Update on 18 F-Fluorodeoxyglucose/Positron Emission Tomography and Positron Emission Tomography/ Computed Tomography Imaging of Squamous Head and Neck Cancers Semin Nucl Med 35: , 2005 Intern 呂學儒

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

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

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

Initial staging of squamous head and neck cancers with FDG-PET Sch ö der 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 sensitivity （％） Specificity （％） FDG-PET87~9080~93 CT/MRI61~9721~100 sensitivity （％） specificity （％） MRI9395 FDG-PET8598

Initial staging of squamous head and neck cancers with FDG-PET ： PET/CT vs. 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 ??

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%

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

Radiotherapy planning PET-CT with FDG （ preradiotherapy staging of 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

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

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

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 ％

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 sensitivity （％） specificity （％） PET8673 MRI/CT5659

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%

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

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