PET/CT AND EBV VIRAL LOAD IN NASOPHARYNGEAL CARCINOMA

NEW YORK (Reuters Health) Jul 24 - Chinese researchers have developed a more cost-effective way to use positron emission tomography and computed tomography (PET/CT) to detect metastases in patients with nasopharyngeal carcinoma.

The approach, which was published online July 15 in the Journal of Clinical Oncology, is based on Epstein-Barr virus (EBV) DNA levels and N stage.

"The resources of expensive PET/CT are scarce and there is insufficient PET/CT availability for all the nasopharyngeal carcinoma patients," said senior author Dr. Hai-Qiang Mai of Sun Yat-sen University Cancer Center in Guangzhou.

"Targeting the resource to those who will benefit the most, and those in greatest need, should allow us to maximize the care of the population of patients with nasopharyngeal carcinoma," he told Reuters Health by email.

The study included 583 patients with World Health Organization (WHO) type 2 or 3 nasopharyngeal carcinoma treated at the Sun Yat-sen University Cancer Center.

All of the patients underwent PET/CT, magnetic resonance imaging (MRI) of the head and neck and a clinical work-up that included a chest x-ray, abdominal ultrasound and skeletal scintigraphy.

The researchers also measured plasma EBV DNA levels in all patients. Infection with the virus is strongly associated with WHO type 2 and 3 nasopharyngeal carcinoma and has been a tool used for diagnosis, risk stratification, and predicting the prognosis of patients, Dr. Mai said.

Distant metastases were found in 86 (14.8%) of the patients; 71 of these cases were detected by PET/CT and 31 by conventional workup.

On multivariable analysis, advanced N stage (odds ratio, 2.7) and pretreatment EBV DNA levels (OR, 3.3) were significant risk factors for distant metastases.

The researchers divided patients into groups based on their risk of developing distant metastases. The "very low risk" group included 238 patients with stage N0 or N1 disease and EBV DNA levels of less than 4,000 copies/mL. The "low risk" group included 175 patients with stage N0 or N1 disease and EBV levels of at least 4,000 copies/mL as well as patients with stage N2 or N3 disease and EBV levels of less than 4,000 copies/mL. The "intermediate risk" group included 170 with stage N2 or N3 disease and EBV levels of at least 4,000 copies/mL.

The team then compared the ability of PET/CT to detect distant metastases with a clinical work-up alone in each of the three groups.

Among patients in the very low-risk group, both approaches were equally effective (p=0.062). In both the low-risk and intermediate-risk groups, however, PET/CT was more effective than a clinical work-up (p=0.039 and <0 .001="" p="" respectively="">

Using a clinical work-up led to positive predictive values of 50%, 71.4%, and 90.5% in the very low, low and intermediate-risk groups, respectively; PET/CT produced positive predictive values of 63.6%, 85%, and 94%.

In the very low-risk group, 2.9% of patients' treatment plans were altered because of PET/CT results. In the low- and intermediate-risk groups, 6.3% and 16.5% of patients' treatment plans were altered as a result of PET/CT results.

The corresponding costs per true positive case detected by PET/CT among the three groups were $47,458, $14,188 and $5,005.

The researchers conclude that PET/CT "had little impact" on treatment decisions for very low risk patients. They recommend that such patients receive only a clinical workup, whereas low-risk patients could get either a clinical workup or imaging and intermediate -risk patients should have PET/CT.

In an accompanying editorial, Dr. Mark Levine and Dr. Jim Julian of McMaster University in Ontario, Canada, say the Chinese researchers "should be congratulated for their approach to the optimal use of an expensive test in their country."

But, they add, "care must be taken in making any inferences in terms of any economic advantage of restricting PET/CT to high-prevalence strata." The study, they note, is limited because it did not consider all of the downstream costs of each intervention.

Dr. Mai added that the overall results need to be validated in different countries, and in particular that the plasma EBV DNA levels should be validated in different populations of patients.

SOURCE: http://bit.ly/1c2qqHl and http://bit.ly/1c2qqHl

J Clin Oncol 2013.