The role of PET/CT with fluorine-18-deoxyglucose in the detection of relapsed serous ovarian cancer in patients with normal serum CA125 levels.

Objectives: To assess the role of the positron emission tomography with fluorine-18-deoxyglucose (PET/CT) in the detection of recurrent serous ovarian cancer in patients with normal serum CA125 level.

Material and methods: Thirty-one patients with suspected recurrent serous ovarian cancer with normal (< 35 IU/mL) serum CA125 level and no prior recurrence underwent PET/CT imaging. The results of the PET/CT were analyzed considering clinical data of the patients, histological diagnosis and 6 months follow-up.

Results: The patients were referred to the PET/CT due to suspected relapse in imaging tests (CT - 11 cases, US - 3 cases, MRI - 2 cases; n = 16; 51.6%), clinical examination (n = 4; 12.9%) and clinical symptoms (n = 11; 35.5%). The recurrent serous ovarian cancer was present in 16 patients (51.6%). In 9 these cases (56.3%) the recurrences were diagnosed in patients aged 51-70 years. In 15 cases (93.8%) the recurrences were diagnosed within 24 months after treatment. There were 15 true positive (48.4%), 12 true negative (38.7%), 3 false positive (9.7%) and 1 false negative (3.2%) PET/CT results. Sensitivity, specificity, positive and negative predictive value of the PET/CT were calculated as 93.8% (95% CI, 86.1-97.4%), 80.0% (95% CI, 69.7-88.9%), 83.3% (95% CI, 74.3-90.4%) and 92.3% (95% CI, 84.2-98.3%), respectively.

Conclusions: In patients with a diagnosis of complete remission after treatment for serous ovarian cancer, even a multifocal recurrence may occur during follow up despite normal serum CA125 levels. Our results showed a usefulness of the PET/CT in detecting and differentiating malignant from benign lesions in patients with normal serum CA125 levels but inconclusive results in other imaging tests. We observed false results of the PET/CT for lesions in parotid gland, mesorectal adipose tissue and mediastinal lymph nodes.