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.
FMISO PET scans have been done in 6 patients with rectal cancer. These patients had 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.
Primary Outcome Measures:
- 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 ]
Secondary Outcome Measures:
- 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 Btw 1 & 3 cc of blood will be taken at each time point (making the max volume of blood withdrawn during this study 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 ]
| Estimated Enrollment: |
30 |
| Study Start Date: |
December 2007 |
| Estimated Study Completion Date: |
December 2010 |
| Estimated Primary Completion Date: |
December 2010 (Final data collection date for primary outcome measure) |
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1: Experimental
FMISO PET study.
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Radiation: Fluorine-18-Labeled Fluoro-Misonidazole Positron Emission
You will be scanned three times on the same day. The 1st scan will last about 30 minutes. Then have an hour to wait before you are scanned again. The second scan will last about 10 minutes. You have between one and two hours to wait before you are scanned again. The third & final scan will also last about 10 minutes. During the PET scan, you will have a separate i.v. line put into your other arm so that we can take blood samples. These samples will be less than half a teaspoon each. We are taking these blood samples to see how your body responds to FMISO. Up to a maximum of 3 blood samples will be obtained using the second I.V. line immediately at selected times post injection and during the PET scan procedure. Samples will be taken (i) btw 2-40 post injection, (ii) btw 80-100 minutes post injection and (iii) btw 110- 140 minutes post injection. Between 1 and 3 cc of blood will be removed at each time point (making the maximum volume of blood withdrawn during this study < 9 cc).
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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.
Purpose
