Evaluation of the role of 18FDG-PET/CT in radiotherapy target definition in patients with head and neck cancer

Acta Oncol. 2008;47(7):1229-36. doi: 10.1080/02841860802256483.


Background and purpose: As techniques for radiotherapy delivery have developed, increasingly accurate localisation of disease is demanded. Functional imaging, particularly PET and its fusion with anatomical modalities, such as PET/CT, promises to improve detection and characterisation of disease. This study evaluated the impact of (18)FDG-PET/CT on radiotherapy target volume definition in head and neck cancer (HNC).

Materials and methods: The PET/CT scans of patients with HNC were used in a radiotherapy planning (RTP) study. The gross tumour volume (GTV), clinical target volume (CTV) and planning target volume (PTV) were defined conventionally and compared to those defined using the PET/CT. Data were reported as the median value with 95% confidence intervals.

Results: Eighteen patients were consented, 9 had known primary tumour site, 9 presented as unknown primary. In nine cases where the primary site was known, the combined primary and nodal GTV (GTVp+n) increased by a median of 6.1cm(3) (2.6, 12.2) or 78% (18, 313), p=0.008 with CTV increasing by a median of 10.1cm(3) (1.3, 30.6) or 4% (0, 13) p=0.012. In 9 cases of unknown primary the GTVp+n increased by a median 6.3 cm(3) (0.2, 15.7) or 61% (4, 210), p=0.012, with CTV increasing by a median 155.4 cm(3) (2.7, 281.7) or 95% (1, 137), p=0.008.

Conclusion: (18)FDG-PET revealed disease lying outside the conventional target volume, either extending a known area or highlighting a previously unknown area of disease, including the primary tumour in 5 cases. We recommend PET/CT in the RTP of all cases of unknown primary. In patients with a known primary, although the change in volume was statistically significant the clinical impact is less clear. (18)FDG-PET can also show areas within the conventional target volume that are hypermetabolic which may be possible biological target volumes for dose escalation studies in the future.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Aged
  • Fluorodeoxyglucose F18
  • Head and Neck Neoplasms / diagnosis*
  • Head and Neck Neoplasms / pathology
  • Head and Neck Neoplasms / radiotherapy*
  • Humans
  • Lymphatic Metastasis
  • Male
  • Middle Aged
  • Neoplasm Staging
  • Neoplasms, Unknown Primary / radiotherapy
  • Positron-Emission Tomography*
  • Tomography, X-Ray Computed*
  • Tumor Burden


  • Fluorodeoxyglucose F18