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Counsell, Nicholas

https://orcid.org/0000-0002-0688-9192

Mayo Clinic

University College London

Citations 7

Outcomes for Sinonasal Undifferentiated Carcinoma (SNUC): An International Multi-Center Retrospective Cohort Study
Liu, Jacklyn , Takahashi, Yoko , Rehman, Umar , Turri-Zanoni, Mario, Mattavelli, Davide, Counsell, Nicholas , Ferrari, Marco, Rampinelli, Vittorio , Vermi, William , Lombardi, Davide , Saade, Rami , Park, Ki Wan , Emanuel, Oscar , Schartinger, Volker Hans , Franchi, Alessandro , Facco, Carla, Sessa, Fausto, Battocchio, Simonetta , Eriksen, Patrick René Gerhard , Haddouchi, Mohamed El, Maragliano, Roberta , Lelkaitis, Giedrius , Saraswathula, Anirudh, KAUR, RAMAN PREET, Mydlarz, Wojciech K. , Ishii, Masaru, Dave, Manas, Fenton, Tim R. , Lim, Alison E. , Okhovat, Saleh , Elegio, Gyleen, Pouvreau, Pierre, Thariat, Juliette, Digue, L., Ferrand, François-Régis, Costes-Martineau, Valerie, Castain, Claire, Kermadec, H. De , O’Neill, James Paul, Lacy, Peter D., Vaz, Francis, O’Flynn, Paul, Howard, David J., Stimpson, Paul, Wang, S, Royle, Gary , Steele, Christopher, Jay, A., Carnell, Dawn , Forster, Martin D., Thomson, David, Buchwald, Christian von, Lllorente, Jose Luis, Hermsen, Mario A., Jurmeister, Philipp , Capper, David, Gallia, Gary L. , Js, Tay, Mohyeldin, Ahmed, Fernandez-Miranda, Juan, LE, Q, West, Robert B., Patel, Z M, Hwang, P H, Facchetti, Fabio , Nicolai, Piero, Ferrarotto, Renata, Phan, Jack, Bossi, P., Castelnuovo, P., Moya-Plana, Antoine, Verillaud, B., Garnis, Cathie , Thamboo, Andrew , Olawuni, Felicia O., Moore, E.J., Choby, Garret M., Lal, Devyani, Akhave, Neal S. , Bell, Diana , Su, Shirley Y., Lund, Valerie J., London, Nyall R. , HANNA, Ehab, Lechner, Matt, Hwang, Peter H. , Thariat, Juliette , Phan, Jack , Le, Quynh‐Thu , Patel, Zara M. , Franchi, Alessandro , Su, Shirley Y. , Lund, Valerie J. , Lechner, Matt , Castelnuovo, Paolo , Ferrari, Marco , Turri‐Zanoni, Mario , Mattavelli, Davide , Moya‐Plana, Antoine , Rehman, Umar , Turri-Zanoni, Mario , Mattavelli, Davide , Ferrari, Marco , Schartinger, Volker H , Maragliano, Roberta , Lelkaitis, Giedrius , Fenton, Tim R , Thariat, Juliette , Ferrand, Francois-Regis , Howard, David J , Carnell, Dawn , Forster, Martin D , von Buchwald, Christian , Hermsen, Mario , Tay, Joshua K , Le, Quynh-Thu , Patel, Zara , Hwang, Peter H , Facchetti, Fabio , Phan, Jack , Bossi, Paolo , Castelnuovo, Paolo , Moya-Plana, Antoine , Olawuni, Felicia, Su, Shirley Y , Lund, Valerie J , Lechner, Matt , Sessa, Fausto , Bendtsen, Simone K. , Jakobsen, Kathrine Kronberg , Saraswathula, Anirudh , Ramanathan, Murugappan , Ishii, Masaru, Dupin, Charles Louis , Digue, Laurence, Costes‐Martineau, Valérie , Castain, Claire , Hintze, Justin , O'Flynn, Paul E., Steele, Christopher D. , Woods, Robbie , Llorente Pendás, José Luis , Capper, David , Nayak, Jayakar V. , Nicolai, Piero , Vérillaud, Benjamin , Choby, Garret , Hanna, Ehab Y.

