Prediction of treatment response in subtypes of non-Hodgkin's lymphoma by in vivo 31P MR spectroscopy before treatment

Abstract

8565 Background: To determine if the intracellular tumor marker of phosphoethanolamine plus phosphocholine normalized by nucleotide triphosphates (PPN) monitored non-invasively by phosphorus MR spectroscopy (31P-MRS) correlate with indicators of treatment response in non-Hodgkin's lymphoma (NHL) subtypes. Methods: The PPN value was obtained in 33 diffuse large B-cell lymphomas (DLBCL), 18 follicular lymphomas (FL) and 16 other types (OT) of NHL using in vivo 3D-localized, 1H-irradiated 31P-MRS prior to standard treatment. Results: The PPN values (mean ± standard error) for complete responses (CR) and not complete responses (NCR) in DLBCL were significantly different (CR: 1.42±0.10, n=19 and NCR: 2.25±0.15, n=14; p<0.00002). A Fisher test with a cutoff maximizing PPN sensitivity and specificity (1.78) showed a p<0.004 (sensitivity=0.6, specificity=1.0). Further, when the PPN was combined with the international prognostic index (IPI) to predict treatment response, the Fisher test increased significance (p<0.0002; sensitivity and specificity=0.9). In addition, the two groups dichotomized by the PPN-IPI combination showed a significant difference for drug-free survival (p<0.0001)with one group with survival below 20 months. FL patients did not show PPN significance (CR: 1.40±0.16, n=4 and NCR: 1.75±0.15, n=14). Although this could be due to the lower number of patients, the mean PPN value of the NCR group of FL was significantly lower than that of DLBCL (p<0.01). In the OT group there was only one CR observation but the PPN of its NCR cases was 2.51±0.25, n=13. This value was not significantly different from that of DLBCL but was against that of FL (p<0.007). Conclusions: Our results show that: 1) the pretreatment PPN can predict treatment response in DLBCL identifying a group of DLBCL patients with DFS below 20 months; 2) FL and DLBCL showed distinctive metabolic behaviors; and 3) the number of CR cases was low for FL and OT limiting analysis of PPN until larger cohorts of patients are accrued. No significant financial relationships to disclose.