PET Predicts Outcomes for Glioma, Colorectal Cancer Tx

PET scans can indicate the effectiveness of therapies among patients receiving treatment for glioma, a malignant brain cancer, and for those with locally advanced rectal cancer, according to two studies presented at the Society of Nuclear Medicine’s Annual Meeting in Miami Beach, Fla.

In the first study, from the UCLA David Geffen School of Medicine in Los Angeles, Calif., researchers found that molecular imaging with F-18-FDOPA PET scans, combined with an amino acid imaging probe gauged whether glioma was still active as early as two weeks after the start of treatment, without use of an invasive biopsy.

Thirty patients with recurrent high-grade gliomas underwent F-18-FDOPA PET scans immediately before treatment with bevacizumab combination therapy. They were scanned again at two and six weeks after therapy.

Researchers compared the PET scans with MRI images, looking for treatment response. They found that patients who responded positively to treatment, as evidenced with the PET imaging, lived three times longer than those who responded poorly since the start of treatment.

“It is especially important to be able to tell whether a treatment is effective in patients with this cancer because it is extremely malignant - the typical life expectancy is only about one year,” said Wei Chen, MD, PhD, an associate clinical professor of molecular and medicinal pharmacology for the Ahmanson Biological Imaging Center at the university. “There is currently no reliable non-invasive tool to predict treatment response in patients with malignant gliomas. The availability of molecular imaging methods like this one using amino-acid positron emission tomography is crucial for a rapid and accurate prediction of treatment outcomes.”

In the second study, from Napoli, Italy, researchers found that molecular imaging biomarkers can be used to approximate how an experimental radiochemotherapy will work as treatment for locally advanced rectal cancer.

Forty-six patients with locally advanced rectal cancer with poor prognosis received three courses of chemotherapy during external radiation therapy. They also received bevacizumab four days before the two first courses of chemotherapy. Researchers scanned the patients three times (before treatment, after 12 days and again after surgery) using PET/CT with F-18 fluorodeoxyglucose (FDG). Thirty-seven patients were found to respond positively to the therapy, a 15 percent better response than was found with previous methods of treatment.
Scans performed just before surgery were not good indicators of response to the injected treatments. However, the F-18 FDG ET/CT studies from the twelfth day showed a positive correlation with outcomes confirmed at surgery.

“This provides more evidence that early and close monitoring of the patient with PET/CT during the first phase of a patient’s course of treatment can increase the predictive value of the response assessment,” said Luigi Aloj, MD, lead author of the study. “These results could potentially lead to more research for the use of PET/CT to not only predict response to therapy, but to tailor more aggressive treatment for non-responsive patients.”