Para-aortic lymph nodal staging and evaluation of treatment outcome by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in advanced cancer cervix

Purpose: Computer tomography and ultrasonography are commonly used for baseline evaluation for carcinoma of uterine cervix. Addition of functional imaging using FDG PET CT may aid in diagnosing the patients with occult para-aortic nodes and / or distant metastasis. This technique need to be validated rigorously before routine clinical use. We attempted to evaluate & validate the use of FDG PET-CT for carcinoma cervix as baseline imaging. Material and methods: Patients diagnosed with carcinoma cervix stage IIB & IIIB were included for this study and underwent pretreatment FDG PET-CT done as per the protocol approved by an institutional ethics committee. All the patients were treated with curative intent radiotherapy (External / extended field radiation and brachytherapy). Concurrent chemotherapy was used for patients with good renal function. Patients with conventional imaging suggestive of para-aortic nodal disease but negative on PET-CT or patients with conventional imaging and PET- CT both suggestive of para-aortic nodes were treated with extended field radiation therapy encompassing the para-aortic region and pelvic nodes. The patients with conventional imaging negative for para-aortic nodal disease but positive on PET imaging were treated with pelvic radiation therapy only. Results: Between September 2005 to November 2008, 96 patients were enrolled in this protocol. The median age of the cohort was 49 years (Range 32-66 years). Squamous carcinoma was the commonest histology (92%). On clinical examination, 60% of patients had FIGO stage IIB, while remaining had stage IIIB. Thirteen patients (14%) were upstaged after PET CT (having Para-aortic nodes), while 5 patients were down staged of having only pelvic nodes (conventional imaging showed para-aortic nodes). The median dose of external RT was 50 Gy. Eighty eight (92%) received concurrent chemotherapy (Median number of cycles 5). At median follow of surviving patients of 74 months (Range 5-102 months), 5 year disease free survival (DFS) is 59% and 5 year overall survival (OS) is 63%. Disease free survival and OS was significantly inferior for patients having para-aortic nodes on PET CT as compared to patients without para-aortic nodes, while there was no difference in OS or DFS for patients having para-aortic nodes on conventional imaging as compared to patients without para-aortic nodes. Conclusion: PET-CT as a baseline investigation for carcinoma of uterine cervix is feasible. Detection of para-aortic nodes on PET-CT signifies poorer outcomes as compared to detection of the same by conventional imaging. (author)