Surveillance Scanning in Transformed Indolent Lymphoma Is of Limited Clinical Benefit
In patients with transformed indolent lymphoma (TrIL) who achieve a complete metabolic remission, surveillance PET/CT scans are of limited clinical benefit.
In a retrospective analysis of patients with TrIL 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.
The finding builds on prior evidence that surveillance scans after achievement of complete remission in patients with aggressive lymphoma do not lead to improved outcomes, he said.
Fifty-five patients with TrIL treated at Peter MacCallum Cancer Centre, East Melbourne, Australia, who achieved complete metabolic remission after primary therapy and who had subsequent surveillance PET/CT scans, were included in the analysis. During the time the patients in the study were managed, departmental protocol had recommended 6-monthly scans for patients in complete metabolic remission for the first 2 years, then annually until 5 years after completion of therapy, if there was intention to intervene on detection of subclinical relapse.
PET/CT scans and reports were reviewed and classified as either positive, negative, or indeterminate for relapsed lymphoma. True-positive results required either biopsy confirmation or unequivocal scan progression. A false-positive scan was refuted by a negative biopsy or no progression within 6 months. A negative scan was interpreted as negative for relapsed lymphoma: true negatives had no clinical relapse, and false negatives manifest relapse within 3 months from the date of the negative scan.
Of 180 surveillance PET/CT scans, there were 153 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%, sensitivity was 93%, positive predictive value was 54%, and negative predictive value was 99%.
The high negative predictive value is reassuring but comes at a cost of radiation exposure, use of healthcare resources, and unnecessary biopsies, said Cheah, a hematology fellow at Peter MacCallum Cancer Centre.
After a median follow-up of 34 months, the actuarial 3-year progression-free and overall survival were 77% and 88%, respectively. “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,” he 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,” said Cheah.
Sixteen patients experienced disease relapse; 7 were subclinical and 9 were suspected on the basis of clinical symptoms. Although 5% of scans in the first 2 years detected a subclinical relapse, all of these were shown to be low-grade lymphoma either clinically or by biopsy. All diffuse large B-cell lymphoma relapses, in contrast, were accompanied by clinical symptoms.
“Picking up patients that didn’t have symptoms didn’t change management,” he said. “If they didn’t have symptoms, they didn’t warrant treatment anyway.” PET/CT should therefore be reserved for evaluation of suspected relapse only, he said.
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