Cancers | January 26, 2026 | Volume: 18 | Issue: 3 | Pages: 366

10.3390/cancers18030366 Get It

Background: Sinonasal undifferentiated carcinoma (SNUC) is an extremely rare, high-grade, and aggressive tumor of the sinonasal tract. Due to the rarity of this malignancy, current treatment guidelines are based on small and often/mainly single-center retrospective datasets. In the absence of a universally accepted standard of care for SNUC, treatment approaches vary across countries and institutions, reflecting real-world clinical practice. The primary aim of this study was to describe real-world treatment and outcomes for patients with confirmed SNUC. Methods: This was an international, multi-center, retrospective, observational cohort study that pooled patients into the largest SNUC dataset to date. Fifteen centers were enrolled to contribute data, including seven from Europe, four from the United States, three from the United Kingdom, and one from Canada. In the absence of a universally accepted standard of care for SNUC, treatment approaches varied across countries and institutions, reflecting real-world clinical practice. Patients included were those with histologically confirmed SNUC who were treated between 1997 and 2021. Results: This study yielded 485 patients treated for SNUC. The median age at diagnosis was 55.6 years (IQR: 44.5–67.6), and 63.7% were male. Most cases presented at advanced stages, with 70.8% as T4a or T4b. Overall survival (OS) outcomes were available for 412 patients, with a median follow-up of 26.0 months. The 5- and 10-year OS were 47.2% (95% CI: 40.8–53.3%) and 39.6% (95% CI: 32.5–46.6%), respectively. Advanced age, dichotomized T-stage (T4a/b vs. T1–3), M-stage, and orbital involvement were significant poor prognostic factors on univariable analysis (p’s < 0.01). On multivariable analysis, orbital involvement (HR: 2.73, 95% CI: 1.42–5.27, p = 0.003) and distance metastasis stage (HR: 3.00, 95% CI: 1.25–7.21, p = 0.014) were both independently associated with worse OS. Conclusions: This observational study presents the largest multi-center cohort analysis of SNUC to date, providing new insights into prognostic factors for a rare cancer treated at global centers of excellence. Orbital involvement and the presence of metastases are candidate independent risk factors associated with poorer OS.
PET-adaptive beacopp- versus ABVD-based therapies for advanced-stage (AS) classic Hodgkin lymphoma (cHL): Survival comparisons leveraging a multi-state model and analyzing the impact of a-hipi scores across the disease course
Zhu, Cui , Counsell, Nicholas , Upshaw, Jenica , Kirkwood, Amy A. , Advani, Ranjana H. , Gallamini, Andrea , Ghesquières, Hervé , Hutchings, Martin , Johnson, Peter , Advani, Ranjana H , Cui, Zhu, Rodday, Angie Mae , Tighiouart, Hocine , Rossetti, Sára , Li, Hongli , Casasnovas, Olivier , Cerhan, James R. , Federico, Massimo , Hawkes, Eliza A. , Hodgson, David , Link, Brian K. , Mou, Eric , Radford, John , Savage, Kerry J. , Stephens, Deborah M. , Zinzani, Pier Luigi , Maurer, Matthew J. , Rossi, Cédric , Evens, Andrew M. , Parsons, Susan K.

