Primary Outcome Measures:
- Tumor stage change from Computed Tomography (CT) perfusion measurement [ Time Frame: 3 months ]
Secondary Outcome Measures:
- Tumor perfusion as measured by perfusion CT. [ Time Frame: 1 year ]
If the patient undergoes surgery to remove the lesion in the rectum, the surgical specimen will be examined by the pathologist, who will perform a variety of tests to detect evidence of new blood vessel growth. The sample will be stored per routine protocol of the Stanford Department of Pathology.
Recent advances in computed tomography (CT) technology have made CT perfusion imaging feasible for the assessment of tumor perfusion in solid tumors of the abdomen. CT perfusion has shown promising results in serving as a noninvasive method of predicting response to therapy in cancer patients. CT perfusion parameters have also been found to correlate with immunohistologic markers of angiogenesis in a number of solid tumors, suggesting a possible role for CT perfusion as a noninvasive biomarker of tumor angiogenesis. The goals of the investigators study are twofold: first, to determine the relationship between baseline CT perfusion characteristics of rectal cancers and their response to treatment, and second, to determine if perfusion CT can be used to subsequently monitor tumor response to treatment. The investigators hope to enroll those patients with locally advanced rectal cancer undergoing standard CT for pre-treatment planning, integrating CT perfusion imaging into the current abdomen/pelvis imaging protocol with close clinical and radiologic follow-up after treatment to determine response to therapy and time to disease progression.