Download An Introduction to PET Imaging in Oncology

Janet McLaren
Gillian Lieberman, MD
January 2002
An Introduction to PET
Imaging in Oncology
Janet McLaren, Harvard Medical School Year III
Gillian Lieberman, MD
Janet McLaren
Gillian Lieberman, MD
Basics of PET
• Principle of “Physiologic Imaging:”
– Allows in vivo visualization of structures by their ability to
concentrate specific labeled molecules
– Most commonly used compound: fluorodeoxyglucose (FDG)
• Past use had been limited due to cost of dedicated PET
scanners and the difficulty in obtaining isotopes
• Recent advances have made PET more feasible:
– Modification of dual head gamma camera SPECT systems
– Increase in availability of isotopes
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Janet McLaren
Gillian Lieberman, MD
FDG: The Compound
CH2OH
O
OH
HO
OH
[18F] FDG
• 2-deoxy-2-(18F)fluoro-D-glucose
• 18F: positron-emitting isotope of fluorine
• Metabolically active cells utilize more glucose than other
tissues and therefore uptake more FDG
• FDG is phosphorylated by hexokinase upon entry into the
cell but cannot undergo further glycolytic reactions
• Dephosphorylation of the compound is slow, limiting
transport out of the cell
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Janet McLaren
Gillian Lieberman, MD
FDG: The Isotope
CH2OH
O
OH
HO
OH
[18F] FDG
• 18F: emits positrons as it decays
• Positrons travel until they collide with an electron
• This collision produces two electromagnetic pulses of
511 keV that are detected by the PET detectors
• Signal can be quantified: SUV (standardized uptake value)
(+)
– SUV > 2.5 generally used to indicate “increased uptake”
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Janet McLaren
Gillian Lieberman, MD
Applications
• Oncology
– Diagnosis: benign vs. malignant process
– Staging
– Post-therapy evaluation: response to tx or to identify
recurrence
 PET is approved for imaging of lung, lymphoma, colon
and melanoma cancers
• Assessment of Cardiac Viability
– Used to evaluate myocardial perfusion and viability
• CNS
– Functional analysis
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Janet McLaren
Gillian Lieberman, MD
Oncologic Imaging
• FDG identifies hypermetabolic cells:
– Malignancy
– Infection
– Inflammation
• FDG false (-)s, specific to malignancy:
– Small tumor size
– Relatively low tumor metabolic activity (i.e. welldifferentiated tumors, including bronchoalveolar)
– Hyperglycemia: dilutes uptake of FDG
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Janet McLaren
Gillian Lieberman, MD
PET and the SPN
•
•
•
•
130,000 new Solitary Pulmonary Nodules (SPN)/year
40% of non-calcified SPN seen on CXR are benign
A significant number of these remain indeterminate after CT
Transthoracic FNA: high false (-) rate, diagnosis obtained in
less than 50% of patients
• PET:
– Sensitivity and specificity of 95% and 81% for detecting malignancy
 PET Imaging is for patients who will have treatment
planned according to PET results, i.e. thoracotomy or f/u
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Janet McLaren
Gillian Lieberman, MD
PET and the DDx of a SPN
DDx:
• Benign Tumor
• Round pneumonia
• Malignant Tumor
• A/V malformation
SUV
>2.5
Narrowed DDx:
• Cancer
• Cancer
• Metastatic Tumor • Rheumatoid Nodule
• Cancer
• Granuloma
• Granuloma/Rheumatoid
From BrighamRad Teaching Cases:
http://brighamrad.harvard.edu/Cases/bwh/hcache/147/full.html
From Metro Region PET Center: SPN Case Study
http://www.woodburnnm.com/study_spn.htm
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Janet McLaren
Gillian Lieberman, MD
• Oncologic Applications
of PET:
– Diagnosis
– Staging
– Follow-up
• Post-surgical
• Response to chemo/RT
 Utility of PET in each of
these areas varies among the
different types of cancers
From GE Medical Systems
http://www.gemedicalsystems.com/index.html
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Janet McLaren
Gillian Lieberman, MD
Patient #1: SPN
Nodule
• 84 year-old man with a
solitary pulmonary nodule
found on routine CXR.
