• the feasibility of a non-invasive method of detecting hypoxia, using FMISO-PET imaging in colorectal cancer patients. [ Time Frame: three times on the same day. ] [ Designated as safety issue: No ]
  

• determine volume of hypoxic tumor ROIs as a proportion of the entire tumor volume by this non-invasive imaging technique. ROIs are defined as those voxels, within the tumor volume defined on FDG PET/CT, for which the 18F-FMISO radioactivity concent [ Time Frame: prior to FMISO injection, btw 2-40 min post injection, (ii) btw 80-100 min post injection & (iii) btw 110- 140 min post injection. Btw 1 & 3 cc of blood will be taken at each time point (making the max volume of blood withdrawn during this study < 9 cc). ] [ Designated as safety issue: No ]
  

Hypoxia is a characteristic feature of malignant solid tumors associated with poor prognosis and resistance to chemotherapy and radiation. It has also been shown (6) that the presence of hypoxia may reduce long-term survival post surgery. Hypoxia renders tumor cells up to three times more resistant to ionizing radiation than aerobic cells. The presence of hypoxic regions within tumors may be one factor leading to local failure after treatment with standard pre-operative radiotherapy doses. If these regions could be identified and verified using a non-invasive imaging technique prior to surgery, they could be specifically targeted using sophisticated planning techniques such as intensity modulated radiation therapy (IMRT) to deliver higher doses ionizing radiation with preoperative radiotherapy. Future studies using IMRT to "dose paint" areas of hypoxia within tumors will build upon the results of this feasibility study. Ultimately, by the delivery of differential dose of radiation to the tumor, in combination with surgery, the local control rates of rectal cancer patients may further be improved.