PET-guided omission of radiotherapy in early-stage unfavourable Hodgkin lymphoma (GHSG HD17): a multicentre, open-label, randomised, phase 3 trial.

BACKGROUND: Combined-modality treatment consisting of chemotherapy and consolidation radiotherapy is standard of care for patients with early-stage unfavourable Hodgkin lymphoma. However, the use of radiotherapy can have long-term sequelae, which is of particular concern, as Hodgkin lymphoma is frequently diagnosed in young adults with a median age of approximately 30 years. In the German Hodgkin Study Group HD17 trial, we investigated whether radiotherapy can be omitted without loss of efficacy in patients who have a complete metabolic response after receiving two cycles of escalated doses of etoposide, cyclophosphamide, and doxorubicin, and regular doses of bleomycin, vincristine, procarbazine, and prednisone (eBEACOPP) plus two cycles of doxorubicin, bleomycin, vinblastine, dacarbazine (ABVD) chemotherapy (2 + 2). METHODS: In this multicentre, open-label, randomised, phase 3 trial, patients (aged 18-60 years) with newly diagnosed early-stage unfavourable Hodgkin lymphoma (all histologies) and an Eastern Cooperative Oncology Group performance status of 2 or less were enrolled at 224 hospitals and private practices in Germany, Switzerland, Austria, and the Netherlands. Patients were randomly assigned (1:1) to receive either standard combined-modality treatment, consisting of the 2 + 2 regimen (eBEACOPP consisted of 1250 mg/m2 intravenous cyclophosphamide on day 1, 35 mg/m2 intravenous doxorubicin on day 1, 200 mg/m2 intravenous etoposide on days 1-3, 100 mg/m2 oral procarbazine on days 1-7, 40 mg/m2 oral prednisone on days 1-14, 1·4 mg/m2 intravenous vincristine on day 8 [maximum dose of 2 mg per cycle], and 10 mg/m2 intravenous bleomycin on day 8; ABVD consisted of 25 mg/m2 intravenous doxorubicin, 10 mg/m2 intravenous bleomycin, 6 mg/m2 intravenous vinblastine, and 375 mg/m2 intravenous dacarbazine, all given on days 1 and 15) followed by 30 Gy involved-field radiotherapy (standard combined-modality treatment group) or PET4-guided treatment, consisting of the 2 + 2 regimen followed by 30 Gy of involved-node radiotherapy only in patients with positive PET at the end of four cycles of chemotherapy (PET4; PET4-guided treatment group). Randomisation was done centrally and used the minimisation method and seven stratification factors (centre, age, sex, clinical symptoms, disease localisation, albumin concentration, and bulky disease), and patients and investigators were masked to treatment allocation until central review of the PET4 examination had been completed. With the final analysis presented here, the primary objective was to show non-inferiority of the PET4-guided strategy in a per-protocol analysis of the primary endpoint of progression-free survival. We defined non-inferiority as an absolute difference of 8% in the 5-year progression-free survival estimates between the two groups. Safety analyses were done in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT01356680. FINDINGS: Between Jan 13, 2012, and March 21, 2017, we enrolled and randomly assigned 1100 patients to the standard combined-modality treatment group (n=548) or to the PET4-guided treatment group (n=552); two patients in each group were found ineligible after randomisation. At a median follow-up of 46·2 months (IQR 32·7-61·2), 5-year progression-free survival was 97·3% (95% CI 94·5-98·7) in the standard combined-modality treatment group and 95·1% (92·0-97·0) in the PET4-guided treatment group (hazard ratio 0·523 [95% CI 0·226-1·211]). The between-group difference was 2·2% (95% CI -0·9 to 5·3) and excluded the non-inferiority margin of 8%. The most common grade 3 or 4 acute haematological adverse events were leucopenia (436 [83%] of 528 patients in the standard combined-modality treatment group vs 443 [84%] of 529 patients in the PET4-guided treatment group) and thrombocytopenia (139 [26%] vs 176 [33%]), and the most frequent acute non-haematological toxic effects were infection (32 [6%] vs 40 [8%]) and nausea or vomiting (38 [7%] vs 29 [6%]). The most common acute radiotherapy-associated adverse events were dysphagia (26 [6%] in the standard combined-modality treatment group vs three [2%] in the PET4-guided treatment group) and mucositis (nine [2%] vs none). 229 serious adverse events were reported by 161 (29%) of 546 patients in the combined-modality treatment group, and 235 serious adverse events were reported by 164 (30%) of 550 patients in the PET4-guided treatment group. One suspected unexpected serious adverse reaction (infection) leading to death was reported in the PET4-guided treatment group. INTERPRETATION: PET4-negativity after treatment with 2 + 2 chemotherapy in patients with newly diagnosed early-stage unfavourable Hodgkin lymphoma allows omission of consolidation radiotherapy without a clinically relevant loss of efficacy. PET4-guided therapy could thereby reduce the proportion of patients at risk of the late effects of radiotherapy. FUNDING: Deutsche Krebshilfe.

