Impact of post-therapy positron emission tomography on prognostic stratification and surveillance after chemoradiotherapy for cervical cancer

Background: A study was undertaken to investigate the detection of relapse and survival outcomes in patients with cervical cancer treated with curative intent chemoradiotherapy, and evaluated with a post-therapy ¹⁸F- fluorodeoxyglucose positron emission tomography (FDG-PET) scan. Methods: Between January 2002 and June 2007, 105 consecutive patients were prospectively enrolled into a registry study designed to assess outcomes of chemoradiotherapy. A FDG-PET scan was performed between 3 and 12 months (median, 4.9 months) post-treatment at clinician discretion. Tumor response was graded as complete metabolic response, partial metabolic response, or progressive metabolic disease. Results: Median follow-up was 36 months. At post-therapy FDG-PET, 73 (70%) patients had complete metabolic response, 10 (9%) had partial metabolic response, and 22 (21%) had progressive metabolic disease. Overall survival at 3 years was 77% in all patients, and 95% for those with complete metabolic response. On multivariate analysis, complete metabolic response (P <.0001) and pretreatment tumor volume (P =.041) were strong predictors for overall survival. The number of involved lymph nodes (P <.005) and International Federation of Gynecology and Obstetrics stage (P =.04) were predictive of relapse-free survival. In total, 18 patients relapsed at a single site, and 13 underwent salvage, with a 3-year survival of 67%. Patients with complete metabolic response had a distant failure rate 36-fold less than those with partial metabolic response (P <.0001). After complete metabolic response, only 1 patient (1.6%) relapsed without symptoms and was detected through physical examination. Conclusions: The presence of a complete metabolic response at post-therapy FDG-PET is a powerful predictor for survival after chemoradiation. The very low rate of recurrence in patients with a complete metabolic response justifies a conservative follow-up approach for these patients, because relapse is usually symptomatic and not detected by routine clinical review.