Whole-body positron emission tomography (PET) three months after completion of therapy for cervical cancer can identify which patients have had complete responses to treatment, according to an article in the November 21 issue of the Journal of the American Medical Association.

The study was conducted at Washington University School of Medicine in St. Louis, Missouri (USA).

"This is the first time we can say that we have a reliable test to follow cervical cancer patients after therapy," said Julie K. Schwarz, MD, PhD, a Barnes-Jewish Hospital resident in the Department of Radiation Oncology. "We ask them to come back for a follow-up visit about three months after treatment is finished, and we perform a PET scan. If the scan shows a complete response to treatment, we can say with confidence that they are going to do extremely well. That's really powerful."

Cervical cancer tissue glowed brightly in the scans used in the study, called FDG-PET scans, because tumor tissue trapped significantly more of the radioactively tagged glucose tracer than normal, health tissue.

The prospective study involved 92 women who were treated with external radiation, brachytherapy, or concurrent chemotherapy between January 2003 and September 2006. Post-therapy scans were done two to four months (mean, three months) after completion of therapy.

Primary outcome end points were metabolic response, progression-free survival, and cause-specific survival. Post-therapy scans showed a complete metabolic response in 65 patients (70 percent), a partial metabolic response in 15 (16 percent), and progressive disease in 12 (13 percent). Their three-year progression-free survival rates were 78 percent, 33 percent, and 0 percent, respectively.

Multivariate analysis demonstrated that the hazard ratio for risk of recurrence based on the post-therapy metabolic response showing progressive disease was 32.57 (95 percent confidence interval [CI], 10.22-103.82). A partial metabolic response had a hazard ratio of 6.30 (95% CI, 2.73-14.56). Both were more predictive of survival outcome than pretreatment lymph node status (hazard ratio, 3.54; 95% CI, 1.54-8.09).

Not only can post-treatment scans reassure patients whose tumors responded well to therapy, they can identify patients whose tumors have not responded so that their physicians can explore other treatment options before the cancer advances further. These options can include surgery to remove tissue, standard chemotherapy or experimental therapies available through clinical trials.

"Follow-up PET scans can also be very useful tools for physicians conducting clinical trials of new therapies," Schwarz said. "Our study has shown that the scans are predictive of long-term survival. Using PET scans, clinical researchers can get an early readout of how effective experimental treatments might be."

Schwarz and colleagues also have a project to compare follow-up PET results with tumor biology to find out why some tumors don't respond well to therapy. In a study that won her a Resident Clinical Basic Science Research Award from the American Society for Therapeutic Radiation and Oncology, a global organization of medical professionals, Schwarz found differences in gene activity between tumors from patients that responded well and those that had persistent disease. Ongoing research will look for the significance of these differences.

The study's senior author, Perry Grigsby, MD, professor of radiation oncology, of nuclear medicine and of obstetrics and gynecology and a radiation oncologist with the Siteman Cancer Center at Washington University School of Medicine and Barnes-Jewish Hospital, has overseen a patient database that now has PET images and tumor samples from hundreds of cervical cancer patients.

"We have a tremendous database of PET images collected from patients in the department since 1998," Schwarz said. "We want to combine these results with analyses of tumor biopsies so that we can more effectively choose additional therapies for patients who haven't responded to the initial treatment."