Impact of Double- or Triple-Hit Pathology on Rates and Durability of Radiation Therapy Response Among Patients With Relapsed or Refractory Large B-Cell Lymphoma

Journal Pre-proof Impact of double/triple hit pathology on rates and durability of RT response among patients with relapsed/refractory large B-cell lymphoma Aileen Kim, MD, Philip Stevenson, MS, Ryan D. Cassaday, MD, Lori Soma, MD, Jonathan R. Fromm, MD PhD, Ajay Gopal, MD, Stephen D. Smith, MD, Brian Till, MD, Ryan Lynch, MD, Chaitra Ujjani, MD, Mazyar Shadman, MD, Edus H. Warren, MD PhD, Manoj Menon, MD MPH, Kenneth Russell, MD, Yolanda D. Tseng, MD MPhil PII:

S1879-8500(19)30277-2

DOI:

https://doi.org/10.1016/j.prro.2019.09.013

Reference:

PRRO 1131

To appear in:

Practical Radiation Oncology

Received Date: 8 August 2019 Revised Date:

12 September 2019

Accepted Date: 24 September 2019

Please cite this article as: Kim A, Stevenson P, Cassaday RD, Soma L, Fromm JR, Gopal A, Smith SD, Till B, Lynch R, Ujjani C, Shadman M, Warren EH, Menon M, Russell K, Tseng YD, Impact of double/ triple hit pathology on rates and durability of RT response among patients with relapsed/refractory large B-cell lymphoma, Practical Radiation Oncology (2019), doi: https://doi.org/10.1016/j.prro.2019.09.013. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.

Impact of double/triple hit pathology on rates and durability of RT response among patients with relapsed/refractory large B-cell lymphoma Aileen Kim MD1, Philip Stevenson MS4, Ryan D. Cassaday MD2,4, Lori Soma MD3, Jonathan R. Fromm MD PhD3, Ajay Gopal MD2,4, Stephen D. Smith MD2,4, Brian Till MD2,4, Ryan Lynch MD2,4, Chaitra Ujjani MD2,4, Mazyar Shadman MD2,4, Edus H. Warren MD PhD2,4, Manoj Menon MD MPH2,4, Kenneth Russell MD1, and Yolanda D Tseng MD MPhil1 1

Department of Radiation Oncology, 2Department of Medicine, and 3Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA; 4Fred Hutchinson Cancer Research Center, Seattle, WA.

Corresponding author contact information: Yolanda D. Tseng, MD Assistant Professor Department of Radiation Oncology University of Washington Medical Center 1959 NE Pacific St, Box 356043 Seattle, WA 98195 E-mail: [email protected] Presented in part at the annual meeting of American Society for Radiation Oncology, Oct 21 24, 2018, San Antonio, TX. Running head: Impact of DHL/THL on RT efficacy Funding/Financial support: None Conflict of interest: None Acknowledgements: This work was supported by database efforts of Seattle Translational Tumor Research (STTR).

Impact of double/triple hit pathology on rates and durability of RT response among patients with relapsed/refractory large B-cell lymphoma

Running head: Impact of DHL/THL on RT efficacy

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Abstract Purpose: Double/triple-hit lymphomas (DHL/THL), also known as high-grade B-cell lymphoma with MYC and BCL2 and/or BCL6 rearrangements, are associated with chemoresistance and inferior survival. However, whether RT efficacy is altered in DHL/THL is less well characterized. Among patients with relapsed/refractory (R/R) large B-cell lymphoma (LCBL), we compared rates and durability of response between patients with and without DHL/THL.

Methods and Materials: We retrospectively reviewed consecutive R/R LBCL patients that were irradiated at a single institution from 1/2008-6/2017. Patients in whom c-MYC rearranged status was known were evaluated for response to RT, in-field control, progression-free (PFS) and overall survival (OS).

Results: Among 245 irradiated patients with LBCL, 41 patients with confirmed c-MYC status were treated for R/R disease (14 DHL/THL, 27 non-DHL/THL) and formed our cohort. Compared to non-DHL/THL, more DHL/THL patients had progressive disease at RT (71% vs 48%), had larger gross tumor volumes (GTV; median 696 mL vs 117 mL), and were treated with palliative intent (71% vs 41%). Despite similar RT doses (median 35 Gy), radiographic complete response rate was lower among DHL/THL patients: 14.3% vs 64.7% (p=0.01). With a median 2 years of follow-up, one in-field failure was observed in each group. DHL/THL patients had inferior PFS (7% vs 46%; p=0.02) and OS (14% vs 68%; p=0.03) at 6 months.

