Cooperative interactions between HOX and PBX proteins mediated by a conserved peptide motif

Homeoprotein products of the Hox/HOM gene family pattern the animal embryo through the transcriptional regulation of target genes. We have previously shown that the labial group protein HOXA-1 has intrinsically weak DNA-binding activity due to residues in the N-terminal arm of its homeodomain (M. L. Phelan, R. Sadoul, and M. S. Featherstone, Mol. Cell. Biol. 14:5066-5075, 1994). This observation, among others, suggests that HOX and HOM proteins require cofactors for stable interactions with DNA. We have demonstrated that a putative HOX cofactor, PBX1A, participates in cooperative DNA binding with HOXA-1 and the Deformed group protein HOXD-4. Three Abdominal-B class HOX proteins failed to cooperate with PBX1A. We mapped the interacting domain of HOXD-4 to the YPWMK pentapeptide motif, a conserved sequence found N terminal to the homeodomain of HOXA-1 and many other homeoproteins but absent from the Abdominal-B class. The naturally occurring fusion of the transcriptional activation domain of E2A with PBX1 creates an oncoprotein implicated in human pre-B-cell leukemias (M. P. Kamps, C. Murre, X.-H. Sun, and D. Baltimore, Cell 60:547-555, 1990; J. Nourse, J. D. Mellentin, N. Galili, J. Wilkinson, E. Starbridge, S. D. Smith, and M. L. Cleary, Cell 60:535-545, 1990). A pentapeptide mutation that abolished cooperative interaction with PBX1A in vitro also abrogated synergistic transcriptional activation with the E2A/PBX oncoprotein. The direct contact of PBX family members by the HOX pentapeptide is likely to play an important role in developmental and oncogenic processes.

Cell signaling switches HOX-PBX complexes from repressors to activators of transcription mediated by histone deacetylases and histone acetyltransferases

The Hoxb1 autoregulatory element comprises three HOX-PBX binding sites. Despite the presence of HOXB1 and PBX1, this enhancer fails to activate reporter gene expression in retinoic acid-treated P19 cell monolayers. Activation requires cell aggregation in addition to RA. This suggests that HOX-PBX complexes may repress transcription under some conditions. Consistent with this, multimerized HOX-PBX binding sites repress reporter gene expression in HEK293 cells. We provide a mechanistic basis for repressor function by demonstrating that a corepressor complex, including histone deacetylases (HDACs) 1 and 3, mSIN3B, and N-CoR/SMRT, interacts with PBX1A. We map a site of interaction with HDAC1 to the PBX1 N terminus and show that the PBX partner is required for repression by the HOX-PBX complex. Treatment with the deacetylase inhibitor trichostatin A not only relieves repression but also converts the HOX-PBX complex to a net activator of transcription. We show that this activation function is mediated by the recruitment of the coactivator CREB-binding protein by the HOX partner. Interestingly, HOX-PBX complexes are switched from transcriptional repressors to activators in response to protein kinase A signaling or cell aggregation. Together, our results suggest a model whereby the HOX-PBX complex can act as a repressor or activator of transcription via association with corepressors and coactivators. The model implies that cell signaling is a direct determinant of HOX-PBX function in the patterning of the animal embryo.

PBX and MEIS as non-DNA-binding partners in trimeric complexes with HOX proteins

HOX, PBX, and MEIS transcription factors bind DNA through a homeodomain. PBX proteins bind DNA cooperatively as heterodimers with MEIS family members and also with HOX proteins from paralog groups 1 to 10. MEIS proteins cooperatively bind DNA with ABD-B class HOX proteins of groups 9 and 10. Here, we examine aspects of dimeric and higher-order interactions between these three homeodomain classes. The most significant results can be summarized as follows. (i) Most of PBX N terminal to the homeodomain is required for efficient cooperative binding with HOXD4 and HOXD9. (ii) MEIS and PBX proteins form higher-order complexes on a heterodimeric binding site. (iii) Although MEIS does not cooperatively bind DNA with ANTP class HOX proteins, it does form a trimer as a non-DNA-binding partner with DNA-bound PBX-HOXD4. (iv) The N terminus of HOXD4 negatively regulates trimer formation. (v) MEIS forms a similar trimer with DNA-bound PBX-HOXD9. (vi) A related trimer (where MEIS is a non-DNA-binding partner) is formed on a transcriptional promoter within the cell. (vii) We observe an additional trimer class involving non-DNA-bound PBX and DNA-bound MEIS-HOXD9 or MEIS-HOXD10 heterodimers that is enhanced by mutation of the PBX homeodomain. (viii) In this latter trimer, PBX is likely to contact both MEIS and HOXD9/D10. (ix) The stability of DNA binding by all trimers is enhanced relative to the heterodimers. These findings suggest novel functions for PBX and MEIS in modulating the function of DNA-bound MEIS-HOX and PBX-HOX heterodimers, respectively.

