Tumour and pelvic lymph node metabolic activity on FDG-PET/CT to stratify patients for para-aortic surgical staging in locally advanced cervical cancer.

Purpose: The aim of our study was to comprehensively evaluate the most valuable metabolic parameters of cervical tumours and pelvic lymph nodes (PLN) by FDG-PET/CT to predict para-aortic lymph node (PALN) metastasis and stratify patients for surgical staging.

Methods: The study included patients with locally advanced cervical cancer, negative PALN uptake on preoperative FDG-PET/CT, and para-aortic lymphadenectomy. Two senior nuclear medicine physicians expert in gynaecologic oncology reviewed all PET/CT exams, and extracted tumour SUVmax, MTV, and TLG, as well as PLN. Prognostic parameters of PALN involvement were identified using ROC curves and logistic regression analysis.

Results: One hundred and twenty-five consecutive locally advanced cervical cancer patients were included. The FDG-PET/CT false-negative rate was, respectively, 27.7% (13/47) and 5.1% (4/78) in patients with and without FDG-PET/CT PLN uptake. The AUC of cervical tumour size, SUVmax, MTV, and TLG was, respectively, 0.75 (0.62-0.87), 0.59 (0.44-0.76), 0.75 (0.60-0.90), and 0.71 (0.56-0.86). The AUC of PLN size, SUVmax, SUVmean, PLN SUVmax/Tumour SUVmax ratio, MTV, and TLG was, respectively, 0.57 (0.37-0.78), 0.82 (0.68-0.95), 0.77 (0.61-0.94), 0.85 (0.72-0.98), 0.69 (0.51-0.87), and 0.74 (0.57-0.91). The metabolic parameter showing the best trade-off between sensitivity and specificity to predict PALN involvement was the ratio between PLN and tumour SUVmax.

Conclusion: The risk of PALN metastasis in FDG-PET/CT negative PLN patients is very low, so para-aortic lymphadenectomy does not seem justified. In patients with preoperative PLN uptake on FDG-PET/CT, surgical staging led to treatment modification in more than 25% of cases and should therefore be performed. Patients with more than one positive PLN and high PLN metabolic activity are at high risk of para-aortic extension and recurrence. Further prospective evaluation is required to consider intensified treatment modalities without prior PALN dissection.