Minimal residual disease (MRD) analysis is a known predictive tool in mantle cell lymphoma (MCL). We describe MRD results from the Fondazione Italiana Linfomi phase III MCL0208 prospective clinical trial assessing lenalidomide maintenance vs observation after autologous transplantation (ASCT), in the first prospective comprehensive analysis of different techniques, molecular markers, and tissues (peripheral blood, PB, and bone marrow, BM), taken at well-defined timepoints. Among the 300 patients enrolled, a molecular marker was identified in 250 (83%), allowing us to analyze 234 patients and 4351 analytical findings from 10 timepoints. ASCT induced high rates of molecular remission (91% in PB and 83% in BM, by quantitative real-time PCR [RQ-PCR]). Nevertheless, the number of patients with persistent clinical and molecular remission decreased over time in both arms (up to 30% after 36 months). MRD predicted early progression and long-term outcome, particularly from 6 months after ASCT (6-month TTP HR 3.83, p<0.001). In single-timepoint analysis, BM outperformed PB, and RQ-PCR was more reliable, while nested PCR appeared applicable to a larger number of patients (234 vs 176). To improve MRD performance we developed a time-varying kinetic model, based on regularly updated MRD results and the Mantle Cell Lymphoma International Prognostic Index, showing an area under the ROC curve (AUROC) of up to 0.87 using BM. Most notably, PB reached an AUROC of up to 0.81: with kinetic analysis it was comparable to BM in performance. MRD is a powerful predictor over the entire natural history of MCL and suitable for models with continuous adaptation of patient risk. Study can be found in EudraCT N. 2009-012807-25 https://eudract.ema.europa.eu/

In IgM monoclonal gammopathies MYD88L265P is a prognostic and predictive biomarker of therapy response. MYD88L265P detection is mainly performed by allele-specific quantitative PCR (ASqPCR), however recently, droplet digital PCR (ddPCR) has been proved to be suitable for MYD88L265P screening and minimal residual disease monitoring (MRD). This study compared ASqPCR and ddPCR to define the most sensitive method for MYD88L265P detection in bone marrow (BM), peripheral blood (PB) sorted or unsorted CD19+ cells, and in plasma cell-free DNA (cfDNA). Overall, the analysis showed a good concordance rate (74%) between the two methods, especially in BM samples, while discordances (26%) were mostly in favor of ddPCR (ddPCR+ vs. ASqPCR-) and were particularly evident in samples with low mutational burden, such as PB and cfDNA. This study highlights ddPCR as a feasible approach for MYD88L265P detection across different specimen types (including cfDNA). Interestingly, its high sensitivity makes CD19+ selection dispensable. On the other hand, our results showed that MYD88L265P detection on PB samples, especially with ASqPCR, is suboptimal for screening and MRD analysis. Finally, significantly different MYD88L265P mutational levels observed between Waldenström Macroglobulinemia and IgM monoclonal gammopathy of undetermined significance patients suggest the need for further studies in order to identify possible correlations between mutational levels and risk of progression to Waldenström.

Based on promising results in preclinical models, clinical trials have been performed to evaluate the efficacy of the first-in-class proteasome inhibitor bortezomib towards malignant pleural mesothelioma (MPM), an aggressive cancer arising from the mesothelium of the serous cavities following exposure to asbestos. Unexpectedly, only minimal therapeutic benefits were observed, thus implicating that MPM harbors inherent resistance mechanisms. Identifying the molecular bases of this primary resistance is crucial to develop novel pharmacologic strategies aimed at increasing the vulnerability of MPM to bortezomib. Therefore, we assessed a panel of four human MPM lines with different sensitivity to bortezomib, for functional proteasome activity and levels of free and polymerized ubiquitin. We found that highly sensitive MPM lines display lower proteasome activity than more bortezomib-resistant clones, suggesting that reduced proteasomal capacity might contribute to the intrinsic susceptibility of mesothelioma cells to proteasome inhibitors-induced apoptosis. Moreover, MPM equipped with fewer active proteasomes accumulated polyubiquitinated proteins, at the expense of free ubiquitin, a condition known as proteasome stress, which lowers the cellular apoptotic threshold and sensitizes mesothelioma cells to bortezomib-induced toxicity as shown herein. Taken together, our data suggest that an unfavorable load-versus-capacity balance represents a critical determinant of primary apoptotic sensitivity to bortezomib in MPM.

Minimal residual disease (MRD) determined by classic polymerase chain reaction (PCR) methods is a powerful outcome predictor in mantle cell lymphoma (MCL). Nevertheless, some technical pitfalls can reduce the rate of of molecular markers. Therefore, we applied the EuroClonality-NGS IGH (next-generation sequencing immunoglobulin heavy chain) method (previously published in acute lymphoblastic leukaemia) to 20 MCL patients enrolled in an Italian phase III trial sponsored by Fondazione Italiana Linfomi. Results from this preliminary investigation show that EuroClonality-NGS IGH method is feasible in the MCL context, detecting a molecular IGH target in 19/20 investigated cases, allowing MRD monitoring also in those patients lacking a molecular marker for classical screening approaches.