Blood | December 5, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 129-129

10.1182/blood-2025-129 Get It

Abstract Background: Despite recent therapeutic advances in AS cHL, PET-adaptive chemotherapy-based regimens remain a first-line treatment option, especially for patients (pts) without access to novel agents. Most PET-adaptive regiments start with either 2 cycles of escBEACOPP (escBEACOPP2) or ABVD (ABVD2) prior to interim PET assessment (iPET), followed by treatment de-escalation or intensification by iPET result. There have been no direct comparisons of escBEACOPP2 vs ABVD2 PET-adaptive regimens. Additionally, the AS-Hodgkin Lymphoma International Prognostication Index (A-HIPI) score (Rodday JCO 2023) has not been fully explored in escBEACOPP2 regimens. Therefore, we utilized multiple analytic approaches to compare outcomes of PET-adaptive escBEACOPP2 and ABVD2 regimens, while adjusting for and assessing the effect of the baseline A-HIPI score. Methods: Through the global HoLISTIC Consortium (www.hodgkinconsortium.com), we obtained individual patient data from 4 AS clinical trials of newly diagnosed cHL pts treated with PET-adaptive escBEACOPP2 (AHL2011) or ABVD2 (SWOG0816, RATHL, HD0607) regimens. Pts were restricted to age 18 to 65 years (y), stage IIB-IV, and PET-adapted treatment arms. Positive iPET was based on Deauville score &gt;3. Treatment effects of escBEACOPP2 vs ABVD2 (reference) on 5y progression-free survival (PFS) and overall survival (OS) were first evaluated using Cox models. Importantly, baseline disease risk was adjusted for using the 5y PFS or OS A-HIPI score (including stage, sex, age, bulk, lymphocyte count, albumin, white blood cell count), where higher scores indicate higher predicted risk (scale 1-100). The A-HIPI was modeled per 1 standard deviation (SD) increase. Our multistate model (MSM) comprised 4 health states: diagnosis, sustained remission at 1yr, treatment failure, and death from any cause. Pts all started in the diagnosis state and transitioned to other states without return to prior states. We assessed the impact of treatment on transitions (except binary sustained remission at 1y) that involved ≥5 pts per treatment group, adjusting for A-HIPI for all transitions. All effects are reported as adjusted hazard ratios (aHRs) with 95% confidence intervals (CI). Results: 2,381 AS cHL pts were included (n=372 for escBEACOPP2, n=2009 for ABVD2). For escBEACOPP2 and ABVD2 groups (median follow-up 60 and 56 months), respectively, the mean baseline A-HIPI scores (i.e., predicted 5y PFS event rate) were 25.1 (SD=6.3) and 22.9 (SD=6.5), the rates of positive iPET were 11.3% and 17.0%, 5y PFS was 87.0% and 79.5%, and 5y OS was 96.3% and 94.6%. In Cox models, escBEACOPP2 was associated with significantly improved PFS compared to ABVD2 (aHR=0.54, 95% CI=0.39-0.73); the aHR for OS was 0.67 (95% CI=0.37-1.19). Notably, higher risk A-HIPI score was associated with significantly worse PFS (aHR=1.42, 95% CI=1.31-1.54) and OS (aHR=1.60, 95% CI=1.47-1.76), independent of treatment. In the MSM, the effect of escBEACOPP2 compared to ABVD2 regimens was modeled in 3 transitions with adjustment for A-HIPI score: those treated with escBEACOPP2 had lower likelihood of treatment failure with (aHR=0.38, 95% CI=0.22-0.66) or without (aHR=0.61, 95% CI=0.40-0.92) sustained remission at 1y; the aHR for treatment failure to death was 0.55 (95% CI=0.25-1.22). Higher risk baseline A-HIPI score was associated with higher likelihood of treatment failure and death without sustained remission at 1y (aHR=1.43, 95% CI=1.28-1.61 and aHR=2.50, 95% CI=1.80-3.49, respectively). Furthermore, higher risk baseline A-HIPI score was associated with higher likelihood of treatment failure after achieving sustained remission at 1y (aHR=1.29, 95% CI=1.12-1.48) as well as death after treatment failure (aHR=1.54, 95% CI=1.27-1.86). Conclusions: Comparing newly diagnosed adult AS cHL PET-adaptive regimens with adjustment for baseline A-HIPI score, we found pts treated with escBEACOPP2 on AHL2011 had improved PFS versus pooled pt data from 3 ABVD2 trials. Using MSM, we further demonstrated that escBEACOPP2 was associated with a lower likelihood of treatment failure with or without achieving sustained remission at 1yr. In addition, baseline A-HIPI score was associated with PFS and OS, which was independent of treatment. Finally, higher baseline A-HIPI scores maintained prognostic impact throughout the disease course, including increased risk of treatment failure for pts in remission at 1yr and death after treatment failure.
External validation of the early-stage classic Hodgkin lymphoma (cHL) international prognostication index (E-HIPI) in the german Hodgkin study group (GHSG) unfavorable clinical trials
Jablonski, Janina , Borchmann, Sven , Upshaw, Jenica , Counsell, Nicholas , Zhu, Cui , Advani, Ranjana H. , André, Marc, Federico, Massimo, Hoppe, Richard T. , Hutchings, Martin , Borchmann, Peter , Advani, Ranjana H , Hoppe, Richard T , Rodday, Angie Mae , Eichenauer, Dennis A. , Tighiouart, Hocine , Hodgson, David , Maurer, Matthew J. , Rossetti, Sára , Cui, Zhu, Hay, Annette E. , Johnson, Peter , Link, Brian K. , Mou, Eric , Savage, Kerry J. , Radford, John , Cerhan, James R. , Evens, Andrew M. , Parsons, Susan K.