• Nodule was followed by
CT for 2 years and found
to be stable.
• A few years later, PET
became available for SPN
evaluation.
Courtesy of Dr. Vincent Chan, BIDMC
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Janet McLaren
Gillian Lieberman, MD
Patient
#1: SPN
• A PET Scan
showed the
nodule to have
increased activity
• The nodule was
biopsied and
found to be an
adenocarcinoma
Courtesy of Dr. Vincent Chan, BIDMC
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Janet McLaren
Gillian Lieberman, MD
Patient #1: SPN  Lung CA
• Diagnosis
– PET can diagnose lesions deemed indeterminate by CT
and thus is invaluable in the work-up of a SPN
• Staging
– In patients with known NSCLC, PET provides significant
staging and prognostic information
• CT vs PET in assessment of nodal status
• 1999 Study: PET changed tx in 37% of cases
 Appropriate use of PET in the work-up of a
SPN will prevent unnecessary operations and may
prove to be cost effective
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Janet McLaren
Gillian Lieberman, MD
Patient #2: Breast Cancer
• 58 year-old woman
presented with a breast
mass after many years
without clinical care
• This mammogram was
obtained
• Diagnosed with
inflammatory breast cancer
• The patient was referred to
Nuclear Medicine for
staging
From Southern Illinois University School of Medicine
(www.siumed.edu/biomed/098-005.htm)
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Janet McLaren
Gillian Lieberman, MD
Patient #2: Breast Cancer
• PET Scan findings:
– Primary Left Breast
Mass
– Mets to the Left Axilla
LNs
– Met to the Liver
movie
Courtesy of Dr. Vincent Chan, BIDMC
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Janet McLaren
Gillian Lieberman, MD
Patient #2: Breast Cancer
• Diagnosis
– Most breast cancer is detected by mammo or PE
– PET can be used for equivocal lesions to avoid biopsy, or
in patients with prior surgery or implants
• Staging
– Sentinel Node Biopsy remains the preferred method of
detecting axillary node metastsis
– PET plays a useful role in identifying distant metastases
• Shown superior to bone scan in detecting osteolytic lesions
• Follow-Up
– Limited data show PET can be used to monitor response
to chemo as early as 8 days into treatment
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Janet McLaren
Gillian Lieberman, MD
Patient #3: Melanoma
• 35 year-old man
presented with a lesion
on his back
• On excision, the lesion
was found to be
invasive melanoma
• Patient was referred to
Nuclear Medicine for
staging
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient
#3:
Melanoma
PET Scan showed high
activity in the left axilla
and in a small area of
the upper mediastinum
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient
#3:
Melanoma
• The increased
activity in the upper
mediastinum was
thought to be artifact
• The patient was
treated with surgical
excision of the left
axillary lymph nodes
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Normal brain uptake
Patient #3:
Melanoma
Healing
tissue
• 6 months later the patient returned for
follow-up
• The follow-up PET Scan revealed
growth of the upper mediastinal mass
• The mass was excised and confirmed to
be metastatic melanoma
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #3: Melanoma
• Staging
– Sentinel Node Biopsy remains the preferred method of
determining regional lymphatic spread
– PET is preferred and superior to CT and MRI for
identifying distant metastatic lesions
– Data: sensitivity and specificity of 94% and 83% for PET
vs. 55% and 84% for CT
 PET is very useful in identification and staging of
cancers that metastasize widely or in an unpredictable
manner
(e.g. melanoma, lymphoma, head and neck cancer
)
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Janet McLaren
Gillian Lieberman, MD
Patient #4
• 78 year old female
• S/p colectomy and
partial hepatectomy for
metastatic colon CA
seven years prior
• Rising CEA (10.0)
Courtesy of Dr. Vincent Chan, BIDMC
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Janet McLaren
Gillian Lieberman, MD
Patient #4: Colon CA
Abdominal CT findings:
Courtesy of Dr. Vincent Chan, BIDMC
Seroma
Rib end?