A proline-rich transcriptional activation domain in murine HOXD-4 (HOX-4.2)

The product of the murine Hoxd-4 (Hox-4.2) gene is a transcription factor that acts upon an autoregulatory element in Hoxd-4 upstream sequences (1). Using this activity as an assay in transient transfections of P19 embryonal carcinoma (EC) cells, we performed a mutational analysis to map functional domains in the HOXD-4 protein. The importance of the homeodomain was shown by a single amino acid change in this region that abolished activity. Deletion analysis revealed that many evolutionarily conserved regions outside of the homeodomain were dispensable for activation in our assay. Fusions to the GAL4 DNA-binding domain mapped a transcriptional activation function to the HOXD-4 proline-rich N-terminus. The proline-rich transcription factor AP2 squelched activation by HOXD-4 and by GAL4/HOXD-4 N-terminus fusion proteins. Together, these results suggest that HOXD-4 harbors a transcriptional activation domain of the proline-rich type.

A conserved C-terminal domain in PBX increases DNA binding by the PBX homeodomain and is not a primary site of contact for the YPWM motif of HOXA1

HOX proteins are dependent upon cofactors of the PBX family for specificity of DNA binding. Two regions that have been implicated in HOX/PBX cooperative interactions are the YPWM motif, found N-terminal to the HOX homeodomain, and the GKFQ domain (also known as the Hox cooperativity motif) immediately C-terminal to the PBX homeodomain. Using derivatives of the E2A-PBX oncoprotein, we find that the GKFQ domain is not essential for cooperative interaction with HOXA1 but contributes to the stability of the complex. By contrast, the YPWM motif is strictly required for cooperative interactions in vitro and in vivo, even with mutants of E2A-PBX lacking the GKFQ domain. Using truncated PBX proteins, we show that the YPWM motif contacts the PBX homeodomain. The presence of the GKFQ domain increases monomer binding by the PBX homeodomain 5-fold, and the stability of the HOXA1.E2A-PBX complex 2-fold. These data suggest that the GKFQ domain acts mainly to increase DNA binding by PBX, rather than providing a primary contact site for the YPWM motif of HOXA1. We have identified 2 residues, Glu-301 and Tyr-305, required for GKFQ function and suggest that this is dependent on alpha-helical character.

Myelin instability and oligodendrocyte metabolism in myelin-deficient mutant mice

During the active phase of myelination in myelin-deficient mutant mice (mld), myelin basic protein (MBP) synthesis is defective and the myelin lamellae are uncompacted. In these mutants, we found a fast metabolism of the myelin-associated glycoprotein (MAG) and of sulfatides, and the presence of cholesterol esters and a degradation product of MAG, dMAG, indicating that mld myelin was unstable. The increased synthesis of MAG and Wolfgram protein, two proteins present in uncompacted myelin sheath and paranodal loops, was demonstrated by high levels of messengers. Simultaneously, we found an accumulation of inclusion bodies, vacuoles, and rough endoplasmic reticulum in mld oligodendrocytes. This material was heavily immunostained for MAG. Furthermore, the developmental change between the two molecular forms of MAG (p72MAG/p67MAG) was delayed in mld mice. In 85-d-old mld mice, the MBP content increased and myelin lamellae became better compacted. In these mutants, dMAG was absent and MAG mRNAs were found in normal amounts. Furthermore, the fine structure of mld oligodendrocytes was normal and the MAG immunostaining was similar to age-matched controls. These results support a functional role for MBP in maintaining the metabolic stability and the compact structure of myelin. Furthermore, in the absence of MBP and myelin compaction, the regulation of the synthesis of at least two membrane proteins related to myelin cannot proceed.

