Tests to Evaluate Response of GIST Treatment

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Tyrosine Kinase
Inhibitors

Response Evaluation

Radiologic Evaluation

Tests Oncologists
Should Order

Other Treatments

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Tests the Oncologist Should Order to Evaluate TKI Treatment Response

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Essential imaging techniques used in the evaluation of response to TKI therapy in GIST:

Computed tomography (CT) with contrast:

the standard imaging modality in GIST; provides information on tumor size and density

Fluorine-18-fluorodeoxyglucose positron emission tomography (FDG-PET):
measures glucose uptake; provides information about the metabolic activity of tumors. It can differentiate active tumor from necrotic/inactive scar tissue, malignant tumor from benign tumor, and recurrent tumor from benign changes

FDG-PET scans should be used in addition to CT scans but not as a replacement¹
These scans are useful for resolving ambiguous CT findings and have also been shown to be predictive of outcome, especially in patients who have stable disease while on TKI treatment²

The integration of FDG-PET and CT, as in combined hybrid PET/CT scanners, has not only optimized the evaluation of patients with GIST treated with molecularly targeted drugs, but may ultimately help shorten clinical trials and accelerate drug development in this disease as well.^2,3

Guidelines for Follow-up Imaging

CT scans and FDG-PET scans should be ordered prior to every follow-up visit when response to TKI therapy in a KIT+ GIST patient is being evaluated. The NCCN Treatment Guidelines for GIST recommend follow-up imaging of patients with GIST as follows³:

Baseline imaging should include CT and PET scans
- A second PET to evaluate initial response to TKI treatment can be considered within 2 to 4 weeks of treatment initiation
In patients with unresectable or incompletely resected GISTs receiving TKI treatment, follow-up CT scans are recommended every 3 to 6 months
In patients with completely resected GISTS, follow-up CT scans are recommended every 3 to 6 months for the first 5 years, and annually thereafter¹

Learn more about evaluation of response to treatment.

National Comprehensive Cancer Network Clinical Practice Guidelines in Oncology: Soft tissue sarcoma. v.2.2008. http://www.nccn.org/professionals/ physician_gls/PDF/sarcoma.pdf. Accessed November 24, 2008.
Van den Abbeele, Annick D. The Lessons of GIST—PET and PET/CT: A New Paradigm for Imaging Oncologist 2008 13: 8-13; doi:10.1634/theoncologist.13-S2-8
Demetri GD, Benjamin RS, Blanke CD, et al. NCCN task force report: management of patients with gastrointestinal stromal tumor (GIST) – update of the NCCN clinical practice guidelines. J Natl Compr Canc Netw 2007;5[Suppl 2]:S1-S29.

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