Blood | December 4, 2025 | Volume: 146 | Issue: Supplement 1 | Pages: 1845-1845

10.1182/blood-2025-1845 Get It

Abstract Background: Although progression-free survival (PFS) in early-stage (ES) classic Hodgkin Lymphoma (cHL) is high, there remains a subset of patients (pts) at higher risk of worse outcomes, particularly in those with unfavorable risk disease. Leveraging pt-level data from within the HoLISTIC (Hodgkin Lymphoma International STudy for Individual Care) Consortium, the E-HIPI was developed in clinical trial pts and validated in real-world registry pts to predict 2-year (y) PFS (Rodday. NEJM Evidence 2025). Continuous, objective, and readily measurable pre-treatment variables were considered, with sex, maximum tumor diameter, albumin, and hemoglobin included as significant predictors. Using the E-HIPI, interactive calculators for pt risk, comparison, and stratification were created (https://rtools.mayo.edu/holistic_ehipi/). Although the E-HIPI was developed and validated in both unfavorable and favorable ES cHL pts, the clinical predictors are primarily markers of unfavorable disease. In the development and initial validation cohorts, 2y PFS was 93.7% and 90.3%, respectively, the C-statistic was 0.63 in both cohorts, calibration was strong with slight underprediction of events in the validation cohort, and the E-HIPI outperformed the historic binary classification of patients as favorable or unfavorable using EORTC criteria. However, since pts in the original E-HIPI development and validation were primarily treated with ABVD chemotherapy protocols, additional validation is needed, particularly among pts with unfavorable ES cHL who were treated initially with more intensive chemotherapeutic platforms (e.g., BEACOPP-based). Thus, we conducted an external validation of the E-HIPI in pts treated on recent unfavorable ES cHL GHSG trials. Methods: The validation cohort included 2367 adults (ages 18 to 60y) with newly-diagnosed unfavorable cHL from randomized phase 3 trials conducted by the GHSG (HD14 von Tresckow. JCO 2012; and HD17 Borchmann. Lancet 2021). We calculated the predicted probability of 2y PFS events based on the E-HIPI model equation (scale 1-100%). Model performance was assessed using discrimination and calibration. Discrimination, which is the model's ability to separate high and low risk pts, was assessed using Harrell's C-statistic. Calibration, which is the model's ability to accurately predict absolute risk, was assessed by comparing observed and predicted probabilities of 2y PFS events within quintiles of predicted probabilities and estimating calibration-in-the-large (predicted minus observed event rate) and the calibration slope. Results: For pts treated on unfavorable GHSG trials, mean age was 33y, 95% had stage II disease, mean baseline E-HIPI score (i.e., predicted 2y PFS event rate) was 6.0% (SD=2.3%), and the observed 2y PFS rate was 96.2% (95%CI: 95.4-97.0%). The C-statistic was 0.65 (95% CI: 0.59-0.70), calibration-in-the-large was 0.02, and the calibration slope was 1.08 (95% CI: 0.52, 1.64). Within the lowest risk E-HIPI quintile, the observed 2y PFS event rate was 1.6%, compared with 6.1% in the highest risk quintile. Conclusions: In external validation of the recently published E-HIPI in pts with cHL treated on unfavorable GHSG trials using more intensive BEACOPP-based protocols, discrimination was similar to the original development and validation cohorts. Collectively, the E-HIPI is a treatment-agnostic prediction tool across varied treatment regimens for unfavorable ES cHL pts. Better 2y PFS in the GHSG trials than in the E-HIPI development and initial validation cohorts may have contributed to mild misclassification, likely reflecting differences in treatment regimens. This may be resolved with recalibration or incorporating granular treatment variables into future models. Additional research is needed to understand E-HIPI performance in pts with favorable disease who have even lower event rates as well as to more fully predict individualized pt outcomes across varied chemotherapy platforms and radiation received for all ES cHL pts.
126 | THE EARLY‐STAGE CLASSIC HODGKIN LYMPHOMA INTERNATIONAL PROGNOSTICATION INDEX (E‐HIPI): AN INDIVIDUALIZED PREDICTION MODEL UTILIZING OBJECTIVE AND CONTINUOUS VARIABLES
Rodday, Angie May, Upshaw, Jenica , Counsell, Nicholas , Cui, Zhongguang, Xiang, Qiaojun , Mwangi, Raphael , Gallamini, Andrea , Hay, Alex E. , Raemaekers, John, Evens, Andrew M. , Rodday, Angie Mae , Maurer, Matthew J. , Rossetti, S., Chang, C., Xiang, Q., Advani, Ranjana H. , André, Marc , Hay, A. E., Hodgson, David , Hoppe, Richard T. , Hutchings, Martin , Johnson, Peter , Mou, Eric , Opat, Stephen , Savage, Kerry J. , Parsons, Susan K. , Radford, John