Conclusions: R/R LBCL is responsive to RT, although RR are lower among DHL/THL patients. Given poor survival after RT, in-field control was hard to evaluate in this cohort. Larger cohorts are required to better elucidate whether differences in response rates are driven by larger disease

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burden at RT versus tumor biology. These findings are of increasing pertinence in light of use of RT as bridging therapy to cellular immunotherapies.

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Introduction Approximately 20-50% of patients with large B cell lymphomas (LBCLs) will experience relapsed and/or refractory (R/R) disease, which is associated with poor prognosis.1-3 Despite aggressive salvage systemic therapies, only 15-50% achieve durable remission.4 5 Radiotherapy (RT) represents another treatment option for patients with R/R LBCL, either as consolidation, salvage, or palliation.6 7 LBCL represents a heterogeneous disease entity 8 9, in which patients with translocation of c-MYC, with BCL2, and/or BCL6 have inferior prognosis and present with higher risk disease. 10-12

The updated WHO 2016 classification has recognized these pathologic and clinical findings

in their designation of high grade B-cell lymphoma (HGBCL) with rearrangements of c-MYC, with BCL2, and/or BCL6, also referred to colloquially as double/triple hit lymphomas (DHL/THL).13 DHL/THL are more chemoresistant to conventional induction immunechemotherapies,14-16 which may in part be overcome with intensification of systemic therapy.17 18 In contrast, little is known regarding RT efficacy among patients with R/R DHL/THL. Retrospective data suggest lower rates of local control with RT among patients with chemoresistant lymphoma.7 19-23 We hypothesize that given high rates of chemoresistance associated with DHL/THL, rates and durability of RT response would be lower among R/R patients with DHL/THL compared to non-DHL/THL. Better characterizing the efficacy of RT among R/R DHL/THL patients may help inform whether RT treatment should be intensified, as in the case with chemotherapy.

Methods and Materials Patient cohort

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After obtaining institutional review board approval from XXX institutional review board, we retrospectively reviewed the records of 245 consecutive patients with LBCL that received external beam RT at XXX and XXX from 1/1/2008 to 6/1/2017. Eligible patients were ≥ 18 years of age, received RT in the R/R setting, and whose pathology was evaluated for presence of c-MYC gene rearrangement by fluorescence in-situ hybridization (FISH).13 24 If c-MYC gene rearrangement was detected, BCL-2 and BCL-6 were reflexively tested. Relapsed disease was defined as development of new disease after achieving complete response (CR), while refractory disease was defined as achieving less than a PR to systemic treatment prior to RT. Both de novo and transformed LBCL were included. We excluded patients in whom cMYC gene rearrangement was not tested (n=164), RT was delivered as consolidation after induction chemotherapy (n=32), and RT was directed to the CNS (i.e. primary or secondary CNS lymphoma) (n=8). The remaining 41 patients that received RT in the R/R setting comprised our cohort for analysis. We extracted demographic, pathologic, pre-RT treatment, and RT factors that could influence RT response, in-field control, and progression-free survival (PFS). Patients were considered to have primary chemorefractory disease if they achieved less than a PR to induction chemotherapy. Patients without c-MYC re-arrangements but with increased expression of c-MYC and BCL-2 were categorized as non-DHL/THL. Cell of origin (COO) was defined according to the Hans criteria.9

RT treatment RT intent was categorized as palliative versus curative by the treating radiation oncologist at the time of treatment planning. Based on extent of disease irradiated, RT was

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categorized as consolidation (microscopic disease) versus salvage (gross disease). Given various dose/fractionation schemes that were used, the biological effective dose (BED) was calculated using an alpha/beta ratio of 10. Among patients who received more than one course of RT, only the first course was included in this analysis.

