# 18F-NaF PET/CT changed T category in 9.4% of 265 nasopharyngeal carcinoma patients in retrospective study

- Published: 2026-11-13 07:18 UTC
- Section: Life & Health › Medicine
- Tags: nasopharyngeal carcinoma, 18F-sodium fluoride PET/CT, AJCC/UICC Version 9, T-category reclassification, M-category reclassification, skull-base bone involvement, skeletal metastases, radiotherapy target volumes, propensity score matching, retrospective cohort study
- URL: https://realtech.media/news/rt-a094381724b0725fc5f12f8f_18f_naf_pet/

**In a retrospective single-center cohort of 265 patients, adding 18F-NaF PET/CT changed T category in 25 and M category in 13; target contours changed in selected cases.**

![18F-NaF PET/CT changed T category in 9.4% of 265 nasopharyngeal carcinoma patients in retrospective study](https://realtech.media/media/2026/11/e4ffbd55b2e7c0da.jpg)
*Partynia, Wikimedia Commons, CC BY-SA 4.0*

A retrospective single-center cohort study examined 265 patients with newly diagnosed nasopharyngeal carcinoma (NPC) who underwent pretreatment conventional imaging and 18F-sodium fluoride (18F-NaF) PET/CT. The authors assessed how the added scan affects staging and radiotherapy target volumes. The paper in BMC Medical Imaging (2026) is available via doi.org; staging followed AJCC/UICC Version 9 criteria applied retrospectively [1].

## Staging changes after adding 18F-NaF PET/CT

Accurate assessment of skull-base bone involvement and skeletal metastases is essential for NPC staging and radiotherapy planning [1]. After 18F-NaF PET/CT was added, T category changed in 25 of 265 patients (9.4%; 95% CI, 6.5%-13.6%) [1]. M category changed in 13 of 265 patients (4.9%; 95% CI, 2.9%-8.2%) [1].

Four patients had established M1 disease whose M category stayed the same. In three of them, 18F-NaF revealed additional avid skeletal findings [1].

## Effect on radiotherapy target volumes

Paired gross tumor volume (GTV), clinical target volume (CTV) and planning target volume (PTV) data were available for 11 of the 25 patients with T reclassification. The other 14 were excluded because technical limitations prevented reliable image registration between CT and 18F-NaF PET/CT [1]. As a comparison, 30 of 183 eligible patients with unchanged T category were chosen by a computer-generated random-number sequence [1].

In the NaF-positive/MRI-negative cohort, median paired volume increases were 0.96 cm3 for GTVnx, 4.50 cm3 for CTV and 6.45 cm3 for PTV. In the NaF-positive/MRI-positive cohort they were 3.80, 1.75 and 0.05 cm3, respectively [1].

An exploratory 1:1 propensity score-matched analysis used age, sex and AJCC/UICC Version 9 stage. In 11 matched pairs, relative CTV and PTV changes were numerically larger in the T-changed cohort. Residual covariate imbalance persisted after matching, which limits interpretation [1].

## Limitations

The authors state that the findings reflect imaging-based stage reclassification. The effect of 18F-NaF PET/CT on staging accuracy requires validation against an independent reference standard. Given the retrospective single-center design, the small contouring cohort and the residual imbalance, the authors call for prospective validation before routine clinical adoption [1].

## Sources

1. [doi.org](https://doi.org/10.1186/s12880-026-03017-4)
2. [bioengineer.org](https://bioengineer.org/adding-sodium-fluoride-pet-ct-alters-staging-and-radiotherapy-volumes-in-nasopharyngeal-carcinoma)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-a094381724b0725fc5f12f8f_18f_naf_pet/