Study Using Fluorine-18-Labeled Fluoro-Misonidazole Positron Emission Tomography to Detect Hypoxia in Locally Advanced (T3-T4 and./or N1)Primary Rectal Cancer Patients

A Feasibility Study Using Fluorine-18-Labeled Fluoro-Misonidazole Positron Emission Tomography to Detect Hypoxia in Locally Advanced (T3-T4 and./or N1)Primary Rectal Cancer Patients

When used with a different radioactive tracer called FMISO, a PET scan can find areas of low oxygen in the tumor. We think that having areas of low oxygen is a reason why some tumors are hard to treat with radiation.

In a past study, FMISO PET scans were performed in 6 patients with rectal cancer that could not be operated on and that had spread to other areas. In this group of patients, FMISO PET scans were able to find the low oxygen areas in their tumors. But this study included only a few patients. In the present study, we want to use FMISO PET scans in patients who have tumors that can be operated on. This group of patients will have radiation, chemotherapy or both before they have their surgery. We want to see if FMISO PET can find low oxygen areas in this distinct group of patients.

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.

Inclusion Criteria:

• Able to provide written informed consent
• Histologically confirmed diagnosis of Stage 2 or Stage 3 rectal carcinoma requiring preoperative radiation, chemotherapy or both, per treating physician
• 18 years of age or older
• Karnofsky performance status ≥ or = to 70

Exclusion Criteria:

• Women who are pregnant (confirmed by serum b-HCG in women of reproductive age) or breast feeding