Assessment of response, disease recurrence/progression, and death Response within the RT portal was categorized using the revised response criteria for malignant lymphoma,25 but adapted to the irradiated site (versus systemic treatment response). Use of CT versus of PET/CT imaging prior to RT was at the discretion of the medical oncologist. The timing of imaging prior to RT was also variable given the retrospective nature of this study. Among 38 (93%) of patients with residual disease (i.e. partial response, stable disease, progressive disease) at the time of radiotherapy, 31 (82%) underwent radiographic response assessment after radiotherapy. When both CT and PET/CT imaging studies were available after RT, response was determined based on PET/CT. Response assessment was ascertained based on clinical response in the remaining 7 patients. In addition, among patients with symptoms prior to radiotherapy, we evaluated whether there was clinical improvement of symptoms during radiotherapy, regardless whether imaging was performed. While follow up was not standardized, surviving patients were generally followed every 3-6 months. Patients that achieved a CR, partial response (PR), or stable disease (SD) to RT were analyzed for in-field control, defined as lack of disease progression within the RT portal. Progression outside the irradiated portal was categorized as an out of field-relapse. The date of death was obtained from medical records or XXX State Archives26. Acute (≤ 3 months from RT completion) RT-associated side effects were graded as per CTCAE version 4.

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Statistical analysis The primary endpoints were radiation response and in-field control. Secondary endpoints included PFS and OS, which were measured from date of RT start. For PFS analysis, patients were censored at the last date of disease assessment if they were alive without recurrence or if they died without documented recurrence. Logistic univariate and multivariate models were used to evaluate for predictors of achieving a radiographic CR to RT among patients with gross disease prior to RT. The following variables were assessed for the univariate analysis: COO, primary chemorefractory disease, number of lines of immunochemotherapy prior to RT, relapse versus refractory disease, curative versus palliative treatment intent, consolidative versus salvage RT, gross tumor volume (GTV), RT dose, and BED10. Given the limited number of events, we included only the most clinically significant variables in the multivariate model: GTV, disease status prior to RT (CR vs non-CR), and DHL/THL status. In-field control, PFS, and OS rates at 6 months and 12 months were estimated using the Kaplan-Meier method. Statistical computations were calculated using R (version 3.4.1).

Results Patient, disease, and treatment characteristics Among 41 patients with R/R LBCL, 14 patients had DHL/THL (Table 1). BCL-2 and BCL-6 rearrangements were detected in 13 and 3 patients, respectively. Ten patients had DHL, 2 patients had at least DHL (i.e. confirmed BCL-2 rearrangement and unknown BCL-6 status), and 2 patients had THL.

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Most (70%) patients were male. Compared to non-DHL/THL patients, a higher proportion of DHL/THL patients presented with advanced disease at diagnosis and had transformed disease. Consistent with prior reports27 28, all DHL/THL patients with known COO had germinal center B-cell COO. While more DHL/THL patients received intensified induction immunochemotherapy (Rhyper-CVAD, dose-adjusted EPOCH-R) compared with non-DHL/THL patients (Table 2), responses to induction treatments were similar between the two groups, with most (63%) patients having primary chemorefractory disease. R/R LBCL patients were heavily pre-treated and underwent a median 2 lines of immunochemotherapy prior to RT. Nearly half of the cohort underwent a stem cell transplant, half of which was delivered prior to RT. Among the 16 patients that underwent transplant, 11 received RT within 3 months of transplant (i.e. peri-transplant setting) given the presence of gross disease. Most (7 out of 11) underwent RT prior to transplant for cytoreduction (median 32 days, range 15-60). The remaining four patients underwent RT after autologous stem cell transplant (median 44 days, range 33-56) despite having gross disease prior to transplant. Two of these 4 patients were planned for a tandem autologous and then allogeneic stem cell transplant, and RT was given after the autologous stem cell transplant.

Radiotherapy for R/R disease RT for R/R disease was delivered a median of 9.0 months from diagnosis for DHL/THL patients and 11.5 months for non-DHL/THL patients (Table 3). At the time of RT, more DHL/THL patients presented with refractory disease compared to non-DHL/THL patients and had larger volumes of gross disease irradiated. More DHL/THL patients were irradiated with palliative intent, and all DHL/THL patients were irradiated to gross disease. Despite differences

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in treatment intent and size of disease irradiated, RT dose and BED10 was similar between the two groups. A variety of dose/fractionation schemes were used ranging from 4 Gy in 1 fraction to 50.4 Gy in 28 fractions without a singular dose/fractionation used more than others.