Hematological Oncology | June 16, 2025 | Volume: 43 | Issue: S3 | Pages: No page available

10.1002/hon.70093_126 Get It

Creation of a Multistate Model to Improve Prognostication across the Disease Course in Advanced Stage Classic Hodgkin Lymphoma (cHL): A Report from the Holistic Consortium
Rodday, Angie Mae , Zhu, Cui , Xiang, Qingyan , Counsell, Nicholas , Upshaw, Jenica , Kirkwood, Amy A. , Li, Hongli , Federico, Massimo, Friedberg, Jonathan W. , Gallamini, Andrea , Hutchings, Martin , Evens, Andrew M. , Evens, Andrew M , Parsons, Susan K. , Rossetti, Sára , Williams, Annalynn M , Cerhan, James R. , Hawkes, Eliza A. , Hodgson, David , Johnson, Peter , Link, Brian K. , Mou, Eric , Radford, John , Savage, Kerry J. , Stephens, Deborah M. , Zinzani, Pier Luigi , Maurer, Matthew J.

Blood | December 5, 2024 | Volume: 144 | Issue: Supplement 1 | Pages: 567-567

10.1182/blood-2024-207439 Get It

Background: Although advanced stage cHL typically has excellent disease outcomes, 20-30% of patients (pts) experience treatment failure. In addition, decision-making is challenging given varying treatment options and incomplete prognostic data across the disease course. Pre-treatment factors, such as those incorporated into the Advanced Stage Hodgkin Lymphoma International Prognostication Index (A-HIPI), predict 5 year (y) overall survival (OS) and progression-free survival (PFS) (Rodday JCO 2023). Other than interim PET (iPET) results, it is unknown what factors influence cHL disease states mid-therapy. Using multistate modeling (MSM) and individual pt data from the HoLISTIC Consortium, we refined prognostication across the cHL disease course, specifically assessing the relationships between A-HIPI, iPET and end of treatment (EOT) response, and whether the A-HIPI and iPET provide independent prognostic information. Methods: We analyzed 1240 pts aged 18-65y with newly diagnosed Stage IIB, III or IV cHL treated on 2 advanced stage PET-adapted trials (RATHL, SWOG0816). All pts first received 2 cycles of ABVD; those with a negative iPET (Deauville score (DS) ≤3) received ABVD or AVD, and those with a positive iPET (DS &gt;3) received BEACOPP. In contrast to other methods, MSMs incorporate multiple disease states into one model, account for censoring and competing risks, and estimate transitions between disease states using different covariates. Our MSM had 6 states: diagnosis, negative iPET, positive iPET, EOT non-progression (e.g., DS ≤ 3), treatment failure, and death. Treatment failure included progression or relapse. All pts start at the diagnosis state and can transition to other states without return to prior states. Transition states with &lt;5 events were excluded. The MSM was estimated using a multivariable Cox model with censoring at 5y. Covariates were the 5y PFS A-HIPI (comprised of stage and continuous age, lymphocyte count and albumin), which was included for all transitions, and iPET, which was included for transitions from EOT non-progression and from