Utility of PET in unknown primary with cervical metastasis: A retrospective study

Background: FDG-PET is recommended as an investigation in unknown primary tumors, but its definitive role and cost effectiveness are yet to be established.
Aims: dditional value of FDG-PET over conventional imaging in unknown primary tumors with cervical metastasis.
Setting and Design: Retrospective study in a tertiary level oncology centre.
Materials and Methods: A total of 112 patients were divided into three groups; 53 with conventional modalities (either computed tomography or magnetic resonance imaging) (group I), 59 with FDG-PET (group II), and group III (subgroup of group II) with both (40 patients).
Statistical Analysis: Sensitivity and specificity of both conventional modality and PET were calculated. Association between neck nodes and distant metastasis was analysed using multivariate logistic regression analysis.
Results: Sensitivity and specificity for conventional modalities was 92.3% and 50% and sensitivity and specificity of FDG-PET was 92.8% and 71.4%, respectively. FDG-PET detected metastasis in 52.54% of patients. Multivariate logistic regression analysis showed statistically significant association between distant metastasis and multiplicity of nodes (N2b, N2c) (P = 0.007). Among all patients with low neck nodes in group II, FDG-PET detected primaries in 12 patients, 9 of which were infraclavicular (75%). FDG-PET added information to conventional imaging in 32.5% of patients and influenced an overall change in management in 38.9% of patients.
Conclusions: FDG-PET is a valuable tool influencing change of management in unknown primary with cervical metastasis. It is recommended especially in the presence of low or multiple neck nodes in view of high incidence of infraclavicular primary and distant metastasis, respectively.