Response to RT and in-field control Median follow-up was 25.3 and 20.5 months for surviving DHL/THL and non-DHL/THL patients, respectively. Among 30 patients with recorded symptoms prior to RT, 71.4% DHL/THL and 51.9% non-DHL/THL had improvement of symptoms during RT (Table 3). Among the 31 patients with radiographic assessment for residual disease after radiotherapy (Table 4), a higher proportion of non-DHL/THL patients achieved a CR to RT compared to DHL/THL patients (64.7% vs. 14.3%; p=0.01). One patient from each group developed in-field progression: a patient with non-DHL/THL received RT to a GTV of the neck measuring 9 mL, which progressed during RT, and therefore dose was escalated from the planned 45 Gy to 57 Gy. While the disease initially responded, it recurred about 3 months after RT completion. Despite multiple salvage treatments, the patient progressed locally and systemically and passed away. The second patient had stage IV DHL, which was treated with dose-adjusted-EPOCH-R, RICE, and RT (45 Gy in 25 fractions) for progressive mesenteric disease. Post-RT PET/CT demonstrated persistent FDG uptake with enlargement of the mass, and the patient underwent CAR T cell and nivolumab. His treatment course was complicated by duodeno-uretero-enteric fistulas, and no further lymphoma-directed treatments were delivered over the subsequent 2.5 years. He remains without disease progression despite persistent FDG-uptake on his last scan, raising consideration whether the FDG-uptake represents an inflammatory process (e.g. appendicitis and/or fistula) versus persistent lymphoma.

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Among patients with residual disease prior to radiotherapy and with radiographic assessment after radiotherapy, we evaluated for predictors of CR to RT in the R/R setting. On univariate analysis, DHL/THL status was associated with achieving a less than a CR with RT (OR 0.09, p<0.01), even after controlling for either volume of gross disease irradiated (adjusted OR 0.05; p<0.01) or RT dose (adjusted OR 0.08, p<0.01). While disease status prior to RT also predicted RT responses on univariate analysis (where PR before RT were more likely to achieve CR to RT compare to SD or PD; p=0.014), DHL/THL status was still associated with achieving non-CR to RT controlling for disease status prior to RT (adjusted OR 0.12; p<0.03).

Progression-free and overall survival R/R DHL/THL patients had significantly higher rates of relapses outside the field (p<0.01) and lower PFS (median 1.1 versus 2.4 months; p=0.015) after RT compared to nonDHL/THL patients (Figure 1). Even among this poor prognosis cohort with R/R disease, DHL/THL patients had significantly worse OS (p=0.03): median 1.9 months versus 11.7 months. Despite such poor prognosis, there were two long-term survivors in DHL/THL group. The first survivor is aforementioned DHL patient who underwent CAR T and nivolumab for locally persistent mesenteric mass after RT, who has been clinically without evidence of disease over the subsequent 2.5 years. The second patient, who presented with stage II THL, achieved a PR to dose-adjusted-EPOCH-R and underwent salvage CAR T, RICE, and allogeneic stem cell transplant prior to RT. He received 41.4 Gy in 23 fractions to persistent mesenteric disease posttransplant. Follow-up imaging demonstrated persistent, but stable FDG-uptake within the irradiated mass, and he remains disease free nearly 3.5 years from RT.

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Adverse events from radiotherapy RT was well tolerated with most patients completing RT as planned (92.7%). Acute grade 3 toxicity was more commonly observed among DHL/THL patients compared with to nonDHL/THL patients: 21.4% vs. 3.7%. The most common grade 3 toxicities were dermatitis, nausea, and hematologic events. One patient with DHL/THL experienced tumor lysis syndrome (grade 4) while being irradiated for a large pelvic mass (GTV 1,095 mL). Late toxicity was difficult to assess given that one-third of patients had either died or had no follow-up 3 months after RT completion. One patient with non-DHL/THL developed a myelodysplastic syndrome.

Discussion Our study confirms that R/R LBCL patients undergoing RT have a poor prognosis, though our cohort may have been enriched with patients undergoing radiotherapy with palliative rather than curative intent. As such, not all sites of disease were necessarily treated and may have contributed to the high out-of-field relapses and low OS observed, especially among patients with DHL/THL. Nonetheless, this is consistent with prior studies, which have shown up to 70% out-of-field relapses and OS around 20% at 1 year.1 20 23 Despite high rates of chemorefractory disease after multiple lines of salvage therapies, R/R LBCL patients were generally radiosensitive with overall response rates of 55% and only two in-field progressions. This was also similar in regard to symptom improvement. While the high observed in-field control rates may reflect the radiosensitivity of R/R LBCL, this must be interpreted in the context of a high competing risk of relapse out-of-field and subsequent mortality. Our findings are timely given the recent FDA-approval of CD19 CAR-T cell therapy for patients with R/R LBCL 29 30. Given that product manufacturing can take several weeks, the high response rates from RT make it an

