Baseline PET as prognostic index in diffuse large B-cell lymphoma and grade IIIb follicular lymphoma: a retrospective study of a single-centre experience.

BACKGROUND: International guidelines support performing baseline positron emission tomography (PET) in lymphoma. Metabolic tumor volume (MTV) measurement has been proposed as a good measurement of disease burden. We investigated if MTV at baseline PET can be predictive of complete response (CR) to first line standard chemotherapy in diffuse large B-cell lymphoma (DLBCL) and in follicular lymphoma (FL) grade 3b.

METHODS: We retrospectively analyzed data on54 consecutive patients with DLBCL and FL grade 3b treated in our institution. Dedicated software automatically estimated the SUVmax of the most active lesion and the MTV of the entire lesion burden using an isocontour threshold method set at 42% (MTV42) and 28% (MTV28) of the SUVmax. In addition, the ratio value (MTV28/MTV42) was calculated. Every group of lesion was evaluated separately. All patients were treated with R- CHOP-21. We performed a univariate and a multivariate logistic regression analysis to explore any possible association between PET parameters and CR.

RESULTS: At the univariate logistic regression analysis, patients with a MTV28 lower than the median value (173.1) had an odds ratio (OR) of 4 (95% confidence interval CI 0.94-16.9) of obtaining a CR in comparison to patients with a MTV 28 higher than the median value; patients with a MTV42 lower than the median value (i.e. 85.6) had an OR of 3.63 (95% CI 0.85-15.34) of obtaining a CR in comparison to patients with a MTV 42 equal or higher than the median value. Using MTV28/MTV42 value with median as cut-off instead of MTV28, patients with a MTV28/MTV42 lower than the median value (i.e. 1.81) had an OR of 4.26 (95% CI 0.72-25.07) and of 7.54 (95% CI 0.70-80.91) of obtaining a CR in comparison to patients with a MTV28/MTV42 equal or higher than the median value in the two models, respectively.

CONCLUSIONS: The results of our study suggest that MTV could be a useful tool to predict response to R-CHOP in patients affected with DLBCL and FL grade 3b and that a multi-parameters evaluation should be considered.