Outcome-based interpretation of early interim PET in advanced-stage Hodgkin lymphoma.

The HD18 study for patients with newly diagnosed advanced-stage Hodgkin lymphoma (HL) used positron emission tomography (PET) after 2 cycles (PET-2) of bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone in escalated doses (eBEACOPP) to guide further treatment. Here, we analyzed the impact of PET-2 results in the context of eBEACOPP according to the Deauville score (DS) in patients treated within the HD18 trial. Residual tissue was visually compared with reference regions according to DS. We analyzed the association between PET-2 uptake and baseline characteristics, progression-free survival (PFS), and overall survival (OS). One thousand five patients (52%) had DS1 or DS2, 471 (24%) had DS3, and 469 (24%) DS4. PET-2 uptake was associated with baseline risk factors large mediastinal mass, extranodal disease, and high International Prognostic Score (P < .0001 each). Among 722 patients receiving standard therapy with 6 cycles of eBEACOPP, 3-year PFS rates were 92.2%, 95.9%, and 87.6% with DS1-2, DS3, and DS4, respectively. Univariate hazard ratio (HR) for PFS in patients with DS4 vs DS1-3 was 2.3 (1.3-3.8; P = .002). DS4 was the only factor remaining significant for PFS in a multivariate analysis including the associated baseline risk factors. Three-year OS rates were 97.6% for DS1-2, 99.0% for DS3, and 96.8% for DS4, with a univariate HR for DS4 vs DS1-3 of 2.6 (1.0-6.6; P = .04). Residual uptake above that in the liver at PET-2 (ie, DS4) is an important risk factor regarding survival outcomes for patients treated with eBEACOPP upfront. We thus recommend DS4 as the cutoff value for PET-2 positivity. This trial was registered at www.clinicaltrials.gov as #NCT00515554.

PET-guided treatment in patients with advanced-stage Hodgkin's lymphoma (HD18): final results of an open-label, international, randomised phase 3 trial by the German Hodgkin Study Group.

