Response Evaluation for FDG PET/CT

progressive tumors

Increase in tumor glucose use and volume of tumor cells can be expected in __________—-_

• Breast Cancer

• Lung Cancer

• Esophageal Cancer

• Osteosarcomas

A reduction in FDG uptake has been shown to indicate treatment response and/or improve survival in patients with solid tumors such as:

inaccurate

CT is _____________ in differentiating viable tumor from surrounding necrotic or fibrotic tissue; consequently the degree of response may be underestimated on CT.

full kinetic metabolism

• yields an absolute rate of FDG metabolism

• independent of imaging time

• provides insights into various components of glucose metabolism such as transport and phosphorylation.

The Standardized Uptake Value (SUV)

semi-quantitative method most commonly used to determine FDG uptake in attenuation corrected PET images.

90 mins

In most malignant tumors, FDG uptake increases continuously for at least ____________ after FDG injection and is usually significantly higher at later time points.

2 hours

FDG uptake usually plateaus after _______ but may plateau earlier following therapy

elevated plasma glucose

__________________ FDG uptake tends to be lower for diabetic patients due to

• FDG dose extravasation

• Failure to apply decay correction

• Poor Calibration of counting equipment

• Partial volume effects

• Different Reconstruction methods across vendors

Common Errors in response evaluation

paravenous injection

A _______________ of FDG decreases the amount of tracer available for uptake by the tumor and can result to incorrectly low SUVs.

good prognosis.

The rapid disappearance of FDG uptake is a sign of

PERCIST

specifies the percentage change in metabolic activity

Standard uptake value

The primary determinant of response using PERCIST is the _____________

single most active lesion

PRECIST specifies that SUL peak is to be obtained from a _______________ each scan.

Complete Metabolic Response

Disappearance of metabolic tumor activity of both target and non-target lesions.

Partial Metabolic Response

Decline >30% in SUL peak with at least 0.8 unit decline in SUV

Progressive Metabolic Diseas

Includes an increase of >30% in SUL peak with at least a 0.8 unit visible increase in FDG uptake. 

Stable Metabolic Disease

The absence of change or mild changes that do not meet minimum qualifications of other categories.

Total Glycolytic Value (TGV)

• An alternative index that can be used to measure global changes in tumor glycolysis

• is the volume of the lesions determined by the PET FDG images by an adoptive technique

Non-hematological solid tumors

These tumors are more resistant to chemotherapy and radiation therapy than are malignant lymphomas and changes in tumor glucose metabolic activity are smaller and occur more slowly than in lymphomas.

Mediastinal blood pool

For lymphoma, _____________________ is recommended as the reference background activity to define FDG PET positivity for a residual mass >2cm in the greatest traverse diameter, regardless of its location.

Interim PET/CT

done both for assessing chemosensitivity and for individual response adapted treatment modification in lymphoma

cytostatic therapies

While FDG has been used extensively for the evaluation of cytoreductive therapies, there is only limited experience in using FDG as a marker of response in ______________________