Context: Evaluation of recurrence of disease in the neck in cases of squamous cell carcinoma of upper aerodigestive tract is confounded by the changes rendered by prior surgery, radiation or both. While PET/CT has been described as more accurate than anatomical imaging modalities (CECT/MRI/USG) in western literature, it needs to be re-evaluated in a setting where there is high prevalence of tuberculosis and other chronic granulomatous infection.
Aims: To compare the specificity and sensitivity of PET/CT scan with that of USG and CECT Neck in assessing suspected disease recurrence in cases of squamous cell carcinoma of upper aerodigestive tract previously treated.
Settings and Design: Single center , prospective , observational study over a two year period Methods and Material: Cases of squamous cell carcinoma of upper aerodigestive tract who were on follow-up after finishing their primary therapy and in whom recurrence of the disease is suspected based on clinical examination were enrolled in the study. All cases then underwent analysis of the neck by 18F FDG PET/CT, USG and CECT scan. The histopathology confirmation was obtained by biopsy or FNAC. Sensitivity and specificity of each modality was calculated and compared.
Statistical analysis used: chi square test
Results: A total of 63 patients with mean age 59.87 ( range 39 -82 years) were enrolled in the study. Sensitivity for USG, CT and PET was 66.67 % , 66.67% and 93.55% respectively while specificity was 55.56 % , 48.15 % and 75 % respectively. The positive predictive value(PPV) for USG , CT and PET-CT was 66.67% , 63.16 % and 78.38 % while negative predictive value was55.56% , 52% and 92.31% respectively Conclusions: FDG-PET is more sensitive than conventional imaging modalities in the detection of recurrent cancer in neck. In our scenario, FDG-PET-CT suffers in terms of specificity and positive predictive value for recurrent tumor because it is very sensitive to both tumor and inflammation. With high prevalence of tuberculosis and other chronic granulomatous infections, FDG-PET-CT results in high number of false positive cases. Nevertheless, it remains more specific than conventional modalities. On other hand, a negative FDG-PET-CT scan reliably excludes disease and may obviate unnecessary diagnostic and surgical procedures that ensue from indeterminate clinical or imaging findings in patients who have been previously treated for squamous cell carcinoma of the head and neck.