Kate Johnson

June 10, 2015

BALTIMORE, MD — A follow-up positron emission tomography/computed tomography (PET/CT) scan performed more than 6 months after completion of therapy for non-Hodgkin lymphoma (NHL) is "highly sensitive and specific" for detecting disease recurrence, according to new research reported here at the Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2015 Annual Meeting.

Yet, the National Comprehensive Cancer Network (NCCN) does not recommend doing PET/CT follow-up in patients with NHL, reported the study's lead investigator Mehdi Taghipour, MD, a research fellow from the department of radiology at the Johns Hopkins Medical Institutions in Baltimore, Maryland.

An expert approached for comment was critical of the premise behind this study.

"This study is not only in conflict with the NCCN guidelines, but also the Lugano Classification, and a large body of data," said Bruce Cheson, MD, professor of medicine and head of hematology at the Lombardi Comprehensive Cancer Center, Georgetown University Hospital, Washington, DC. (Dr Cheson was instrumental in developing the Lugano Classification, which outlines "Recommendations for initial evaluation, staging, and response assessment of Hodgkin and non-Hodgkin lymphoma" ( J Clin Oncol. 2014 Sep 20;32:3059-3068).

Dr Cheson told Medscape Medical News: "In 80% of cases, it is the patient or doctor who identifies a relapse and at that time a scan is warranted." He noted that a recent study ( J Clin Oncol. 2014 Nov 1;32:3506-3512) from the Mayo Clinic showed that a surveillance scan identified an asymptomatic recurrence in only 1.8% of patients with diffuse large B-cell NHL, and there was no impact on survival. Moreover, the false-positive rate is high and results in unnecessary additional testing and diagnostic procedures, he said.

"The appropriate practice should be one PET-CT for staging and another 6-8 weeks following chemoimmunotherapy, with no additional studies unless clinically warranted. We should be protecting patients from excessive scanning, rather than encouraging the practice," Dr Cheson said.

Study Details

The study presented at the meeting by Dr Taghipour and colleagues included all patients (n = 204) with NHL who were evaluated with a follow-up PET/CT scan between 2000 and 2013 at his institution.

A total of 560 follow-up scans were included in the study, and their accuracy as well as their impact on patient management was measured.

Among the cohort of 204 patients, 77% survived, with the main treatment being chemotherapy (80.9%), followed by radiotherapy (10.8%).

The sensitivity of scans for predicting recurrence was 95.1%, with a specificity of 90.5%, a positive predictive value of 84.5%, and a negative predictive value of 97.1%, Dr Taghipour reported.

Among the 560 scans, 338 were done without prior clinical suspicion of recurrence, with the remaining 172 done for suspicion of recurrence.

"The follow-up CT scan was helpful in excluding tumor in 17.4% of scans when scans were done with prior clinical suspicion of recurrence. On the other hand, in 22% of scans that were done without clinical suspicion of disease, the follow-up CT detected suspected recurrence," he said.

Treatment information collected both before and after the scans showed that among patients whose scans were performed because of suspicion of recurrence 37.8% had a change of treatment based on scan results (34.3% new treatment, 3% change in treatment, and 0.5% treatment stopped).

Among patients not suspected of having a recurrence, 8.3% had their treatment changed based on the scan results (7.5% new treatment, 0.5% change in treatment, and 0.3% treatment stopped).

Dr Taghipour reported no conflicts of interest.Dr Cheson has disclosed receiving research grants from Celgene, Teva, Pharmacyclics, Gilead, Acerta, Seattle Genetics, MedImmune, Roche-Genentech, and AbbVie, and income in an amount equal to or greater than $250 from Celgene, Teva, Pharmacyclics, Gilead, Seattle Genetics, MedImmune, Roche-Genentech, Pfizer, Spectrum Pharmaceuticals, and Merck.

Society of Nuclear Medicine and Molecular Imaging (SNMMI) 2015 Annual Meeting: Abstract 599. Presented June 9, 2015.

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