Intern 呂學儒

1. Update on 18F-Fluorodeoxyglucose/Positron EmissionTomography and Positron Emission Tomography/Computed Tomography Imaging of SquamousHead and Neck CancersSemin Nucl Med 35:214-219, 2005 Intern 呂學儒

2. Introduction • PET/CT ：used widely；not adequately evaluated for head and neck cancer • Its accuracy in initial staging：better than CT；similar to MRI • Appropriate if sentinel node mapping is performed in patients with PET studies showing no nodal disease • Identifying malignant normal size nodes, extent of viable tumor, and distant disease

3. Initial staging of squamous head and neck cancers with FDG-PET • Radiotherapy planning • Carcinoma of unknown primary of squamous cell origin • Evaluation of response to radiation and/or chemoradiation therapy

4. Initial staging of squamous head and neck cancers with FDG-PET • Cervical lymph node • surgery (type of neck dissection, unilateral versus bilateral) and radiotherapy field • 18F-fluorodeoxyglucose (FDG)-PET：recurrent head and neck cancer vs. initial staging of them??

5. Initial staging of squamous head and neck cancers with FDG-PET • Schöder and Yeung （nodal metastases, pretherapy staging??） • 102 patients with buccal mucosa squamous cell cancer • Dammann and coworkers, 64 p’t： FDG-PET, CT, and MRI →in the initial staging

6. Initial staging of squamous head and neck cancers with FDG-PET • Anatomic information：PET/CT vs. PET • Syed and coworkers（ 24 patients ）：PET/CT for head and neck cancer before their treatment → PET/CT downstaged the disease and changed the management in 17% of patients, by correctly assigning areas of increased uptake to fat or muscle tissue • PET/CT, MRI, and multi-slice CT ??

7. Initial staging of squamous head and neck cancers with FDG-PET • N0 neck vs. 25% to 30% have metastatic neck nodes at surgery • 48 patients, in which a sentinel node biopsy with immunohistochemistry was used as gold standard → The detection rate of PET： 0~ 30% →40% of cervical nodal metastases are less than 1 cm in size and PET detection rate for nodes less than 1 cm is reported at 71%

8. Initial staging of squamous head and neck cancers with FDG-PET • FDG-PET vs. conventional imaging in pretherapy staging ：detect contralateral disease and distant synchronous and/or metastatic disease in the chest and abdomen

9. Radiotherapy planning • PET-CT with FDG（preradiotherapy stagingof head and neck cancer）：sensitivity 96%；specificity 98.5% • Ciernik and coworkers：the coregistration of PET-CT with the planning CT images average deviations x axis = 1.2 ±0.8 mm y axis = 1.5 ± 1.2 mm z axis= 2.1 ±1.1 mm • Paulino and coworkers：error of less than 5 mm

10. Radiotherapy planning • The target volume may be increased because metabolically active tumor can be detected in normal sized nodes • The PET-based GTV is smaller than CT-based GTV in some patients due to partially necrotic

11. Carcinoma of unknown primary of squamous cell origin • Cervical nodal metastases from an unknown primary tumor： 2% • Irradiation（the entire pharyngeal mucosa, larynx, and bilateral neck）：reduces the risk of tumor recurrence vs. significant morbidity, particularly in terms of xerostomia • CT and/or MRI：50% • Endoscopy and directed biopsies：significantly higher if a primary tumor is suggested by radiological exams or physical examination findings • The most common sites：the tonsil/tonsillar fossa and the base of the tongue

12. Carcinoma of unknown primary of squamous cell origin • Rusthoven and coworkers（between 1992 and 2003）：PET was performed after a negative endoscopy and negative CT and/or MRI → the detection rate 27% • Additional local and distant metastases：27% of patients • The relatively high false-positive rate related to variable physiologic uptake of FDG in head and neck structures • sensitivity（18 p’t） CT：PET：PET/CT=25％：25％：36％

13. Evaluation of response to radiation and/or chemoradiation therapy • Klabbers and coworkers（all FDG-PET studies for detection of residual and recurrent head and neck tumors after radiation and/or chemoradiation published between 1994 and early 2003） • 3 to 4 months after radiation

14. Evaluation of response to radiation and/or chemoradiation therapy • Earlier evaluation for many patients treated with chemoradiation, due to salvage surgery, if residual disease is present • Salvage surgery within 6 to 8 weeks after radiation, before postradiation fibrotic changes develop in the neck • Goerres et al studied（26 patients with advanced head and neck cancer after concomitant chemoradiation） and PET findings vs. histopathology in PET positive cases clinical follow-up for 6 months in PET negative cases →the sensitivity 90.95%, specificity 93.3%

15. Evaluation of response to radiation and/or chemoradiation therapy • Nam and coworkers（24 patients）： PET 4 weeks after definitive radiation therapy 2 patients with residual disease and only 1/22 patients with a negative PET scan developed recurrent disease over a median follow-up of 12 months • many as 50% of the recurrences occur more than 15 months after the treatment → early PET can be confidently used as a routine

16. Evaluation of response to radiation and/or chemoradiation therapy • When is the timing of the scan?? • Rogers and coworkers：low sensitivity of 45% for a 1-month posttherapy FDG-PET • Yao and coworkers（ 15 patients ） ：Comparing the 3- to 4-month posttherapy PET data with histology from salvage surgery → sensitivity of 100% and specificity of 82% • In summary, a PET scan performed 2 to 5 months after therapy has a high NPV so that patients can be safely followed without intervention