April 22, 2009 > PET/CT Scans Help Patient Avoid Unnecessary Biopsies, Improve Accuracy of Treatments
PET/CT Scans Help Patient Avoid Unnecessary Biopsies, Improve Accuracy of Treatments
Like many other people, Michael Peterson delayed having a colonoscopy screening at the recommended age of 50. A physically fit pilot for United Airlines who worked out regularly at the gym and had no family history of colon cancer, Peterson had little reason to believe he was at risk. At age 55, though, he noticed a small amount of blood in his stool in July 2007 and scheduled a colonoscopy right away. The diagnosis was cancer.
Peterson's physicians performed a successful colon resection surgery to remove the tumor in August 2007. He then received follow-up radiation therapy for six weeks, followed by six months of chemotherapy until April 2008.
"After the chemo, everything went fine - including a CT scan in August that showed no signs of tumors," he recalls. "Then in November, I went in for another three-month follow-up exam, and a CT scan showed two spots on my liver and some spots on one of my lungs. The interventional radiologist tried to biopsy the spots on the liver, but due to their location, they were difficult to reach and the biopsy was inconclusive."
Peterson's oncologist, Dr. Vandana B. Sharma, who is on staff at Washington Hospital, encouraged him to have a PET (positron emission tomography) scan to evaluate the liver and lung spots.
"A CT (computed tomography) scan produces detailed views of the internal organs and structures of the body, but it doesn't show the activity of those structures," she explains. "A PET scan shows how active the cells, tissues and organs are. This is important because cancer cells are more metabolically active than normal cells. Combining the information from a PET scan with images from a CT scan allows us to determine the exact location of any abnormally active tissues."
A CT scan produces multiple X-ray images of the body in "slices" that are less than a millimeter in width. Those images are fed into a computer to produce a three-dimensional picture of the organ or area of the body being examined. The CT scan gives superb anatomic detail of even very small internal body structures.
A PET scan is a type of nuclear medicine imaging that measures the metabolic activity of tissues. With a PET scan, a glucose solution with a small amount of a radioactive "tracer" material is injected into a vein. The tracer travels through the body and is absorbed by the organs and tissues being studied, where it gives off energy that is detected by the PET scanner. Because cancer cells tend to metabolize sugar more rapidly than normal cells, the glucose used in PET scans accumulates more readily in the abnormal tissues.
"The PET scan showed that the spots on my lung were not metabolically active," Peterson says. "That was a distinct advantage, because it meant they did not have to perform biopsies of the lung.
"Unfortunately, the PET scan also showed that the spots on the liver were cancerous," he adds. "Even thought that was not the diagnosis I had hoped for, I am sure the PET scan saved me from having to undergo a more in-depth biopsy of the liver. The PET and CT scans also gave the surgeons very accurate information that enabled them to remove the liver tumors laparoscopically, with good clear margins, in December. I am now on follow-up chemotherapy."
In January, Washington Hospital and Alliance Imaging installed a new, state-of-the-art PET/CT scanner on site. The PET/CT scanner fuses the data from the PET scan with images from a CT scan to provide physicians with a powerful diagnostic and treatment-management tool.
Sharma notes that PET/CT scans are very useful for diagnosing and treating lymphoma as well as many other types of solid malignancies. "PET scans can help us determine if cancer has spread through the body," she says. "With lymphoma, we also use PET scans after two or three treatments to see if the tissue is still metabolically active - meaning it's still cancerous - or whether it is just scar tissue. Without PET scans, we would have to biopsy the tissue to see if it was cancerous, so the scans can spare patients from unnecessary procedures."
Another patient of Sharma's had a CT scan that showed a small nodule in the lung and another nodule on the adrenal gland. "A PET scan showed that the nodule on the adrenal gland was benign, not active," she says. "Because of this, the patient was diagnosed with stage 1 lung cancer, rather than stage 4, so she was able to have surgery for the lung tumor and is now cancer-free."
PET scans are not painful, according to Peterson. "The injection of radiated glucose is like a regular shot," he says. "You do have to sit still, relax and stay quiet for about 30 minutes while the tracer moves through your body. My scans took about 35 minutes to go from the eyes to the knees. The only discomfort I experienced was having to remain still, with my arms above my head."
Despite that minor discomfort, Peterson is grateful for the PET scan technology. "Not having a PET scan certainly would have complicated my diagnosis," he says. "I think it made a big difference in helping the surgeon perform the liver surgery properly, not to mention not having to do a biopsy of the spots on my lung. There are times when I wonder what my future holds, but I have gotten positive feedback from my doctors on the prognosis."
Each year, April is designated as Cancer Control Month to highlight advances in cancer treatment and encourage people to follow established guidelines for cancer screenings. If you are over age 50, consult your physician about scheduling a colonoscopy as well as any other recommended screenings. For more information about PET/CT scans, please visit www.petscaninfo.com.