BACKGROUND: The intensive polychemotherapy regimen eBEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone in escalated doses) is very active in patients with advanced-stage Hodgkin's lymphoma, albeit at the expense of severe toxicities. Individual patients might be cured with less burdensome therapy. We investigated whether metabolic response determined by PET after two cycles of standard regimen eBEACOPP (PET-2) would allow adaption of treatment intensity, increasing it for PET-2-positive patients and reducing it for PET-2-negative patients. METHODS: In this open-label, randomised, parallel-group phase 3 trial, we recruited patients aged 18-60 years with newly diagnosed, advanced-stage Hodgkin's lymphoma in 301 hospitals and private practices in Germany, Switzerland, Austria, the Netherlands, and the Czech Republic. After central review of PET-2, patients were assigned (1:1) to one of two parallel treatment groups on the basis of their PET-2 result. Patients with positive PET-2 were randomised to receive six additional cycles of either standard eBEACOPP (8 × eBEACOPP in total) or eBEACOPP with rituximab (8 × R-eBEACOPP). Those with negative PET-2 were randomised between standard treatment with six additional cycles of eBEACOPP (8 × eBEACOPP) or experimental treatment with two additional cycles (4 × eBEACOPP). A protocol amendment in June, 2011, introduced a reduction of standard therapy to 6 × eBEACOPP; after this point, patients with positive PET-2 were no longer randomised and were all assigned to receive 6 × eBEACOPP and patients with negative PET-2 were randomly assigned to 6 × eBEACOPP (standard) or 4 × eBEACOPP (experimental). Randomisation was done centrally using the minimisation method including a random component, stratified according to centre, age (<45 vs ≥45 years), stage (IIB, IIIA vs IIIB, IV), international prognostic score (0-2 vs 3-7), and sex. eBEACOPP was given as previously described; rituximab was given intravenously at a dose of 375 mg/m2 (maximum total dose 700 mg). The primary objectives were to show superiority of the experimental treatment in the PET-2-positive cohort, and to show non-inferiority of the experimental treatment in the PET-2-negative cohort in terms of the primary endpoint, progression-free survival. We defined non-inferiority as an absolute difference of 6% in the 5-year progression-free survival estimates. Primary analyses in the PET-2-negative cohort were per protocol; all other analyses were by intention to treat. This trial was registered with ClinicalTrials.gov, number NCT00515554. FINDINGS: Between May 14, 2008, and July 18, 2014, we recruited 2101 patients, of whom 137 were found ineligible before randomisation and a further 19 were found ineligible after randomisation. Among 434 randomised patients (217 per arm) with positive PET-2, 5-year progression-free survival was 89·7% (95% CI 85·4-94·0) with eBEACOPP and 88·1% (83·5-92·7) with R-eBEACOPP (log-rank p=0·46). Patients with negative PET-2 randomly assigned to either 8 × eBEACOPP or 6 × eBEACOPP (n=504) or 4 × eBEACOPP (n=501) had 5-year progression-free survival of 90·8% (95% CI 87·9-93·7) and 92·2% (89·4-95·0), respectively (difference 1·4%, 95% CI -2·7 to 5·4). 4 × eBEACOPP was associated with fewer severe infections (40 [8%] of 498 vs 75 [15%] of 502) and organ toxicities (38 [8%] of 498 vs 91 [18%] of 502) than were 8 × eBEACOPP or 6 × eBEACOPP in PET-2-negative patients. Ten treatment-related deaths occurred: four in the PET-2-positive cohort (one [<1%] in the 8 × eBEACOPP group, three [1%] in the 8 × R-eBEACOPP group) and six in the PET-2-negative group (six [1%] in the 8 × eBEACOPP or 6 × eBEACOPP group). INTERPRETATION: The favourable outcome of patients treated with eBEACOPP could not be improved by adding rituximab after positive PET-2. PET-2 negativity allows reduction to only four cycles of eBEACOPP without loss of tumour control. PET-2-guided eBEACOPP provides outstanding efficacy for all patients and increases overall survival by reducing treatment-related risks for patients with negative PET-2. We recommend this PET-2-guided treatment strategy for patients with advanced-stage Hodgkin's lymphoma. FUNDING: Deutsche Krebshilfe, Swiss State Secretariat for Education and Research, and Roche Pharma AG.

Incorporation of brentuximab vedotin into first-line treatment of advanced classical Hodgkin's lymphoma: final analysis of a phase 2 randomised trial by the German Hodgkin Study Group.

