Colon Cancer and PET/CT

Colorectal cancer affects 1 person in 20 in the US and Europe. The ACS estimates that 107,300 new cases of colon cancer and 41,000 new cases of rectal cancer in the United States in 2002. Colorectal cancer will be responsible for about 56,600 deaths in 2002.

The good news is that the death rate from colorectal cancer has been going down for the past 20 years. This may be because more of the cases are found early, and also because treatments have improved. About 70% of patients diagnosed with colorectal cancer will undergo surgery although one-third of these patients will develop recurrence some time after surgery.

As with all types of cancer, early diagnosis of colorectal cancer is key to its cure. Colorectal cancers probably develop slowly over a period of several years. Before a true cancer develops, there are often earlier changes in the lining of the colon or rectum. If found early, before it has metastasized, the disease is considered curable. However, as the tumor spreads to lymph nodes, a patient's chance of living at least five years drops to 40 - 60%. If the cancer has already spread to distant organs, the long-term survival is much lower.

Before PET, it was extremely difficult to monitor for suspected recurrence. The other techniques available for staging and assessment of potential recurrences lack sensitivity and precision and frequently result in diagnostic and therapeutic delays. In many colorectal patients, pelvic CT will demonstrate a suspicious mass, but cannot distinguish mass tumor recurrence from postoperative or postradiation scar. Further evaluation usually involves a biopsy. A positive biopsy is highly predictive of recurrence but because it is impossible to sample the entire mass, a negative biopsy cannot exclude recurrence.

How Does PET/CT Make a Difference

Whole-Body PET imaging is the most accurate diagnostic test for detection of recurrent colorectal cancer, and is a cost-effective way to differentiate resectable from non-resectable disease. A PET scan is indicated whenever a major management decision depends upon accurate evaluation of tumor presence and extent.