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attractive, bridging therapy for patients that have disease progression or large tumor burden while awaiting CAR-T cell production. Decreased RT efficacy has been observed in chemorefractory disease, with up to 30-50% of local failures compared to 5-30% in non-chemorefractory disease 19-21 23. Rates of primary chemorefractory disease was similar among DHL/THL and non-DHL/THL patients. Despite this, differences in RT responses were observed among R/R LBCL among patients with gross disease prior to RT, with CR rates of 14.3% in DHL/THL patients versus 64.7% in non-DHL/THL group. After accounting for clinical and pathologic factors that could influence radio-responsiveness, such as the volume of disease treated, radiation doses, and disease status prior to RT, DHL/THL status was associated with achieving less than CR to RT. To our knowledge, this is the first study assessing whether RT efficacy in the R/R setting is altered by DHL/THL status. Despite the chemorefractory nature of DHL/THL, recent retrospective studies31 32 have shown improved locoregional control in patients with DHL/THL that underwent consolidative RT after induction immunochemotherapy, compared to patients that received chemotherapy alone. These studies suggest efficacy of RT in those patients with chemosensitive disease. Response to RT was blunted among patients with R/R DHL/THL, which may reflect altered cellular responses to ionizing radiation (IR). Preclinical models have shown that while c-MYC alteration in mouse embryo fibroblast and precancerous B-cells are more sensitive to IR induced apoptosis33, over-expression of BCL-2 in the presence of c-MYC activation suppressed IRinduced apoptosis34. IR sensitivity in the setting of BCL-6 rearrangement or overexpression is unknown. Therefore, diminished in-field response to RT in DHL/THL may be driven by increased radio-resistance from BCL-2 rearrangement and subsequent anti-apoptotic activities. While our results require confirmation in other cohorts, our findings suggest a need to improve

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distant control in these irradiated patients. This may reflect the large proportion of patients in our cohort that were irradiated with palliative intent due to other disease that was not being radiated and/or clinical assessment that the patient was at high risk of distant relapse. In curative settings, there may be a potential role of intensifying RT among DHL/THL patients given the lower rates of CR to non-DHL/THL patients. Potential strategies include radiation dose escalation, altered fractionation, and/or concurrent systemic therapies, although effectiveness of treatment intensification was not evaluated in our analysis. This study was limited by a retrospective study design. Because DHL/THL is a relatively recently recognized entity, FISH evaluation of c-MYC status was not uniformly evaluated at our institution until 2014. Prior to this, it was performed only in patients who exhibited unusually high chemorefractoriness. Therefore, our study cohort, which required c-MYC status confirmation, may consist of more chemorefractory patients compared to historic R/R LBCL patients. Our study was also limited by small number of patients, which is expected given that DHL/THL consists only 5-10% of LBCL.35 In addition, R/R LBCL patients who were referred for RT were heterogeneous with respect to clinical, pathologic, and treatment characteristics. We were limited by the number of events to adjust for other potentially confounding factors that could influence RT response. Up to 55% of certain key clinical and/or pathologic data (ECOG, LDH, IPI) were missing at initial diagnosis of LBCL. However, among clinical co-variates that were felt to most influence probability of RT response, data was overall complete. Lastly, most patients were followed by hematologic oncologists rather than radiation oncologists. While surveillance after RT focused on disease status systemically rather than locally, we were able to capture local treatment responses for most surviving patients.

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Conclusion While our study findings require confirmation in larger study cohorts, DHL/THL appears to be associated with lower rates of RT response. Despite this, most symptomatic patients, including those with DHL/THL noted symptomatic improvement during RT, highlighting the palliative benefit of RT and potential use of RT as a bridge for cellular immunotherapies. These findings highlight the consideration of RT intensification and/or the unmet need for novel therapies for DHL/THL.