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Janet McLaren
Gillian Lieberman, MD
Patient #4: Colon CA
?
Rib end
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #4: Colon CA
As Abdominal CT was inconclusive, the patient was referred to
Nuclear Medicine for a PET Scan.
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #4: Colon CA
PET Scan revealed uptake in the chest wall scar, consistent with
seeding during removal of the liver metastasis and recurrence.
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #4: Colon CA
PET Imaging of the pelvis revealed another site of recurrence at
the removal site of the primary tumor.
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #4: Colon CA
PET Imaging of the pelvis revealed another site of recurrence at
the removal site of the primary tumor.
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #4: Colon CA
• Diagnosis
– Highly sensitive in identifying colonic lesions, but not
very specific (100% and 43%)
• Staging
– Good for evaluating distant metastases; lymph nodes to
close to primary tumor to see
• Follow-up
– CTs are difficult to evaluate in the post-op patient due
to fibrosis and distorted anatomy
– PET Scans are very useful in follow-up patients by
identifying recurrent lesions in areas of scar tissue
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Janet McLaren
Gillian Lieberman, MD
Keeping a DDx
FDG identifies
hypermetabolic cells
Malignancy
Infection
Inflammation
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Janet McLaren
Gillian Lieberman, MD
Lets review some positive PET
scans that were NOT due to
malignancy
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Janet McLaren
Gillian Lieberman, MD
Patient #5
• 60 year old female
• Referred for evaluation
of a SPN in the right upper
lobe
RV
LV
?
Cross-section at T9 level
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #5
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #5
Hiatal
Hernia
 Increased
metabolic
activity from
inflammation
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Patient #6
• 41 year-old man
• History of
hepatocellular
carcinoma
• Chevron Incision
 Increased
metabolic activity
of healing tissue
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Courtesy of Dr. Vincent Chan, BIDMC
Janet McLaren
Gillian Lieberman, MD
Summary
• PET is one of the most exciting fields in modern
Nuclear Medicine
• When used in correlation with anatomic imaging,
PET can provide important physiologic information
• The modality has become very useful in the diagnosis,
staging, and follow-up of oncologic disease
• Great opportunity for advances in PET imaging:
– isotopes tailored for specific cancers
– new detectors to improve image resolution
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Janet McLaren
Gillian Lieberman, MD
Acknowledgements
• Vincent Chan, MD and the Nuclear Medicine
Department of the BIDMC
• Gillian Lieberman, MD
• Pamela Lepkowski
• Larry Barbaras and Cara Lyn D’amour,
our Webmasters
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Janet McLaren
Gillian Lieberman, MD
References
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•
•
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Bar-Shalom R, Valdivia AY, Blaufox MD. PET Imaging in Oncology. Sem Nuc
Med 2000; 30(3): 150-185.
Bax JJ, Patton JA, Poldermans D, Elhendy A, and Sandler MP. 18Fluorodeoxyglucose imaging with Positron Emission Tomography and Single
Photon Emission Computed Tomography: Cardiac Applications. Sem Nuc Med
2000; 30(4):281-298.
Delbeke D, Martin WH. Positron Emission Tomography Imaging in Oncology.
Rad Clin NA 2001 Sept; 39(5): 883-917.
Saunders CA, Dussek JE, O'Doherty MJ, Maisey MN. Evaluation of fluorine-18fluorodeoxyglucose whole body positron emission tomography imaging in the
staging of lung cancer. Annals of Thoracic Surgery1999 Mar; 67(3):790-7.
Schwartz B and Udelson JE. Assessment of myocardial viability by nuclear imaging
in coronary heart disease. Up-to-Date version 9.3, 2001.
Stark P. Computed Tomography and Positron Emission Tomographic scanning of
pulmonary nodules. Up-to-Date version 9.3, 2001.
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