New Orleans, LA—In patients with transformed indolent lymphoma (TrIL) who achieve a complete metabolic remission, surveillance scanning with positron emission tomography–computed tomography (PET-CT) is of limited clinical benefit, based on results of a retrospective analysis presented at ASH 2013.
The study included 55 patients with TrIL who were managed at a single institution; “all subclinical relapses were low-grade histology and therefore of limited clinical benefit, as such patients rarely merit further therapy based on imaging findings alone,” said lead investigator Chan Y. Cheah, MD, Peter MacCallum Cancer Centre, East Melbourne, Australia.
This finding builds on previous evidence that surveillance scans after complete remission (CR) in patients with aggressive lymphoma do not lead to improved outcomes, Dr Cheah said.
Patients were included in the analysis if they reached CR after primary therapy and had subsequent surveillance PET-CT. During the study period, the treatment protocol called for 6 scans monthly for patients in CR for the first 2 years, followed by an annual scan for 5 years posttreatment if subclinical relapse was detected.
Of 180 surveillance PET-CT scans, 153 were true negatives, 4 false positives, 1 false negative, 7 indeterminate, and 15 true positives. Considering indeterminate scans as false positives, the specificity of PET-CT for detecting relapse was 93%, the sensitivity was 93%, the positive predictive value was 54%, and the negative predictive value was 99%.
The high negative predictive value is reassuring, but it comes at a cost of radiation exposure, use of healthcare resources, and unnecessary biopsies, said Dr Cheah.
After a median follow-up of 34 months, the actuarial 3-year progression-free survival rate was 77% and overall survival was 88%.
Overall, 16 patients had disease relapse: 7 were subclinical and 9 were suspected on the basis of clinical symptoms. Although 5% of the scans in the first 2 years detected a subclinical relapse, all were shown, clinically or with a biopsy, to be low-grade lymphoma. All diffuse large B-cell lymphoma relapses, in contrast, were accompanied by clinical symptoms.
“We were unable to find any prognostic factors besides age older than 60 years to isolate a subset of particular patients in whom a surveillance strategy could be focused,” Dr Cheah said. “When patients relapsed with large-cell disease, they typically presented with symptoms first. If they relapsed with indolent disease, they didn’t necessarily have symptoms,” he said.
“Picking up patients that didn’t have symptoms didn’t change management,” Dr Cheah said. “If they didn’t have symptoms, they didn’t warrant treatment anyway.” PET-CT should therefore be reserved for the evaluation of suspected relapse only, he advised.