External Validation of Therapy Response Interpretation Criteria (Hopkins Criteria) with inter-reader reliability, accuracy and Progression free survival outcomes.

Objectives Reliable assessment of PET/CT post-therapy involves reproducible and systematic reporting. A recently introduced response criteria (Hopkins Criteria) has demonstrated promising results in the assessment of head and neck cancer (1). In this study our aim is to re-validate the Hopkins interpretation system, using an external head and neck cancer patients, to assess therapy response and progression free survival in head and neck squamous cell cancer patients (HNSCC).

Methods The study included 69 biopsy proven HNSCC patients who underwent post-therapy PET/CT between 5-24 weeks after completion of therapy. PET/CT images were interpreted by one nuclear medicine physician and one nuclear radiologist independently. The studies scored according to Hopkins Criteria for overall, right neck, left neck, and primary tumor site assessment. Scores 1, 2, 3 were considered as negative and scores 4 and 5 were considered as positive for tumor. Inter-reader variability was assessed using percent agreement and Kappa statistics. Progression-free survival (PFS) was analyzed by Kaplan-Meier plots.

Results Of the 69 patients in the study, 59 (85.5%) were male, 10 (14.5%) were female. Mean age was 62.8 years. There was 91.3%, 97.6%, 97.6%, 91.3% agreement between the readers for overall, right neck, left neck, and primary tumor site response scores, respectively. The corresponding k coefficients were, 0.57, 0.84, 0.78, 0.65 for overall, right neck, left neck, and primary tumor site, respectively. Cox multivariate regression analysis showed positive primary tumor site scores and overall scores were associated with a higher risk of progression (p<0.05).

Conclusions External validation of Hopkins Criteria shows excellent inter-reader agreement and prediction of PFS in HNSCC patients.