18F-FDG PET/CT and Urothelial Carcinoma: Impact on Management and Prognosis-A Multicenter Retrospective Study

Objectives: To evaluate the ability of 18F-labeled fluoro-2-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) to predict survivorship of patients with bladder cancer (BC) and/or upper urinary tract carcinoma (UUTC). Materials: Data from patients who underwent FDG PET/CT for suspicion of recurrent urothelial carcinoma (UC) between 2007 and 2015 were retrospectively collected in a multicenter study. Disease management after the introduction of FDG PET/CT in the diagnostic algorithm was assessed in all patients. Kaplan-Meier and log-rank analysis were computed for survival assessment. A Cox regression analysis was used to identify predictors of recurrence and death, for BC, UUTC, and concomitant BC and UUTC. Results: Data from 286 patients were collected. Of these, 212 had a history of BC, 38 of UUTC and 36 of concomitant BC and UUTC. Patient management was changed in 114/286 (40%) UC patients with the inclusion of FDG PET/CT, particularly in those with BC, reaching 74% (n = 90/122). After a mean follow-up period of 21 months (Interquartile range: 4-28 mo.), 136 patients (47.4%) had recurrence/progression of disease. Moreover, 131 subjects (45.6%) died. At Kaplan-Meier analyses, patients with BC and positive PET/CT had a worse overall survival than those with a negative scan (log-rank < 0.001). Furthermore, a negative PET/CT scan was associated with a lower recurrence rate than a positive examination, independently from the primary tumor site. At multivariate analysis, in patients with BC and UUTC, a positive FDG PET/CT resulted an independent predictor of disease-free and overall survival (p < 0,01). Conclusions: FDG PET/CT has the potential to change patient management, particularly for patients with BC. Furthermore, it can be considered a valid survival prediction tool after primary treatment in patients with recurrent UC. However, a firm recommendation cannot be made yet. Further prospective studies are necessary to confirm our findings.

Comparison between the diagnostic accuracies of 18F-fluorodeoxyglucose positron emission tomography/computed tomography and conventional imaging in recurrent urothelial carcinomas: a retrospective, multicenter study

PURPOSE

To determine the performance accuracy of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) after primary tumor treatment for both bladder cancer (BC) and upper tract urothelial cancer (UTUC). To compare the accuracy of FDG PET/CT with that of contrast-enhanced-ceCT and magnetic resonance imaging (MRI).

METHODS

Data of patients with recurrent urothelial carcinomas (UC) after primary treatment were collected in a retrospective, international multicenter study. Inclusion criteria were (1) patients with a known history of UC in the BC and/or in the UTUC; (2) PET/CT images after curative intent treatment of the primary tumor; (3) conventional imaging modalities (abdominal ceCT or MRI, or total body ceCT, and chest X-ray: called C.I.) performed no more than 3 months from PET/CT; (4) available standard of reference (e.g., histological data or follow-up imaging modalities) for the validation of PET/CT findings. Exclusion criteria were other abdominal tumors, chemotherapy administration prior to and/or concomitant to imaging, and non-urothelial histologic variants. Sensitivities, specificities, positive, and negative predictive values were evaluated for all patients and separately for bladder and UTUC.

RESULTS

Overall, 287 patients were enrolled. Two-hundred thirteen patients underwent cystectomy (74.2%), 35 nephroureterectomy (12.2%), 31 both cystectomy + nephroureterectomy (10.8%), 5 both cystectomy + conservative treatment for UTUC (1.4%), and 3 (1%) other types of nephron-sparing treatments for UTUC. Neoadjuvant and adjuvant treatments were performed in 36 (12.5%) and 111 (38.7%) patients, respectively. Sensitivity and specificity (95% confidence intervals) of PET/CT for the detection of recurrent UC were 94% (91% to 96%) and 79% (68% to 88%), respectively. However, sensitivity was higher for BC than UTUC (95% vs. 85%) while specificity was lower in BC (78% vs. 85% for BC and UTUC, respectively). PET/CT and C.I. findings were available in 198 patients. The results were positively concordant in 137 patients, negatively concordant in 23 patients, and discordant in 38 patients (20 negative at C.I. vs. positive at PET/CT and 18 positives at ceCT/MRI vs. negative at PET/CT) (K Cohen = 0.426; p < 0.001). Sensitivities, specificities, and accuracies (95% confidence intervals) of PET/CT vs. C.I. for the detection of recurrent BC and UTUC were 94% (90% to 97%) vs. 86% (81% to 92%), 79% (67% to 92%) vs. 59% (44% to 74%), and 91% (87% to 95%) vs. 81% (75% to 86%), respectively.