treatment failure. Higher scores on the 5y PFS A-HIPI indicate lower risk of progression or death; the A-HIPI was modeled for a 1 standard deviation (SD) increase. We calculated probabilities of 5y treatment failure for 4 sample pts based on low (70) and high (85) A-HIPI scores, positive and negative iPET, and EOT non-progression. Results: Median age was 33y (Q1=25, Q3=45), 56% were male, 23% were stage IIB, 40% III and 37% IV, and mean A-HIPI was 77 (SD=7). Median follow-up was 75 months (Q1=53, Q3=92). At iPET, 80% (95% CI 78%, 83%) were negative and 16% (95% CI 14%, 18%) were positive. At EOT, 90% (95% CI 89%, 92%) were in the non-progression state. At 5y, 75% (95% CI 73%, 78%) were in the non-progression state, 16% (95% CI 14%, 19%) had experienced treatment failure, and 9% (7%, 11%) had died. Better A-HIPI scores (per SD) were associated with lower rates of transitioning from diagnosis to positive iPET (HR=0.80, p&lt;0.01) and from positive iPET to treatment failure (HR=0.58, p=0.04). Better A-HIPI scores (per SD) were also associated with lower rates of transitioning from EOT non-progression to treatment failure (HR=0.78, p&lt;0.01) and from treatment failure to death (HR=0.64, p&lt;0.01), adjusting for iPET. Positive iPET was associated with an increased rate of transitioning from EOT non-progression to treatment failure (HR=1.90, p&lt;0.01), adjusting for A-HIPI. The probability of 5y treatment failure for 4 sample pts was: 25% for low A-HIPI and positive iPET; 20% for high A-HIPI and positive iPET; 13% for low A-HIPI and negative iPET; and 12% for high A-HIPI and negative iPET. Conclusions: We created a novel MSM that refines prognostication across the cHL disease course by incorporating pre- and post-treatment factors (e.g., iPET) to estimate transitions to future disease states. Although the A-HIPI was developed using pre-treatment factors to predict 5y OS and PFS, we found that it was also associated with transitions to interim disease states, including iPET and EOT response. The A-HIPI and iPET each provided independent prognostic information, supporting the use of both in estimating cHL outcomes. Future analyses will develop clinical prediction models using MSMs that also incorporate varying frontline and salvage treatments and treatment-specific late effects, with the goal of providing individualized information across the disease course.
Development and Validation of the Early-Stage Hodgkin Lymphoma (HL) International Prognostication Index (E-HIPI): A Report from the Hodgkin Lymphoma International Study for Individual Care (HoLISTIC) Consortium
Evens, Andrew M. , Rodday, Angie Mae , Advani, Ranjana H. , Gallamini, Andrea , Hoppe, Richard T. , Hutchings, Martin , Raemaekers, John, Upshaw, Jenica , Xiang, Qingyan , Counsell, Nicholas , Advani, Ranjana H , Evens, Andrew M , Hoppe, Richard T , Maurer, Matthew J. , André, Marc , Hay, Annette E. , Hodgson, David , Johnson, Peter , Link, Brian K. , Opat, Stephen , Parsons, Susan K. , Radford, John