BACKGROUND: A high proportion of patients with relapsed classical Hodgkin's lymphoma achieve a response with the antibody-drug conjugate brentuximab vedotin, and the drug is well tolerated. We modified the escalated BEACOPP regimen (eBEACOPP; bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone) and implemented brentuximab vedotin with the aim to reduce toxic effects while maintaining the protocol's efficacy. METHODS: We did an open-label, multicentre, randomised phase 2 study at 20 study sites in Germany. Adult patients (aged 18-60 years) with newly diagnosed, advanced, classical Hodgkin's lymphoma were randomly assigned (1:1) to treatment with six cycles of either BrECAPP (brentuximab vedotin 1·8 mg/kg on day 1, etoposide 200 mg/m2 on days 2-4, doxorubicin 35 mg/m2 on day 2, cyclophosphamide 1250 mg/m2 on day 2, procarbazine 100 mg/m2 on days 2-8, and prednisone 40 mg/m2 on days 2-15) or BrECADD (brentuximab vedotin 1·8 mg/kg on day 1, etoposide 150 mg/m2 on days 2-4, doxorubicin 40 mg/m2 on day 2, cyclophosphamide 1250 mg/m2 on day 2, dacarbazine 250 mg/m2 on days 3-4, and dexamethasone 40 mg on days 2-5). Randomisation was done centrally by stratified minimisation, with study site and sex as stratification factors. The co-primary endpoints were complete response to chemotherapy and complete remission at the end of treatment, which were assessed by intention to treat. Patients who were found not to meet inclusion criteria after randomisation or without restaging data after two cycles of study treatment were excluded from the primary endpoint analysis. All patients who started study treatment were assessable for safety. This report presents the final analysis at a median follow-up of 17 months (IQR 13·2-21·5). The preplanned 2-year follow-up analysis is yet to be reported. This trial is registered with ClinicalTrials.gov, number NCT01569204. FINDINGS: Between Oct 26, 2012, and May 15, 2014, 104 patients were enrolled to the study (52 were assigned to each study arm). Two patients dropped out before the start of study treatment because of acute infection (n=1) and withdrawal of consent (n=1) and one patient was excluded because of intermediate-stage disease (all were assigned BrECAPP). 42 (86%, 95% CI 73-94) of 49 patients assigned BrECAPP achieved a complete response after chemotherapy and 46 (94%, 95% CI 83-99) had complete remission as their final treatment outcome. In the BrECADD group, 46 (88%, 95% CI 77-96) of 52 patients achieved both a complete response after chemotherapy and complete remission as their final treatment outcome. 58 serious adverse events were reported, 32 events in 21 of 50 patients who received BrECAPP and 26 events in 18 of 52 patients who received BrECADD. The most common grade 3-4 toxic effects were haematological adverse events (91 [89%] of 102 patients). Grade 3-4 organ toxic effects were reported in seven (17%) of 42 patients assigned BrECAPP and two (4%) of 46 allocated BrECADD. 16 (32%) of 50 patients assigned BrECAPP and 18 (35%) of 52 allocated BrECADD had grade 1-2 peripheral neuropathy, and one (2%) patient assigned BrECAPP developed grade 3 peripheral neuropathy; all but one case (allocated BrECAPP) resolved. No deaths were reported during the follow-up period. INTERPRETATION: Both eBEACOPP variants met the co-primary efficacy endpoints. Particularly, the BrECADD regimen was associated with a more favourable toxicity profile and was, therefore, selected to challenge standard eBEACOPP for the treatment of advanced classical Hodgkin's lymphoma in the phase 3 HD21 study by the German Hodgkin Study Group (NCT02661503), which aims to further reduce treatment-related morbidity. FUNDING: Takeda Pharmaceuticals.

Progression-free survival of early interim PET-positive patients with advanced stage Hodgkin's lymphoma treated with BEACOPPescalated alone or in combination with rituximab (HD18): an open-label, international, randomised phase 3 study by the German Hodgkin Study Group.

BACKGROUND: Advanced stage Hodgkin's lymphoma represents a heterogeneous group of patients with different risk profiles. Data suggests that interim PET assessment during chemotherapy is superior to baseline international prognostic scoring in terms of predicting long-term treatment outcome in patients with Hodgkin's lymphoma. We therefore hypothesised that early interim PET-imaging after two courses of bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPP) might be suitable for guiding treatment in patients with advanced stage Hodgkin's lymphoma. We aimed to assess whether intensifying standard chemotherapy (BEACOPPescalated) by adding rituximab would improve progression-free survival in patients with positive PET after two courses of chemotherapy. METHODS: In this open-label, international, randomised, phase 3 study, we recruited patients aged 18-60 years with newly diagnosed, advanced stage Hodgkin's lymphoma from 160 hospitals and 77 private practices in Germany, Switzerland, Austria, the Netherlands, and the Czech Republic. Interim PET-imaging was done after two cycles of BEACOPPescalated and centrally assessed by an expert panel. Patients with a positive PET after 2 cycles of BEACOPPescalated chemotherapy (PET-2) were randomly assigned (1:1) to receive six additional courses of either BEACOPPescalated (BEACOPPescalated group) or BEACOPPescalated plus rituximab (R-BEACOPPescalated group). PET-2 was assessed using a 5-point scale with 18FDG uptake higher than the mediastinal blood pool (corresponding to Deauville scale 3) defined as positive. BEACOPPescalated was given as previously described; rituximab was given intravenously at a dose of 375 mg/m2 (maximum total dose 700 mg), the first administration starting 24 h before starting the fourth cycle of BEACOPPescalated (day 0 and day 3 in cycle 4, day 1 in cycles 5-8). Randomisation was done centrally and used the minimisation method including a random component, stratified according to centre, age, stage, international prognostic score, and sex. The primary efficacy endpoint was 5 year progression-free survival, analysed in the intention-to-treat population. We are reporting this second planned interim analysis as the final report of the trial. The trial is registered with ClinicalTrials.gov, number NCT00515554. FINDINGS: Between May 14, 2008, and May 31, 2011, we enrolled 1100 patients. 440 patients had a positive PET-2 and were randomly assigned to either the BEACOPPescalated group (n=220) or the R-BEACOPPescalated group (n=220). With a median follow-up of 33 months (IQR 25-42) for progression-free survival, estimated 3 year progression-free survival was 91·4% (95% CI 87·0-95·7) for patients in the BEACOPPescalated group and 93·0% (89·4-96·6) for those in the R-BEACOPPescalated group (difference 1·6%, 95% CI -4·0 to 7·3; log rank p=0·99). Common grade 3-4 adverse events were leucopenia (207 [95%] of 218 patients in the BEACOPPescalated group vs 211 [96%] of 220 patients in the R-BEACOPPescalated group), and severe infections (51 [23%] vs 43 [20%] patients). Based on a futility analysis, the independent data monitoring committee recommended publication of this second planned interim analysis as the final result. Six (3%) of 219 patients in the BEACOPPescalated group and ten (5%) of 220 in the R-BEACOPPescalated group died; fatal treatment-related toxic effects occurred in one (<1%) patient in the BEACOPPescalated group and three (1%) in the R-BEACOPPescalated group, all of them due to infection. INTERPRETATION: The addition of rituximab to BEACOPPescalated did not improve the progression-free survival of PET-2 positive patients with advanced stage Hodgkin's lymphoma. However, progression-free survival for PET-2 positive patients was much better than expected, exceeding even the outcome of PET-2-unselected patients in the previous HD15 trial. Thus, PET-2 cannot identify patients at high-risk for treatment failure in the context of the very effective German Hodgkin Study Group standard treatment for advanced stage Hodgkin's lymphoma. FUNDING: Deutsche Krebshilfe; Swiss State Secretariat for Education, Research and Innovation (SERI); and Roche Pharma.

