Abstract: Follicular Lymphoma (FL) is the most common indolent lymphoma derived from light zone germinal center B cells and characterized by a t(14;18) translocation resulting in upregulation of BCL2 in over 80% of cases. This translocation alone is not sufficient for tumorogenesis, and must be combined with additional genetic mutations to transform B cells. FL is incurable and the disease course can be highly varied, with survival ranging from a few months to decades following diagnosis and treatment with standard chemoimmunotherapy. The heterogeneity of FL poses major challenges to identifying the association of genetic alterations and clinical outcome. Current WHO guidelines recommend establishing grade for each FL case with grade 3 thought to be more aggressive than 1 and 2. The genetic basis and clinical implications of grade in FL are unclear. Recent sequencing studies have identified many genes found to be recurrently mutated in FL including KMT2D and CREBBP. However, the degree to which genetic alterations cooperate with each other or contribute to clinical outcome is unclear. Based on the observed mutational rates in follicular lymphoma, we estimated 900 cases were needed to comprehensively delineate the genetic alterations that underlie histologic grade and clinical outcome. Accordingly, we enrolled a cohort of 1042 patients with newly diagnosed FL. All treated patients received rituximab-containing standard regimens. To go beyond the identification of gene-coding events, we developed a very large panel of 110 Mbp covering exonic (~40Mbp) and non-exonic regions (~70Mbp) of interest to enable a wide range of genomic analysis including mutation calling in both coding and non-coding regions, rearrangement detection, viral identification, and copy number analysis. In addition to the whole exome, we extended coverage to include introns, promoters, and untranslated regions of all known driver genes in cancer. We included the entirety of the immunoglobulin loci, T-cell receptor loci and CD3 loci to detect clonotypes and rearrangements. We also included lymphoma-relevant long non-coding RNAs, microRNAs, enhancers, and breakpoint-prone regions. For viral detection, we targeted the genomes of eight cancer-related viruses: Epstein-Barr virus, human papillomavirus, human immunodeficiency virus, hepatitis B, hepatitis C, Kaposi's sarcoma-associated herpesvirus, human T-lymphotropic virus, and Merkel cell polyomavirus. In addition, to enable high resolution identification of copy number variation (CNV) calls, the entire genome was tiled with probes spaced 10kb apart. DNA and RNA were extracted from all tumors and their paired normal samples, prepared into DNA and RNA sequencing libraries and subjected to sequencing on the Illumina platform to a targeted coverage of 150X. Somatic events were identified and further filtered to identify driver events in both coding and non-coding regions. FLs demonstrated a significant degree of genetic heterogeneity with over 100 genes mutated with a frequency of at least 2%. Nearly 100% of FL cases had a mutation in at least one chromatin-modifying gene. The most frequently mutated genes in follicular lymphoma were KMT2D, BCL2, IGLL5 and CREBBP. In addition, we identified frequent mutations in SPEN, BIRC6 and SETD2. To our knowledge, this is the first description of alterations in these genes in FL. Transcriptome analysis indicated a strong correlation between BIRC6 mutations and the previously described immune response 2 signature that is associated with a poor prognosis. We further performed unbiased clustering of genetic alterations in these FL cases. We identified a cluster that was specifically enriched in BCL6 and TP53 alterations and was strongly associated with grade 3 FLs which are predicted to have poorer outcomes with low intensity therapies. We further examined the genetic profiles of 1001 DLBCLs in comparison to this cohort of FLs. Our data indicate a continuum of highly overlapping genetic alterations with DLBCL displaying more complex patterns that included alterations in MYC, TP53 and CDKN2A (mainly copy number losses), indicating shared pathogenetic mechanisms underlying FL and DLBCL, particularly those germinal center B cell origin. Disclosures Koff: Burroughs Wellcome Fund: Research Funding; V Foundation: Research Funding; Lymphoma Research Foundation: Research Funding; American Association for Cancer Research: Research Funding. Leppä:Roche: Honoraria, Research Funding; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen-Cilag: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees. Gang:ROCHE: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Hsi:Abbvie: Research Funding; Eli Lilly: Research Funding; Cleveland Clinic & Abbvie Biotherapeutics Inc: Patents & Royalties: US8,603,477 B2; Jazz: Consultancy. Flowers:AbbVie: Consultancy, Research Funding; Denovo Biopharma: Consultancy; BeiGene: Consultancy, Research Funding; Burroughs Wellcome Fund: Research Funding; Eastern Cooperative Oncology Group: Research Funding; National Cancer Institute: Research Funding; V Foundation: Research Funding; Optimum Rx: Consultancy; Millenium/Takeda: Research Funding; TG Therapeutics: Research Funding; Gilead: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Karyopharm: Consultancy; AstraZeneca: Consultancy; Pharmacyclics/Janssen: Consultancy, Research Funding; Spectrum: Consultancy; Bayer: Consultancy; Acerta: Research Funding; Genentech, Inc./F. Hoffmann-La Roche Ltd: Consultancy, Research Funding. Neff:Enzyvant: Consultancy; EUSA Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees. Fedoriw:Alexion Pharmaceuticals: Other: Consultant and Speaker. Reddy:Genentech: Research Funding; BMS: Consultancy, Research Funding; Celgene: Consultancy; KITE Pharma: Consultancy; Abbvie: Consultancy. Mason:Sysmex: Honoraria. Behdad:Loxo-Bayer: Membership on an entity's Board of Directors or advisory committees; Thermo Fisher: Membership on an entity's Board of Directors or advisory committees; Pfizer: Other: Speaker. Burton:Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel; Celgene: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Dave:Data Driven Bioscience: Equity Ownership.

