Female Advantage
A powerful imaging technique that provides unique information about a patient's body is contributing to better outcomes in WOMEN'S cancers.
A medical diagnosis is only as good as the information used to make it-and Keck School of Medicine of USC radiologists are finding that using PET scans for follow-up in women's cancers appears to make diagnoses more accurate.
PET, or positron emission tomography, is a powerful imaging technique that provides unique information about a patient's body that is unavailable through other kinds of scans. In the world of cancer,
radiologists can use it to find out how advanced the disease is when it is first diagnosed. It also can detect places cancer might have spread. And radiologists increasingly use PET during a patient's treatment to see if chemotherapy is working, as well as after treatment to see if cancer has returned.
Hossein Jadvar, M.D., Ph.D., assistant professor of radiology and biomedical engineering at the Keck School of Medicine, says PET holds great promise for contributing to better outcomes in gynecologic and breast cancers.
"PET has been demonstrated to be useful as a powerful adjunct to other traditional imaging techniques in evaluating a variety of cancers in women," Jadvar notes. Increasingly, studies show that it also is cost-effective, allowing patients to avoid unnecessary tests and therapies.
To detect cancer, PET is used in partnership with a chemical called [F-18] fluorodeoxyglucose, or FDG, a form of sugar marked with a radioactive tracer.
Here is how it works: After radiologists inject FDG into a patient, a PET scan shows if there are any hot spots in the patient's body where the sugar is being metabolized quickly. These spots may indicate cancer, Jadvar explains, because cancerous cells use sugar more than healthy cells.
"FDG-PET relies on physiology by detecting increased metabolic activity in tumors," Jadvar explains.
At a meeting of the Radiological Society of North America, Jadvar and colleague Peter S. Conti, M.D., Ph.D., associate professor of radiology at the Keck School and director of the USC PET Imaging Science Center, presented a study on their use of PET with cervical cancer patients.
Cervical cancer is one of the most common tumors in women. Because of the Pap test, overall deaths due to cervical cancer have declined over the years. The Pap test allows physicians to find many cancers at an early stage, and early stage cervical cancer can be successfully treated. Unfortunately, though, deaths due to invasive cervical cancer have not declined.
The time a woman remains free from cancer after her initial treatment (usually consisting of surgery, radiation and chemotherapy) depends on the stage of her cancer when detected and whether her treatment was adequate for the extent of the cancer. Obviously, then, it is important that physicians get accurate clues to where cancer has spread before they create a patient's treatment regimen.
In their study, Jadvar and Conti used PET to look for signs of recurrent or metastatic cancer in a group of women who had already been treated for cervical cancer. In some cases, the PET scans were able to detect cancer recurrence that was not seen through other methods.
The radiologists performed PET scans in seven women who were referred for follow-up between two months and five years after their initial treatment, after abnormal test results aroused suspicion that their cancer might have spread. Besides PET, the women received magnetic resonance imaging (MRI) and computed tomography (CT) scans, as appropriate. In four cases, the PET scans confirmed findings from the other scans. But in three of the women, the PET scans found evidence of cervical cancer metastasis, or spread, that the CT or MRI studies did not show.
MRI and CT scans are extremely valuable in the quest to seek out cancer sites in the body: They provide a picture of organs, showing slices of the body in detail. But many cancer imaging experts have shown that these anatomic studies have limitations. They cannot always tell the difference between remaining or recurrent cancer and the physical changes caused by scarring and healing found within a patient's body after cancer treatment.
Among the study patients with cancer identified through PET, one had signs of extensive cancer in the lungs as well as a blood clot in the heart. Another patient had a mass in a lung, while the other had cancer spread in the abdomen and pelvis.
The preliminary results in a small group of patients indicate that FDG-PET is useful in re-evaluating women with cervical cancer after therapy, Jadvar notes. Further study with more patients is needed to determine the appropriate role of FDG-PET in the cervical cancer setting, he adds.
In ovarian cancer-one of the most deadly cancers, because it is usually in an advanced stage when found-radiologists often use PET to watch for signs of remaining cancer after a patient is treated or to look for recurrent disease. And though studies of PET in uterine cancer are limited, Jadvar says, PET may turn out to prove useful in tracking down otherwise-cloaked signs of spread in that cancer, too.
In the field of breast cancer, PET stands as a valuable partner to standard tests such as ultrasound and mammography.
"PET can distinguish malignant from benign breast lesions and is particularly useful in patients with dense breasts or with breast implants, where mammography is limited," Jadvar says.
At diagnosis, about 60 percent of breast cancer patients have cancer that has metastasized to the axillary lymph nodes-a chain of glands stretching from the underarm to the collarbone. Although the standard for diagnosis includes surgically removing and checking these nodes, FDG-PET can help detect such metastases as well. It also is useful in finding out whether cancer has spread to the bones, as well as other sites such as the liver and far-away lymph nodes.
PET also has been shown to be useful during therapy. Oncologists may use it to see whether patients are responding to treatment. If treatment is not helping, therapy may be modified.
"PET may also find a role in surveillance of asymptomatic patients for early detection of recurrent disease, despite no clinically evident disease," Jadvar says.
According to Conti, the Center for Medicare/Medicaid Services recently approved reimbursement for evaluation of breast cancer in patients requiring staging or restaging of advanced disease and for reassessment of response to therapies.
The addition of breast cancer as a Medicare covered procedure increases the spectrum of cancers already covered, including non-small cell lung, esophageal, colorectal, lymphoma, melanoma, and some head and neck cancers. Many private insurers already cover PET for most cancers.
Jadvar adds: "We now routinely scan four to five patients a day. This parallels increased awareness among referring physicians and patients, in response to an increasing number of clinical studies on the usefulness of PET."
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