Background. Immunochemotherapy is effective in follicular lymphoma (FL), but most patients (pts) eventually relapse. MRD analysis, based on the detection of Bcl-2/IGH rearrangement by highly sensitive PCR-based tools, is effective in identifying pts at risk of relapse [Ladetto Blood 2012; Pott EHA23]. However, several issues are still unresolved, including: i) which is the best tissue source and the most reliable technique; ii) which are the most predictive time points; iii) which is the role of disease kinetics during the long natural history of FL. The FIL FOLL12 prospective, phase III randomized clinical trial (EudraCT: 2012-003170-60) included a systematic MRD analysis on both peripheral blood (PB) and bone marrow (BM) taken at eight different pre-planned time points, by both nested and real time quantitative (RQ)-PCR. Therefore, it allows addressing these unresolved issues. Methods. The FOLL12 compared conventional rituximab maintenance [Salles et al, Lancet 2010] vs a combined PET/MRD response-based post-induction approach in pts with advanced FL after first line chemo-immunotherapy. Clinical results have been already reported [Luminari et al, ICML16]. PB and BM samples were centralized at four Italian Euro-MRD certified laboratories. MRD was assessed with consensus primers on Bcl-2/IGH rearrangements (MBR, mcr and minor rearrangements) by both nested and RQ-PCR at eight time points: baseline, end of induction (EoI) and every six months thereafter till month 36. MRD data were treated as a time-varying covariate and analyzed by means of flexible parametric survival model (Parmar-Royston) with the log cumulative baseline hazard function. MRD data were modeled with restricted cubic spline as function of time. Effect of fixed covariates and landmark analysis were performed with the Cox PH regression. Any estimation was reported with its 95%CI. Results. Overall, 10,702 analytical results were generated, (3,000 for marker screening and 7,702 for MRD). 780 of 786 eligible pts (99%) were screened at baseline for the presence of a molecular marker. 443/780 (57%) had a detectable Bcl-2/IGH rearrangement, as expected. High rates of MRD negativity were observed at EoI, with similar results by both techniques (87% in BM and 95% in PB by nested-PCR, 90% in BM and 95% in PB with RQ-PCR). Overall, the presence of one MRD positive result was associated during the entire follow-up period with an increased risk of relapse in the subsequent six months interval (HR for PFS 2.82, 95% CI 1.84-4.34, p<0.001), independently from randomization arm (heterogenous test for HR in PFS 0.330), treatment received (HR 0.859) and FLIPI-2 (HR 0.302). Most notably, a sharp increase of HR was observed during follow-up, with time points after 6 and particularly after 12 months or later outperforming the earliest evaluation. Interestingly, very similar results were recorded in BM or PB and using nested or RQ-PCR (Figure 1A). Despite inferior performance compared to later timepoints, MRD positivity in BM at EoI was nevertheless predictive of a shorter 4y-PFS (61% vs 75% by nested-PCR and 54% vs 74% by RQ-PCR, p=0.03 and p=0.003, respectively). Moreover, a kinetic analysis showed that pts scoring MRD+ at EoI but converting to MRD- in the following time points showed superimposable outcome to pts persistently MRD- (HR for PFS 0.66, 95% CI 0.24-1.82, p=0.420), while pts scoring MRD- at EoI but then converting to MRD+ showed a worse outcome (HR for PFS 1.75, 95% CI 1.21-2.53, p=0.003) (Figure 1B). Actually, Kaplan Meier landmark analyses stratified by updated MRD results at each punctual timepoint after EoI were overall highly discriminant in terms of PFS, with PB results (Figure 1C) substantially overlapping BM performances from months 12 after EoI (not shown) and thereafter. Conclusions. This comprehensive MRD study in FL clearly indicates that: i) punctual MRD analysis is predictive of poor outcome at multiple pre-planned time points taken over a 36 months period; ii) both nested and RQ-PCR performed adequately, the latter being preferable as broadly used and internationally standardized; iii) BM allows better prediction at the early time points but, starting from month 12 after EoI PB is superimposable to BM, allowing effective and reliable long-term non-invasive MRD monitoring; iv) the high predictive value of punctual time point analysis is further improved by a kinetic approach to the interpretation of MRD results. Figure 1 Figure 1. Disclosures Ladetto: AbbVie, Jazz, Gentili, Incyte, ADC Therapeutics, Acerta, Pfizer: Honoraria; Roche, J&J, Celgene, Novartis, Amgen, Gilead, Beigene, GSK: Honoraria. Ferrero: Servier: Speakers Bureau; EUSA Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Morphosys: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees; Gilead: Research Funding, Speakers Bureau; Clinigen: Membership on an entity's Board of Directors or advisory committees. Del Giudice: Tolero: Membership on an entity's Board of Directors or advisory committees; Astrazeneca: Membership on an entity's Board of Directors or advisory committees. Galimberti: Incyte: Speakers Bureau; AbbVie, Janssen: Honoraria, Other: Travel grants. Gattei: abbVie: Research Funding; Janssen: Research Funding; Menarini: Research Funding. Mannina: Janssen,Takeda: Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees. Falini: Rasna Therapeutics: Honoraria. Luminari: Roche, Celgene, Teva Pharmaceuticals, Gilead Sciences, and Takeda Pharmaceuticals: Honoraria.