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Figure Legends Figure 1: Kaplan-Meier estimates of (a) progression free survival, and (b) overall survival among DHL/THL and non-DHL/THL patients

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Table 1. Patient demographics and disease characteristics at initial diagnosis † Non-DHL/THL DHL/THL Total Characteristics (N = 27) (N=14) (N=41) Mean age, years (sd) 56.25 (12.25) 59.91 (11.15) 57.57 (11.85) Male (%) 18 (66.7) 11 (78.6) 29 (70.7) Stage (%) I 3 (11.1) 0 (0.0) 3 (7.3) II 5 (18.5) 3 (21.4) 8 (19.5) III 6 (22.2) 2 (14.3) 8 (19.5) IV 9 (33.3) 6 (42.9) 15 (36.6) Unknown 4 (14.8) 3 (21.4) 7 (17.1) Extranodal disease (%) 13 (48.1) 11 (78.6) 24 (58.5) Skeletal involvement (%) 9 (33.3) 4 (28.6) 13 (31.7) B-symptoms (%) Present 8 (29.6) 8 (57.1) 16 (39.0) Absent 11 (40.7) 3 (21.4) 14 (34.1) Unknown 8 (29.6) 3 (21.4) 11 (26.8) De novo vs. transformed (%) De novo 20 (74.1) 8 (57.1) 28 (68.3) Transformed 6 (22.2) 5 (35.7) 11 (26.8) Unknown 1 (3.7) 1 (7.1) 2 (4.9) Mean Ki-67 (SD) 78.56 (14.75) 82.50 (10.00) 79.77 (13.39) Cell-of-origin (%)* Germinal center B cell-like 13 (48.1) 12 (85.7) 25 (61.0) Activated B cell-like 6 (22.2) 0 (0.0) 6 (14.6) Unknown 8 (29.6) 2 (14.3) 10 (24.4) Bulky site (≥ 7.5cm largest diameter) Absent 12 (44.4) 2 (14.3) 14 (34.1) Present 12 (44.4) 12 (85.7) 24 (58.5) Unknown 3 (11.1) 0 (0.0) 3 (7.3) * Based on Han’s criteria18.

† Factors with significant proportion (greater than 40%) of missing records were not presented, including LDH levels, initial ECOG status, and IPI.

Table 2. Induction and salvage therapies

Induction immuno-chemotherapy types: R-CHOP R-Hyper CVAD, DA-EPOCH-R Other (R, Ibrutinib, R-CVP-> R) Induction chemotherapy cycles (median and range) Response to induction chemotherapy: CR PR SD PD Unknown Median number of lines of immunochemotherapy used prior to RT (Range) First line salvage therapy types: Rituximab ICE DHAP GCP Other † Stem cell transplant (%) Autologous Allogeneic Stem cell transplant prior to RT (%) More than one transplant (%)

Non-DHL/THL (N = 27)

DHL/THL (N=14)

Total (N=41)

17 7

6 8*

23 15

3

1

4

6 (2-8)

6 (1-7)

6 (1-8)

4 (14.8%) 6 (22.2%) 7 (25.9%) 10 (37%) 0 2 (1-9)

1 (7.1%) 3 (21.4%) 4 (28.6%) 5 (36%) 1 (7.1%) 2 (1-4)

5 (12.2%) 9 (22%) 11(26.8%) 15 (36.5%) 1 (2.4%) 2 (1-9)

22 11 5 2 7 13 (48.1) 11

9 8 1 1 2 6 (42.8) 5

22 (46.3) 16

2 7 (53.8) 6 (46.2)

1 3 (50.0) 0 (0.0)

3 10 (52.6) 6 (31.6)

* One patient switched from R-CHOP to DA-EPOCH-R after confirmation of DH status, after 1st cycle. Abbreviations: CR (Complete response), PR (Partial response), SD (Stable disease), PD (Progressive disease); R-CHOP (Rituximab, Cyclophosphamide, Doxorubicin, Vincristine, and Prednisone), CVAD (Cyclophosphamide, vincristine, and doxorubicin), DA-EPOCH (dose adjusted Etoposide, Prednisone, Vincristine, Cyclophosphamide, and Doxorubicin), ICE (Ifosfamide, Carboplatin, Etoposide), DHAP (Dexamethasone, Cytarabine, Cisplatin), GCP (Gemcitabine, Carboplatin, Prednisone). † Chimeric antigen receptor T-cell therapy; TREC trial (Bendamustine, Rituximab, Etoposide, Carboplatin); Gemcitabine and Oxaliplatin; Bendamustine; CVAD; Ibrutinib trial; GVD (Gemcitabine, vincristine, dexamethasone); Ibrutinib and Pembrolizumab; Obinutuzumab; GDP (Gemcitabine, Dexamethasone, Cisplatin).

