatial distribution of this high-risk nodal volume by analyzing FDG-avid lymph nodes (LNs) on PET/CT scans in patients with cervical cancer. Materials/Methods We identified 72 PANs on pretreatment PET/CT of 30 patients with newly-diagnosed stage IB-IVA cervical cancer treated with definitive chemoradiation. LNs were classified as left-lateral paraaortic (LPA), aortocaval (AC), right paracaval (RPC). Distances from the LN center to the closest vessel and adjacent vertebral body were calculated. Using deformable image registration, nodes were mapped to a template CT to provide a visual impression of nodal frequencies and anatomic distribution. Results We identified 72 PET positive paraaortic lymph nodes (37 LPA, 32 AC, 3 RPC). All RPC lymph nodes were in the inferior 1/3 of the paraaortic region. The mean distance from aorta for all lymph nodes was 8.3 mm (range 3 to 17 mm), and from the inferior vena cava was 5.6 mm (range 2 to 10 mm). Of the 72 lymph nodes, 60% were in the inferior third, 36% were in the middle third and 4% were in the upper third of the paraaortic region. 29/30 patients also had FDG-avid pelvic lymph nodes. Conclusions 96% of PET positive nodes were adjacent to the aorta; PET positive nodes to the right of the IVC were rare and were all located distally, within 3 cm of the aortic bifurcation. Our findings suggest that circumferential margins around the vessels do not accurately define the nodal region at risk. Instead, the anatomical extent of the nodal basin should be contoured on each axial image in order to provide optimal coverage of the paraaortic nodal compartment.

Contouring Guidelines for the Axillary Lymph Nodes for the Delivery of Radiation Therapy in Breast Cancer: Evaluation of the RTOG Breast Cancer Atlas

“…The authors found 12 of the 122 nodes were not fully covered by the CTV as defined by the RTOG guidelines (19). Recommendations for increased accuracy of paraaortic and inguinal nodal CTV contouring for conformal RT planning in patients with gynecological malignancies have been proposed by multiple studies (20,21,22).…”

Mapping patterns of nodal metastases in esophageal carcinoma: rethinking the clinical target volume for supraclavicular nodal irradiation

“…The anatomic diagrammatic sketch of the SCV nodes region is shown in Figure 1. The locations of the involved SCV nodes for all patients were then transferred onto a template CT image (registered by hand drawings from the diagnostic CT scan onto the template CT scan) according to methods previously described (19)(20)(21)(22). The volumetric center of each LN was identified and used for subsequent characterization of location.…”

Prophylactic Extended-Field Irradiation in Patients With Cervical Cancer: A Literature Review

“…In the study of Keenan et al ( 67 ), all PALNs were inferior to the left renal vein. Takiar et al ( 68 ) reported that 96% of PALNs were in the inferior and middle third of the PALN region. In the retrospective study by Lee et al ( 33 ), 96 patients received prophylactic sub-renal vein radiotherapy.…”

“…Most PALNs are located in the LLPA and AC regions. Only 4–6% of PALNs are located in the PRC region ( 67 , 68 , 70 ). As LNs in the PRC region are rare and the mean distance from the inferior vena cava to LNs in the PRC region is small, it is reasonable that the node CTV expansion from vessels can be small in the PRC region.…”

“…In addition, PRC LNs are rare above L2 or L3. Takiar et al ( 68 ) reported that all PRC LNs were limited to the inferior third of the para-aortic region (below L3). Keenan et al ( 67 ) found that no PRC lymph node was located above L2 and recommended excluding the RPC region above the L1–L2 interspace.…”