Purpose: To evaluate if any linear relationship exists between CA–125 levels and degree of disease burden in suspected recurrent ovarian carcinoma cases on PET/CT and to establish a possible CA–125 cut-off value which could predict whether the active disease predominantly involves lymph nodal stations or intra-abdominal soft tissue sites.
Methods: This retrospective study involved 42 patients (35-74 years) with suspected disease recurrence based on raised CA–125 levels referred for PET/CT scan. Patients were classified into three groups based on the range of CA–125 levels. Number of lesions per patient was counted. Data analysis was done using appropriate statistical tests. Results: PET/CT detected a total of 57 lesions in Group A (n=18), 68 in Group B (n=14) and 65 lesions in Group C (n=10) respectively. No significant statistical difference was found in the total number of lesions detected in all the three groups. No significant statistical difference was seen when comparing total number of lesions detected on PET/CT in groups with marked difference in CA–125 levels. When the number of lesions detected on PET/CT in each patient was correlated, no correlation (r = 0.342) between the CA–125 levels and disease burden was observed. A cut-off CA–125 value of 350 U/ml was established to be significant (p-value <0.001) in suggesting whether the active disease predominantly involves lymph node or intra–abdominal soft tissue sites. Conclusion: There exists no relationship between CA–125 levels and degree of disease burden detected on PET/CT suggesting that higher degree of disease burden may be found in low levels of raised CA–125 levels and vice versa. A cut-off of 350 U/ml of CA–125 may be useful to predict the predominant disease distribution pattern i.e. lymph nodal stations versus soft tissue deposits in these patients.
Key words: CA -125, 18F-FDG PET/CT, Ovarion carcinoma.