Abstract: Follicular lymphoma (FL) is the most common indolent lymphoma. Currently there are many comparable treatment options available for FL. When selecting the most optimal therapy it is important to consider possible late effects of the treatment as well as survival. Secondary haematological malignancy (SHM) is a severe late effect of treatments, but the incidence of SHMs is still largely unknown. The goal of the present study was to determine the incidence of SHMs and how therapeutic decisions interfere with this risk. The study included 1028 FL patients with a median follow‐up time of 5·6 years. The 5‐year risk of SHM was 1·1% and the risk was associated with multiple lines of treatment ( P  = 0·016). The 5‐year risk of SHM was 0·5% after the first‐line treatment and 1·6% after the second‐line. The standardized incidence ratio (SIR) was 6·2 (95% confidence interval 3·4–10·5) for SHM overall. This retrospective study found that the risk of SHM was low after first‐line treatment in FL patients from the rituximab era. However, the risk of SHM increases with multiple lines of treatment. Therapeutic approaches should aim to achieve as long a remission as possible with first‐line treatment, thereby postponing the added risk of SHM.

Abstract: Introduction Follicular lymphoma (FL) is the most common indolent lymphoma. Majority of the patients with FL have a good respond to first-line treatment. Relapses are common and many patients need to be re-treated (Izutsu K. J Clin Exp Hematop 2014). Treatment results of indolent non-Hodgkin lymphomas have improved vastly in last decades. This is resulting from the use of therapeutic antibodies such as rituximab (Friedberg JW. Haematologica 2008). With improved survival the risk of secondary malignancies may be higher. Some of the regimens used in the treatment of FL, especially alkylating agents, have been associated with the risk of secondary hematological malignancies such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Incidence of secondary MDS/AML peaks 4-6 years after the initial treatment. Secondary MDS/AML have poor prognosis. The incidence of secondary hematological malignancies and the impact of various treatment regimens among different lymphomas is still largely unknown (Friedberg JW. Haematologica 2008). Data of 1045 patients with FL was collected to find out the incidence of secondary hematological malignancies. We also wanted to know if the incidence is related to certain types of treatment or chemotherapy regimens. Methods This is a retrospective registry study. Clinical data was collected from six hospitals in Finland and two hospitals in Spain. We analyzed clinical data from hospital records of all patients with FL diagnosed between 1997 and 2016. Information such as age, stage, details of treatment, possible relapses, current status and details about secondary hematological malignancy were investigated. Results Median follow-up time was 5.6 years. Baseline characteristics and treatment-related data are presented in Table 1. Altogether 984 of all patients received treatment for lymphoma and from all patients 80.1% received rituximab during treatment. In all patients the 1-year PFS was 92.1% and the 5-year PFS 59.8%. The 5-year DSS was 91.6% and the 5-year OS was 84.1%. The incidence of secondary hematological malignancies is presented in Figure 1a. From all patients 15 (1.4%) developed secondary hematological malignancy. There were 5 cases of MDS, 4 AML, 1 acute promyelosytic leukemia, 1 acute lymphoblastic leukemia, 1 chronic lymphosytic leukemia, 1 chronic myelosytic leukemia, 1 large granular lymphosytic leukemia and 1 myeloma. The 5-year risk for secondary hematological malignancy was 1.3% and the approximated 10-year risk was 3.0%. The risk of secondary hematological malignancy was associated with the number of treatment lines (p=0.039), Figure 1b. There was no statistically significant difference between different first-line chemotherapy regimens. However, there was a trend presenting higher risk, when using alkylating regimens in the first line. With CHOP-like treatment the 5-year risk was 1.1% and the approximated 10-year risk was 3.6%. Conclusions This is a retrospective study from rituximab era. The prognosis of follicular lymphoma is good with the current treatment methods and the risk of secondary hematological malignancy seems to be low. Due to low incidence, it seems, that it is not necessary to avoid chemotherapy in the fear of secondary hematological malignancies. However, multiple lines of treatment are associated with higher risk for secondary hematological malignancies. Therefore, the use of regimens with long remission, like rituximab maintenance, would probably reduce the risk of secondary hematological malignancies. Disclosures No relevant conflicts of interest to declare.