A Prospective Study on Tumor Hypoxia Kinetics to Implement Hypoxic Imaging-Guided IMRT
Presenter: Chao, KS
Presenter's Affiliation: Radiology, Washington University, St. Louis, St. Louis, MO
Type of Session: Scientific
Unsatisfactory local/regional tumor control for locally advanced cancers with radiation therapy is in part associated with the phenomenon of tumor hypoxia.
There is a lack of non-invasive and reproducible methods to identify hypoxia in human tumors.
This study was designed to evaluate a Positron emission tomography (PET) imaging-based hypoxia measurement technique employing a Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM) tracer
This information was used to evaluate hypoxia image guided Intensity modulated radiation therapy (IMRT).
Materials and Methods
16 pts with head and neck carcinoma were prospectively enrolled in this study.
A co-registration system with CT and PET was integrated into the thermoplastic immobilization head mask for image fusion.
Gross tumor volume (GTV) was delineated based on physical and radiological findings.
HGTV - hypoxic tumor volume was guided by ATSM.
Cu-ATSM PET scan was performed before RT, at 20 Gy, and at 40 Gy to study the evolution of tumor hypoxia.
Imaging distortion after CT and PET image co-registration were within 2 mm.
ATSM-avid or hypoxic tumor sub-volume (hGTV) was successfully defined using the CT/PET imaging fusion.
We further demonstrate the feasibility of Cu-ATSM-guided IMRT by showing that the radiation dose to the hGTV could be escalated without compromising normal tissue (parotid glands and spinal cord) sparing.
Tumor hypoxia evolution was observed during the course of RT.
Cu-ATSM-guided IMRT approach through co-registering hypoxia 60Cu-ATSM PET to the corresponding CT images for IMRT planning is feasible.
Information on tumor hypoxic kinetics will expand our understanding of target volume uncertainty before implementing this novel therapeutic approach to patients with locally advanced tumor.
This imaging guided approach to IMRT can further assist in definition of target volume and may allow dose escalation with normal tissue sparing.
It remains unclear if dose escalation to hypoxic regions of a tumor will improve outcomes of treatment
This is a very interesting area of research that deserves continued evaluation
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