MI techniques recommend against unnecessary surgeries and monitor therapy
Use of FDG-PET for cervical cancer staging and therapy monitoring was approved by Medicare in January 2005, but its adoption remains rare, despite research results that strongly support the application.
"Since its approval by Medicare, the use of PET [for cervical cancer] has increased but not by much," said Dr. Perry Grigsby, a professor of radiation oncology at Washington University in St. Louis.
FDG-PET can detect tumors that would otherwise remain undetected by conventional strategies, such as surgery or CT. Grigsby and colleagues demonstrated this in a 2001 study of 101 women with cervical cancer. PET scans detected cervical tumors in almost all of the women, whereas CT scans revealed only about 75%. Elsewhere in the body, PET scans consistently identified lymph node tumors more often than CT scans.
The treatment implications are significant. For 47 women, CT scans showed cervical tumors but no spread to pelvic lymph nodes. Based on this information, standard treatment could include surgical removal of the tumor. But by using PET, abnormal pelvic lymph nodes were discovered. Recommended treatment based on this additional information might be different, focusing on radiation therapy, for example, instead of surgery.
PET is also valuable for tracking response to cervical cancer treatment, Grigsby said. If after three months of treatment a patient's PET scan shows no FDG uptake, that patient has a 90% chance of full recovery.
Additionally, evidence from a prospective trial at Denmark's Copenhagen University Hospital showed that FDG-PET/CT improves cervical cancer staging accuracy and creates opportunities for additional radiation therapy to treat otherwise undetected cancer metastasis. According to Dr. Annika Loft, chief physician at the hospital's Center for Diagnostic Investigations, performing PET/CT increases the probability of finding para-aortic nodal disease, known to appear in 24% of cervical cancer patients.
Despite such promising results, adoption of the technique has been slow. Historically, CT and surgery have been used to determine extent of cervical cancer. But according to Grigsby and others, these traditional methods have significant limitations.
"Surgical staging is rather barbaric in 2006," he said, noting the invasiveness of surgery compared with relatively noninvasive imaging techniques.
According to Dr. Eugene Toy, director of gynecologic oncology research at the University of Rochester Medical Center, PET is valuable in determining when surgery can be avoided. Surgery could delay crucial radiation treatment due to possible surgical complications and the need to wait for patients to heal before administering radiation.
"Why subject the patient to such a radical procedure if they are going to need radiation anyway?" he said.
If the disease is widespread, then doctors could focus on palliative care instead of potentially difficult and ongoing treatment, he said.
Even so, PET scans for cervical cancer aren't very common at many clinics. At the Northern California Pet Imaging Center, they make up a small fraction of the PET scans performed.
"Medicare approval didn't drastically change our business," said Ruth Tesar, executive director.
Dr. Daniel Lee, associate director of PET/CT imaging at the University of Rochester Medical Center, reports that his center has performed three PET scans for cervical cancer patients in the past year, and all three were requested by the same radiation oncologist.
"Reimbursement is relatively new, so there may be a lack of awareness about the technology," he said. "Clinicians just aren't used to using PET scans."
Lee also suggests that certain geographical regions might be more reluctant than others to adopt new technologies. Time is required for a new technique to be adopted by physicians, and office personnel need training in the relevant reimbursement issues.
But Lee is optimistic about the power of PET for cervical cancer staging. It can recognize abnormalities not visible on CT or MR scans, and it can be used to monitor treatment, ensuring that cancer is not over- or undertreated, he said.