PURPOSE: In cancer of the uterine cervix, lymph node metastases are associated with a poor prognosis. Even so, the International Federation of Gynecology and Obstetrics (FIGO) does not take into account diagnostic results of methods such as PET/CT, since these are not readily available everywhere. As undetected lymph node metastases can lead to undertreatment, any difference in the underlying prevalence of false-negative scans between CT and PET/CT may be reflected in treatment outcomes. This study investigated survival outcomes in node-negative patients before and after the introduction of PET/CT.

METHODS: This was a single-institution retrospective analysis of 301 patients with a histopathological diagnosis of cervical cancer. The patients were receiving chemoradiotherapy with curative intent according to the standard protocol of the department for patients without lymph node metastases as assessed by pretreatment CT or PET/CT. Patients were stratified into two groups: PET/CT and non-PET/CT. Patient characteristics and treatment outcomes were acquired from the treatment database.

RESULTS: Significant differences of 23 % (95 % CI 17 - 29 %), 19 % (95 % CI 13 - 25 %) and 12 % (95 % CI 6 - 18 %) in 5-year overall, disease-free and disease-specific survival, respectively, were observed between the two patient groups. The difference remained significant in univariate and multivariate analyses of overall survival (hazard ratio 0.61, 95 % CI 0.42 - 0.89; p = 0.010), including age, FIGO stage, performance status, BMI, and histopathology.

CONCLUSION: Inclusion of PET/CT in the preradiotherapy diagnostic protocol may lead to nodal stage migration not reflected in the FIGO stage. It was found to be a significant covariate, and could lead to selection bias that needs to be taken into account when designing and reporting on clinical trials.