The value of post-therapy F-18 FDG PET/CT surveillance scans in the detection of recurrent nasopharyngeal carcinoma

Objectives The role and the frequency of post-therapy surveillance F-18 FDG PET/CT for detecting nasopharyngeal carcinoma (NPC) recurrence are undefined. We analyzed the impact of surveillance scans on outcome at different intervals.

Methods This is a retrospective review of 103 patients with NPC who were referred for post-treatment F-18 FDG PET/CT at our institution. Participants who had a complete metabolic response (CMR) on the early post-therapy scan (within 3 months of the last chemo-radiotherapy cycle) and a minimum of 12 months clinical follow-up were eligible. Recurrence was established with imaging, clinical and/or histological findings. Follow-up PET/CT scans were assessed at different intervals only if preceding scans were negative. Demographics, imaging and pathologic features were described using student T-test, Chi-Square and Kruskal-Wallis as appropriate.

Results A total of 44 patients (mean age ± SD: 44 ± 13 year-old) fit the entry criteria from July 2002 to October 2009. 66% were men, 80% were Asian, 64% were nondrinker, 34% were current/past smokers, and 82% had undifferentiated type (WHO 3 category) on histology. Eight patients had stage I-II NPC (18%) compared to stages III (41%) and IV (41%). Thirty-one patients were disease-free at the time of analysis (group A) and 13 patients had recurrence on follow-up scans (group B). There was no statistically significant difference between the median SUVmax of the primary lesion on the early post-treatment scans in the group who had recurrent disease vs. the group who did not (4.5 vs. 3.7, P=0.10). The detection rates of recurrence were 16% (4 of 38 scans) after 3-12 months post-therapy, 21% (8 of 28) at 13-24 months, 0% (0 of 12) after 25-36 months and 11% (1 of 9) after 37 months.

Conclusions NPC patients who achieved a CMR on the immediate post-treatment F-18 FDG PET/CT seem to benefit from regular surveillance scans up to 24 months. Delayed surveillance scans (>24 months) may not be necessary in patients who already had negative post-treatment scans, thus avoiding additional healthcare costs and radiation.