Colorectal cancer occurs when certain cells within the large intestine grow in an uncontrolled, abnormal, manner. Cancer that begins in the last 6-8 inches of the colon is called rectal cancer. Together, they are often referred to as colorectal cancer.
A 64 year-old female patient with colorectal cancer restaged for tumor reccurrence 6 months after chemotherapy. Tumor markers and CT scan were negative for tumor recurrence. FDG PET images show large focus of increased tracer uptake suggesting mesenteric lymph node involvement (arrows). Management was changed from no therapy to chemotherapy.
According to estimates from the American Cancer Society, more than 149,500 new cases of colon and rectum cancer will be diagnosed in the United States and more than 52,980 people will die from the disease in 2021. In the United States, colorectal cancer is the third leading cause of cancer-related deaths in men and in women, and the second most common cause of cancer deaths when men and women are combined.
New developments in molecular imaging technologies are dramatically improving the ways in which colorectal cancer is diagnosed and treated. Research in molecular imaging is also contributing to our understanding of the disease and directing more effective care of patients with colorectal cancer.
Positron emission tomography (PET) scanning and PET combined with computed tomography (PET-CT) is used for colorectal cancer.
PET involves the use of an imaging device (PET scanner) and a tiny amount of radiotracer that is injected into the patient’s bloodstream. A frequently used PET radiotracer is 18F-fluorodeoxyglucose (FDG), which the body treats like the simple sugar glucose. It usually takes between 30 and 60 minutes for the FDG distribution throughout the body to become fixed. A CT is also obtained on the same machine so the FDG and CT scans can be fused together and compared.