Blood | December 1, 2023 | Volume: 142 | Issue: Supplement 1 | Pages: 3058-3058

10.1182/blood-2023-173320 Get It

Background: There are a lack of clinical prediction tools in early-stage Hodgkin lymphoma (E-HL). We developed and validated a modern-day model, known as E-HIPI, to predict progression-free survival (PFS) within the first 5 years (y) incorporating detailed individual patient (pt) data from international clinical trials and prospective registry data that were standardized, normalized & harmonized as part of the HoLISTIC Consortium (www.hodgkinconsortium.org). Methods: Model development utilized Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis (TRIPOD) guidelines (Moons, Ann Intern Med 2015) on a cohort of 3,080 newly-diagnosed E-HL pts treated on 4 seminal phase 3 clinical trials (NCIC: Meyer, NEJM 2012; RAPID: Radford, NEJM 2015; EORTC-GELA H9U: Ferme, E ur J Cancer 2017; EORTC/LYSA/FIL H10: Andre, JCO 2017). External validation was done in an independent cohort of 462 E-HL pts from a large registry (Princess Margaret, Toronto). Pts with classic HL, stage I or II disease, and ages 18-65 y were included. The primary outcome was PFS. Cox models were utilized with follow-up truncated at 5 years. Baseline predictors were: sex, stage, B symptoms, histology, number & location of nodal sites, and continuous data values of age, maximum tumor diameter (MTD), white blood cell count (WBC), lymphocyte count, hemoglobin, albumin & erythrocyte sedimentation rate (ESR). Multiple imputation was used for missing data. To consider possible non-linear relationships for continuous variables we examined plots & cubic splines. We used backward elimination ( P&lt;0.1) to develop the models & internal validation with 200 bootstrap samples was conducted to estimate optimism & correct for overfitting. The final prediction equations applied optimism corrections to beta coefficients & hazard ratios (HR). Sensitivity analyses included model results stratified by PET staging (vs CT) and each HL trial. The models were evaluated in the external validation cohort & compared using c-statistics. Model scores were also grouped by tertiles for visualization in Kaplan-Meier (KM) curves. Results: Median age in the development cohort was 35y; 51% were female; 81% had nodular sclerosis & 77% stage II disease; 26% had B symptoms; 32% had mediastinal bulk (≥10cm or &gt;1/3 diameter) and the mean MTD was 6.4 cm (interquartile range (IQR), 3.9-8.2). Median follow-up was 60 months (IQR 45-75). KM estimates at 5y was 90.7% (264 events) for PFS, and 97.1% (78 events) for overall survival (OS). After backward elimination, significant variables retained were age, sex, nodal location (cervical region), MTD & albumin. Stage, ESR, or the number of nodal sites were not significant. Age was modeled with piecewise linear splines due to its non-linear relationship. See the Table for the final prediction model and optimism-corrected HRs. Optimism-corrected c-statistics in the development model was 0.63. Sensitivity analyses of stratification by type of imaging at staging or by each clinical trial demonstrated no change in model parameters or c-statistics. Most baseline characteristics and outcomes of the external validation cohort were similar besides median follow-up time (74 months, IQR 37-129). C-statistics for the E-HIPI model in external validation was 0.63. In addition, observed 5y outcomes stratified by tertile of predicted risk in the external cohort separated pts into a low & higher-risk group, which comprised 1/3 & 2/3 of pts, respectively ( Figure). Finally, model diagnostics revealed the potential for time dependency in the retained covariates. Further assessment of differential prediction between early (&lt;2y) vs. later (2-5y) PFS events is ongoing. Conclusion: Following TRIPOD methodology, we rigorously developed and externally validated the E-HIPI among &gt;3,500 E-HL pts.Discrete risk groups were delineated, and we identified several novel factors, including nodal location, sex & key continuous variables that predict 5y PFS. Additional model refinement is underway, including formal calibration & external validation via other HL registries (Stanford, Mayo/Iowa SPORE). A web-based calculator to simplify application of the E-HIPI will also be presented at ASH. Future planned modeling includes integration of differing treatments & response-adapted imaging via multistate modeling to enrich individualized survival estimates and simulation modeling to predict late consequences.