Comparison of positron emission tomography-computed tomography and computed tomography in detecting locally advanced head and neck squamous cell carcinoma

Patients with head and neck tumors raise many diagnostic and therapeutic challenges. The conventional imaging modalities such as CT lack the differentiation between residual and post-radiotherapy changes. The present study aims to assess the diagnostic accuracy of PET-CT scan and to compare it with conventional imaging (CT scan), in detecting persistent locally advanced head and neck cancers. Ten patients (Age>18 years) with histopathologically proven and locally advanced head and neck malignancy, planned for primary Chemo-Radiotherapy with curative intent, were prospectively enrolled in the study. All patients underwent baseline CT and PET-CT scan. CT and PET-CT scans were repeated at 10-12 weeks post-therapy. RECIST/PERCIST criteria were applied for response evaluation of CT and PET/CT respectively. The scans were compared at baseline as well as post-therapy. Concordance-Discordance was evaluated by estimating kappa values in SPSS v22 software. p<0.05 was considered significant. Ten patients (N=10, Male) with locally advanced head and neck cancer were included in the study. Mean age of the patients was 56.5±10.04 years. These 10 patients comprised of 3 patients of base of tongue cancer, 2 of tonsil cancer, 2 of supraglottic laryngeal cancer and 1 each of pyriform sinus, uvula and vallecula cancer. On baseline CT scan, 4 out of 10 patients were negative. In 1 patient, only primary lesion was detected, in 1 patient only nodal lesion was detected while in 4 patients both primary as well as nodal lesions were detected on CT. In comparison, PET/ CT detected primary as well as nodal lesions in 9 patients and in 1 patient only primary lesion was detected. In 4 patients negative on CT, PET/CT was able detect primary as well as nodal lesions in 3 patients and primary lesion in 1 patient. On post-therapy CT scans, 9 patients had partial response and 1 had stable disease. While, 6 patients had complete metabolic response on PET/CT and 3 had partial response. In 1 patient, PET/CT showed progressive disease which had partial response on CT. The kappa value between CT and PET/CT was 0.048 (p=0.62) and 0.096 (p=0.107) at baseline and post-therapy, respectively, indicating discordance between the two modalities. Our results show that PET/CT had higher efficacy in detecting head and neck lesions for primary staging as well as in response evaluation post-therapy. However, study with larger sample size is warranted to establish the findings. (author)