Objective: To determine disease free survival (DFS) and progression free survival (PFS) and their predictors in patients with nasopharyngeal cancer (NPC) having achieved complete (CMR) and partial metabolic response (PMR) on post-chemoradiation (CRT) 18FDG PET/CT.
Materials and methods: Retro-prospective study conducted at PET/CT Section of JCIA accredited healthcare facility of Pakistan. Total 73 patients of NPC patients who had baseline and post-CRT 18FDG PET/CT were included and prospectively followed till predefined study end points of recurrence or disease progression or death from April-2016 till January 2024. Based on CMR on post-CRT 18FDG PET/CT, 45 patients labelled as responders while 28 with PMR as non-responders. Using logistic regression and ROC analysis, the predictors of recurrence and disease progression were analyzed in both groups. Kaplan Meier's survival plots were analyzed to measure DFS in responders and PFS in non-responders respectively.
Results: Body mass index (BMI), SUVmax and Stage-IV disease were found significantly higher in non-responder group. DFS in responders was significantly higher than PFS in non-responder (60.157 month ± 8.047 Vs 8.145 months ± 1.851). DFS was seen in 84% of responder group with 16% recurrence (7/45). Baseline SUVmax >14.2 and primary tumor size (PTS) > 41 mm were found significant predictors of recurrence in responder group. In the non-responder group, the PFS was found in 54% patients while 46% patients (n=13/28; 2 expired) had disease progression. No significant predictor was found for PFS in the non-responder group. In DFS the mean survival was significantly higher in patients with SUVmax ≤14.2 versus >14.2 (Mean Survival 67.390 vs. 38.283 months; Logrank 9.899; p=0.0017*). However, near significant difference was observed in non-responder group in their PFS at SUVmax ≤11.9 vs. >11.9 (Mean Survival 10.00 vs. 7.05 months; Logrank=3.096; p=0.0798).
Conclusion: 18FDG PET/CT scan precisely stratifies the treated NPC patients into responders having longer DFS and non-responders having shorter PFS. Higher BMI, SUVmax of primary tumor and metastatic disease were found to have significant association in non-responders. In responders, PTS >41 mm and its SUVmax >14.2 were found significant predictors of recurrence. In non-responders, SUVmax >11.9 was found to have near significant association with disease progression.
Keywords: PET/CT; nasopharynx cancer; progression free survival; recurrence- disease free survival-predictor.