medwireNews: Surveillance fluorodeoxyglucose positron emission tomography (FDG-PET) delivers a high false-positive rate and has low specificity during follow up in diffuse large cell lymphoma (DLBCL) patients treated with rituximab, a study shows.
The research team, led by Irit Avivi, from the Israel Institute of Technology in Haifa, and colleagues, say: "The extremely low specificity suggests this approach to be unjustified for the routine use in all DLBCL patients in the rituximab era," adding that "strict criteria identifying patients in whom FU [follow-up]-PET is beneficial are required."
Avivi et al retrospectively studied data on newly diagnosed adult DLBCL patients who achieved clinical remission and had at least one surveillance FDG-PET between 2002 and 2010. They included 35 patients who were treated with cyclophosphamide, hydroxydaunorubicin hydrochloride, vincristine, and prednisone (CHOP) alone between 1995 and 2002, and 84 patients who received CHOP plus rituximab (CHOP-R) between 2003 and 2007.
Patients who received CHOP had a longer median follow-up period, a higher median number of follow-up PET scans per patient, and an increased frequency of radiotherapy administration. Over a median follow-up period of 3.4 years, 49% of CHOP-only and 17% of CHOP-R patients relapsed, which represented a significant difference. Interestingly, 78% of relapsed patients initially presented with advanced disease, regardless of treatment group.
The patients underwent a total of 423 follow-up PET scans - 73% following CHOP-R and 27% after CHOP only. Of the scans, 80% were interpreted as negative for relapse, with the remainder positive for relapse, the team notes in the American Journal of Hematology.
Overall, follow-up PET had a sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of 100%, 87%, 88%, 37%, and 100%, respectively, for detecting relapse during clinical remission.
The incidence of false-positive scans was significantly higher in CHOP-R versus CHOP-alone patients, at 77% versus 26%. The specificity and positive predictive value of follow-up PET was significantly lower in CHOP-R patients versus CHOP-alone patients, at 84% versus 94% and 23% versus 74%, respectively. Sensitivity, accuracy, and negative predictive value were similar between the two groups.
Analysis indicated that, overall, 14 follow-up PET studies are required to detect a single relapse event. The number was significantly higher in CHOP-only versus CHOP-R patients, at 22 versus seven.