Table 3. RT details for treatment of R/R LBCL Radiotherapy details Non-DHL/THL (N = 27) Time (days) from large grade B-cell 349 (53-3160) lymphoma diagnosis to RT start (median; range) Disease status at RT (%) CR 3 (11.1) PR 5 (18.5) SD 6 (22.2) PD 13 (48.1) ECOG performance status (%) 0 8 (29.6) 1 10 (37.0) 2 3 (11.1) 3 5 (18.5) 4 1 (3.7) Curative intent (vs. palliative) (%) 16 (59.3) Salvage intent (vs. consolidation) (%) 24 (88.9) Gross Tumor Volume (median/mean; 116.9/383.9 mL) Radiotherapy target

DHL/THL (N=14) 275.5 (68-517)

Total (N=41) 289 (533160)

0 (0.0) 0 (0.0) 4 (28.6) 10 (71.4)

3 (7.3) 5 (12.2) 10 (24.4) 23 (56.1)

1 (7.1) 5 (35.7) 5 (35.7) 3 (21.4) 0 (0.0) 4 (28.6) 14 (100.0) 696/1144.4

9 (22.0) 15 (36.6) 8 (19.5) 8 (19.5) 1 (2.4) 20 (48.8) 38 (92.7) 274.5/664.1

Head and neck Axilla Mediastinum and thorax Abdomen/pelvic lymph nodes (LNs)/soft tissues Bone Soft tissue of extremity GI tract Other (Spleen, inguinal LNs, liver/periportal LNs, breast, cutaneous, soft tissue of buttocks) Median radiotherapy dose (range) Curative Palliative Median number of fractions (range) Twice daily treatment Median BED10* (range)

6 1 3 6

0 0 1 6

6 1 4 12

4 3 2 5

3 2 2 1

7 5 4 6

35 (4-57) 38.6 (24-50.4) 20 (4-36) 18 (1-28) 2 42.5 (5.6-74.1)

35 (4-57)

RT completion (%) Receipt of chemo after RT (%)

25 (92.6) 10 (37.0)

35 (20-45) 43.2(22.5-45) 33.3 (20-42) 13 (5-25) 0 44.9 (22.553.1) 13 (92.9) 2 (14.3)

14 (1-28) 2 42.5 (5.674.1) 38 (92.7) 12 (29.3)

Unknown 2 (7.4) Response during RT (%) Yes 14 (51.9) No 2 (7.4) No detectable clinical symptoms 9 (33.3) prior to RT Unknown ** 1 (3.7) Not recorded 1 (3.7) * BED with α/β =10 ** Concurrent steroid or chemotherapy use

2 (14.3)

4 (9.8)

10 (71.4) 2 (14.3) 1 (7.1)

24 (58.5) 4 (9.8) 10 (24.4)

1 (7.1) 0 (0.0)

2 (4.9) 1 (2.4)

Table 4. Radiographic responses to radiotherapy among patients with less than complete response prior to the treatment NonDHL/THL Total DHL/THL Post-RT imaging performed 17 14 31 CT PET/CT In-field response based on imaging CR

12

10

22

5

4

9

17

p-value 11 (64.7)

2 (14.3)

13 (41.9)

PR 2 (11.8) SD 3 (17.6) PD 1 (5.9) * Fisher test for CR vs. non-CR (PR, SD, PD, and other)

2 (14.3) 9 (64.3) 1 (7.1)

4 (12.9) 12 (38.7) 2 (6.5)

0.01*

Table 5. Univariate analysis of clinical and pathologic factors for achieving complete response to radiotherapy for relapsed/refractory large B-cell lymphoma UVA Factors OR P-value Age 0.94 0.09 COO Germinal center B cell-like Reference 0.36 Activated B cell-like 5.14 Unknown 1.03 DHL/THL Non-DHL/THL Reference 0.009 DHL/THL 0.09 Response to initial chemotherapy Reference 0.38 CR Non-CR 3.09 Disease status prior to RT SD Reference 0.014 PD 0.48 PR Infinity* Gross tumor volume 1 0.75 RT dose 1.04 0.31 *All patients with PR prior to RT achieved CR after RT.