New FDG-PET/CT interpretation criteria (Huaxi criteria) for response assessment in patients with nasal-type extranodal NK/T-cell lymphoma: development and validation.

The Deauville criteria are recommended for PET/CT-based treatment response evaluation in extranodal NK/T-cell lymphoma (ENKTL) but have limited prognostic value. Therefore, we conducted a retrospective study of 340 nasal-type ENKTL patients to develop new criteria (Huaxi criteria) and validate them for assessing therapeutic response and survival outcome. 80% (140/175) of the patients who did not receive any anticancer therapy after the end-of-treatment PET/CT (EOT-PET/CT) and had a progression-free survival > 24 months were randomly selected as subjects for developing Huaxi criteria. On EOT-PET/CT, the SUV of initial and new lesions at each site (including the upper aerodigestive tract [UADT] and nodal and extranodal sites) and liver SUV were measured to calculate the lesion-to-liver ratio (LLR). The 99th percentile upper-reference limits of the LLRs of lesions at each site were used to divide the lesion response into complete metabolic response (CMR) and non-CMR/new tumor. The Huaxi criteria were then established using an LLR-based 3-point scoring system. Interreader agreement was assessed using kappa statistics. Kaplan‒Meier and Cox regression analyses were used to compare survival outcomes. The prognostic ability was assessed using the hazard ratio (HR), which was calculated via univariate Cox regression analysis. The results showed that the LLR thresholds for assessing CMR and non-CMR/new tumor at the UADT and nodal and extranodal sites were 2.0, 1.5 and 1.0, respectively. The Huaxi criteria were employed to score the lesions at each site using the LLR-based 3-point scale, with the highest score denoting the overall response. Scores 1 and 2 represent CMR, and score 3 represents non-CMR. Interreader agreement was substantial for the Huaxi criteria but only moderate-substantial for the Deauville criteria (κ, 0.663‒0.756 vs. 0.454‒0.711). The Huaxi criteria improved the positive predictive value (PPV) for prognosis from 21.9‒41.4% with the Deauville criteria to 53.4‒73.1%. The Huaxi criteria were an independent prognostic factor at EOT and interim (all P < 0.001), with better predictive performance than the Deauville criteria (HR, 5.25‒11.56 vs. 1.59‒3.66, all P < 0.05). In conclusion, the Huaxi criteria are concise, with substantial interreader agreement and a high PPV for prognosis, and can independently predict outcomes in nasal-type ENKTL patients.