Quantitative Real-Time PCR of Peripheral Blood t(14;18) Positive Cells Predicts Treatment Response and Long-Term Outcome in Patients with Follicular Lymphoma.
Authors: Zohren Fabian , Bruns Ingmar , Barth Juergen , Pechtel Sabrina , Fenk Roland , Schroeder Thomas , Czibere Akos G. , Maschmeyer Georg , Kofahl-Krause Dorothea , Heil Gerhard , Niederle Norbert , Losem Christoph , Welslau Manfred , Germing Ulrich , Kronenwett Ralf , Haas Rainer , Rummel Mathias J , Kobbe Guido 
Published: October 2019

Abstract
Abstract 441

Introduction:
By means of standard chemotherapy advanced stage follicular lymphoma (FL) is an incurable disease. Clinical courses are characterized by a continuous tendency to relapse caused by residual neoplastic cells. Quantitative polymerase chain reaction (qPCR) to detect lymphoma cell that carry the t(14;18) translocation is a suitable method to measure minimal residual disease (MRD) in patients with FL. Despite several reports dealing with MRD qPCR in FL, its role in the clinical management of patients is still not clearly defined. Therefore, we carried out a multicenter study, to assess the prognostic value of sequential quantitative MRD detection in first-line treatment of FL using an improved version of a LightCycler based qPCR specific for the major breakpoint region (MBR) positive IgH/bcl2 translocation, provided by Roche Diagnostics® (Penzberg Germany).

Patients and Methods:
We analysed 718 blood (PB) samples of 179 patients with newly diagnosed FL treated within the multicenter randomized trial NHL1, conducted by the German StiL group (Study group indolent Lymphomas), comparing 6 cycles of R–CHOP versus R–Bendamustin (R-B). Samples were taken at diagnosis, after 6 cycles of either R–CHOP or R–B immuno-chemotherapy and every three months during follow-up. All samples were analyzed in the department of Hematology at Heinrich-Heine University in Duesseldorf.

Results:
At diagnosis, 112 out of 179 patients (62.6%) were positive for IgH/bcl2 within the MBR in the peripheral blood. Significantly higher amounts of bcl2/IgH positive cells were found in patients with bone marrow infiltration (p=0.012) and depending on the number of lymphatic nodes (LN) with disease involvement (>3 LN p=0.003; >5 LN p=0.0009; >7 LN p=0.022). Overall, a remarkable inter-individual variation of bcl2/IgH positive cells in the PB at diagnosis, reflected by ratios from 0.000281 to 81, was found. The estimated event free survival (EFS) at 2 years of patients who presented at diagnosis low to normal amounts of bcl2/IgH positive cells in the PB (ratio < 2, n=83) was 82% (SE 0.045), which was significantly better than the 47% (SE 0.11) observed in patients showing the highest amount of bcl2/IgH positive cells (ratio >2, n=24) in the PB (p=0.003). By univariate and multivariate analysis, we found that the amount of bcl2/IgH positive cells in the PB at diagnosis (p=0.001) as well as the achievement of a negative MRD status after therapy (p=0.0001) were significant predictors for relapse free survival. Monitoring of MRD levels before and after therapy revealed that 6 cycles of immuno-chemotherapy significantly reduced the amount of bcl2/IgH positive cells in the PB compared with pre-treatment MRD levels (p=0.0001; median bcl2/IgH/tPA ratio: before treatment 0.0734, range: 0.000281–81, after treatment negative, range: negative–0.17). After treatment, 86% of the patients (n=82) achieved a molecular remission in the PB defined as qPCR negative, whereas 14% (13 patients) remained PCR positive. Not reaching a molecular remission in the PB at the end of therapy had a significant negative influence on PFS. After a median follow-up of two years, patients who remained MRD positive in the first measurement after therapy had a significant lower PFS than MRD negative patients (p=0.0001; 9 months vs. not reached). There was no significant difference in the degree of tumor cell depletion in the PB induced by the two different regimens. So far, 539 follow-up samples from 3 up to 39 months after therapy were analyzed. Patients with a consistent negative MRD status throughout follow-up showed a trend towards longer PFS. After 38 months follow-up, MRD positive patients had a PFS of 54% compared to 78% in the group of MRD negative patients (p=0.066).

Conclusion:
QPCR for the t(14;18) performed at diagnosis and during follow-up on PB samples predicts treatment response and long-term clinical outcome of patients with FL.

Disclosures:
Zohren: Roche: Honoraria, Research Funding. Rummel:Roche Pharma AG: Honoraria, Research Funding; Mundipharma: Honoraria, Research Funding; Amgen: Honoraria. Kobbe:Roche: Research Funding.