A Prospective Study on Tumor Hypoxia Kinetics to Implement Hypoxic Imaging-Guided IMRT

Diana Stripp, MD
University of Pennsylvania Cancer Center
Last Modified: November 6, 2001

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Presenter: Chao, KS
Presenter's Affiliation: Radiology, Washington University, St. Louis, St. Louis, MO
Type of Session: Scientific

Background

  • 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.

    Results

  • 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.

    Author's Conclusions

  • 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.

    Clinical/Scientific Implications

  • 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

    Oncolink's ASTRO Coverage made possible by an unrestricted Educational Grant from Bristol-Myers Squibb Oncology and Pharmacia Oncology.


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