Anatomic distribution of [(18)F] fluorodeoxyglucose-avid lymph nodes in patients with cervical cancer

Current information about the anatomic distribution of lymph node (LN) metastases from cervical cancer is not precise enough for optimal treatment planning for highly conformal radiation therapy. To accurately define the anatomic distribution of these LN metastases, we mapped [(18)F] fluorodeoxyglucose positron emission tomography (FDG PET)-positive LNs from 50 women with cervical cancer.

Records of patients with cervical cancer treated from 2006 to 2010 who had pretreatment PET/computed tomography (CT) scans available were retrospectively reviewed. Forty-one consecutive patients (group 1) with FDG-avid LNs were identified; because there were few positive paraortic LNs in group 1, 9 additional patients (group 2) with positive paraortic LNs were added. Involved LNs were contoured on individual PET/CT images, mapped to a template CT scan by deformable image registration, and edited as necessary by a diagnostic radiologist and radiation oncologists to most accurately represent the location on the original PET/CT scan.

We identified 190 FDG-avid LNs, 122 in group 1 and 68 in group 2. The highest concentrations of FDG-avid nodes were in the external iliac, common iliac, and paraortic regions. The anatomic distribution of the 122 positive LNs in group 1 was as follows: external iliac, 78 (63.9%); common iliac, 21 (17.2%); paraortic, 9 (7.4%); internal iliac, 8 (6.6%); presacral, 2 (1.6%); perirectal, 2 (1.6%); and medial inguinal, 2 (1.6%). Twelve pelvic LNs were not fully covered when the clinical target volume was defined according to Radiation Therapy Oncology Group guidelines for intensity modulated radiation therapy for cervical cancer.

Our findings clarify nodal volumes at risk and can be used to improve target definition in conformal radiation therapy for cervical cancer. Our findings suggest several areas that may not be adequately covered by contours described in available atlases.