A phase 1 study of the bispecific anti-CD30/CD16A antibody construct AFM13 in patients with relapsed or refractory Hodgkin lymphoma.

AFM13 is a bispecific, tetravalent chimeric antibody construct (TandAb) designed for the treatment of CD30-expressing malignancies. AFM13 recruits natural killer (NK) cells via binding to CD16A as immune effector cells. In this phase 1 dose-escalation study, 28 patients with heavily pretreated relapsed or refractory Hodgkin lymphoma received AFM13 at doses of 0.01 to 7 mg/kg body weight. Primary objectives were safety and tolerability. Secondary objectives included pharmacokinetics, antitumor activity, and pharmacodynamics. Adverse events were generally mild to moderate. The maximum tolerated dose was not reached. Pharmacokinetics assessment revealed a half-life of up to 19 hours. Three of 26 evaluable patients achieved partial remission (11.5%) and 13 patients achieved stable disease (50%), with an overall disease control rate of 61.5%. AFM13 was also active in brentuximab vedotin-refractory patients. In 13 patients who received doses of ≥1.5 mg/kg AFM13, the overall response rate was 23% and the disease control rate was 77%. AFM13 treatment resulted in a significant NK-cell activation and a decrease of soluble CD30 in peripheral blood. In conclusion, AFM13 represents a well-tolerated, safe, and active targeted immunotherapy of Hodgkin lymphoma. A phase 2 study is currently planned to optimize the dosing schedule in order to further improve the therapeutic efficacy. This phase 1 study was registered at www.clinicaltrials.gov as #NCT01221571.

Impact of PET/CT image reconstruction methods and liver uptake normalization strategies on quantitative image analysis.

BACKGROUND: In oncological imaging using PET/CT, the standardized uptake value has become the most common parameter used to measure tracer accumulation. The aim of this analysis was to evaluate ultra high definition (UHD) and ordered subset expectation maximization (OSEM) PET/CT reconstructions for their potential impact on quantification. PATIENTS AND METHODS: We analyzed 40 PET/CT scans of lung cancer patients who had undergone PET/CT. Standardized uptake values corrected for body weight (SUV) and lean body mass (SUL) were determined in the single hottest lesion in the lung and normalized to the liver for UHD and OSEM reconstruction. Quantitative uptake values and their normalized ratios for the two reconstruction settings were compared using the Wilcoxon test. The distribution of quantitative uptake values and their ratios in relation to the reconstruction method used were demonstrated in the form of frequency distribution curves, box-plots and scatter plots. The agreement between OSEM and UHD reconstructions was assessed through Bland-Altman analysis. RESULTS: A significant difference was observed after OSEM and UHD reconstruction for SUV and SUL data tested (p < 0.0005 in all cases). The mean values of the ratios after OSEM and UHD reconstruction showed equally significant differences (p < 0.0005 in all cases). Bland-Altman analysis showed that the SUV and SUL and their normalized values were, on average, up to 60 % higher after UHD reconstruction as compared to OSEM reconstruction. CONCLUSION: OSEM and HD reconstruction brought a significant difference for SUV and SUL, which remained constantly high after normalization to the liver, indicating that standardization of reconstruction and the use of comparable SUV measurements are crucial when using PET/CT.

