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					Update on 18F-Fluorodeoxyglucose/Positron Emission
 Tomography and Positron Emission Tomography/
  Computed Tomography Imaging of Squamous
              Head and Neck Cancers


        Semin Nucl Med 35:214-219, 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
• 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??
    Initial staging of squamous head
    and neck cancers with FDG-PET
• Schöder and Yeung                      sensitivity Specificity
  (nodal metastases,                     (%)         (%)
    pretherapy staging??)      FDG-PET 87~90         80~93
•   102 patients with buccal   CT/MRI    61~97       21~100
    mucosa squamous cell
    cancer
•   Dammann and coworkers,               sensitivity specificity
    64 p’t: FDG-PET, CT,                 (%)         (%)
    and MRI                    MRI       93          95
     →in the initial staging
                               FDG-PET   85          98
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 ??
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              sensitivity specificity
    (all FDG-PET studies for          (%)         (%)
    detection of residual and
    recurrent head and neck     PET   86          73
    tumors after radiation
    and/or chemoradiation
    published between 1994      MRI/CT 56         59
    and early 2003)
•   3 to 4 months after
    radiation
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

				
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posted:12/23/2011
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