Follow-up of the GHSG HD16 trial of PET-guided treatment in early-stage favorable Hodgkin lymphoma.

The primary analysis of the GHSG HD16 trial indicated a significant loss of tumor control with PET-guided omission of radiotherapy (RT) in patients with early-stage favorable Hodgkin lymphoma (HL). This analysis reports long-term outcomes. Overall, 1150 patients aged 18-75 years with newly diagnosed early-stage favorable HL were randomized between standard combined-modality treatment (CMT) (2x ABVD followed by PET/CT [PET-2] and 20 Gy involved-field RT) and PET-2-guided treatment omitting RT in case of PET-2 negativity (Deauville score [DS] < 3). The study aimed at excluding inferiority of PET-2-guided treatment and assessing the prognostic impact of PET-2 in patients receiving CMT. At a median follow-up of 64 months, PET-2-negative patients had a 5-year progression-free survival (PFS) of 94.2% after CMT (n = 328) and 86.7% after ABVD alone (n = 300; HR = 2.05 [1.20-3.51]; p = 0.0072). 5-year OS was 98.3% and 98.8%, respectively (p = 0.14); 4/12 documented deaths were caused by second primary malignancies and only one by HL. Among patients assigned to CMT, 5-year PFS was better in PET-2-negative (n = 353; 94.0%) than in PET-2-positive patients (n = 340; 90.3%; p = 0.012). The difference was more pronounced when using DS4 as cut-off (DS 1-3: n = 571; 94.0% vs. DS ≥ 4: n = 122; 83.6%; p < 0.0001). Taken together, CMT should be considered standard treatment for early-stage favorable HL irrespective of the PET-2-result.

Quantitative assessment of 18F-FDG PET in patients with Hodgkin lymphoma: is it significantly affected by contrast-enhanced computed tomography attenuation correction?

OBJECTIVE: The reliability of visual and quantitative response assessment may be impaired owing to inconsistent scanning protocols and image reconstruction methods of 2-deoxy-2-[F]fluoro-D-glucose (F-FDG) PET. Hence, this study investigates the effect of contrast-enhanced computed tomography (CT) attenuation correction in patients with Hodgkin lymphoma. PATIENTS AND METHODS: In 10 consecutive patients undergoing either staging or response assessment, F-FDG PET images were attenuation-corrected once on the basis of unenhanced CT and additionally using contrast-enhanced CT. Reconstruction was performed in both cases with ordered subset expectation maximization (OSEM) and ultra-high definition (UHD) algorithm. While maximum and peak standardized uptake value (SUV) were obtained from tumour tissue (lesionSUVmax and lesionSUVpeak), maximum and mean SUVs were determined within the background regions liver (liverSUVmax and liverSUVmean) and mediastinal blood pool (mbpSUVmax and mbpSUVmean). RESULTS: After switching to contrast-enhanced CT attenuation correction, lesionSUVmax and lesionSUVpeak increased on average by 2.55±3.24 (P=0.018) and 3.64±3.22% (P=0.008), respectively, with OSEM and by 4.59±5.49 (P=0.005) and 3.84±5.65% (P=0.005), respectively, with UHD reconstruction. LiverSUVmax and liverSUVmean showed a mean rise of 7.15±4.27 (P=0.005) and 6.97±2.18% (P=0.005), respectively, in the OSEM data sets and of 7.24±6.59 (P=0.017) and 6.29±2.83% (P=0.005), respectively, in the UHD images. The average increases of mbpSUVmax and mbpSUVmean were 10.82±4.89 (P=0.005) and 12.40±3.73% (P=0.005), respectively, after OSEM, compared with 13.11±14.93 (P=0.005) and 11.50±12.19% (P=0.005), respectively, after UHD reconstruction. CONCLUSION: As the use of CT contrast fluids results in a stronger SUV increase within the liver and mediastinal blood pool than within lymphoma tissue, this may have clinical consequences regarding visual and quantitative response assessment. Ideally, CT scans for PET attenuation correction should therefore be performed in the absence of a contrast agent.