CONCLUSIONS

FDG PET/CT has a high diagnostic accuracy for the identification of recurrent UC, particularly in patients with BC. Moreover, its accuracy outperforms C.I. for both BC and UTUC.

Italian Multicenter Study on Accuracy of 18F-FDG PET/CT in Assessing Bone Marrow Involvement in Pediatric Hodgkin Lymphoma

INTRODUCTION

The present study investigated the utility of fluorine-18 (18F) fluoro-2-deoxy-d-glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) in assessing bone marrow involvement (BMI) compared with bone marrow biopsy (BMB) in newly diagnosed pediatric Hodgkin lymphoma (HL).

PATIENTS AND METHODS

A total of 224 pediatric patients with HL underwent 18F-FDG PET/CT at staging. BMB or follow-up imaging was used as the standard of reference for the evaluation of BMI.

RESULTS

18F-FDG PET/CT was negative for BMI in 193 cases. Of the 193 patients, the findings for 16 were originally reported as doubtful and later interpreted as negative for BMI, with negative findings on follow-up imaging and BMB. At BMB, 1 of the 16 patients (6.25%) had BMI. Of the 193 patients, 192 (99.48%) had negative BMB findings. Thus, the 18F-FDG PET/CT findings were truly negative for 192 patients and falsely negative for 1 patient for BMI.

CONCLUSION

18F-FDG PET/CT showed high diagnostic performance in the evaluation of BMI in pediatric HL. Thus, BMB should be ideally reserved for patients presenting with doubtful 18F-FDG PET/CT findings for BMI.

Vertebral Fractures of Unknown Origin: Role of Computed Tomography-Guided Biopsy

Background

We performed a retrospective evaluation of histological and imaging results of patients submitted to computed tomography (CT)-guided biopsy for vertebral fractures (VFs) of unknown etiology to evaluate the pathological causes of fractures and also to observe the diagnostic results of imaging studies available.

Methods

We retrospectively reviewed all the CT-guided vertebral biopsies performed in our institution in the last 2 years, selecting patients with VF of unknown etiology. We reviewed clinical records, imaging studies, and histological examination results. We compared diagnostic performance of the 2 most sensitive imaging modalities for detection of malignancy on the collapsed vertebral body: magnetic resonance imaging (MRI) and positron emission tomography-CT (PET-CT). Anatomopathological results have been considered the gold standard to assess the diagnostic performance of imaging studies. Age stratification has been performed to understand the distribution of different anatomopathological diagnoses in age groups.

Results

Among 282 CT-guided vertebral biopsies, 36 (12.8%) have been performed to diagnose the etiology of VF of unknown origin. In 26/32 (81.3%), the vertebral biopsy was diagnostic: 8 osteopenia, 6 multiple myelomas, 4 osteomyelitis, 2 eosinophilic granuloma, 3 metastases, 1 mastocytosis, 1 Paget's disease, and 1 dysmielopoiesis. In 6 cases, the anatomopathological diagnosis was normal bone structure, most likely excluding malignancy. There were no statistically significance differences between MRI and PET-CT results (P = 1.0000).

Conclusions

Multiple myeloma and osteopenia represent the most frequent causes of this condition in adult patients, while eosinophilic granuloma and osteomyelitis in pediatric patients. Computed tomography-guided biopsy permits one to reach diagnosis in most of cases. Both PET and MRI could be insufficient to discriminate benign from malignant causes of fractures. Computed tomography-guided biopsy is needed when the etiology of fracture remains unclear.

The Value of Semiquantitative Parameters Derived from 18F-FDG PET/CT for Predicting Response to Neoadjuvant Chemotherapy in a Cohort of Patients with Different Molecular Subtypes of Breast Cancer

Pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) is a strong prognostic factor in breast cancer (BC). The aim of this study was to investigate whether semiquantitative parameters derived from baseline [18F]Fluorodeoxyglucose ([18F]FDG) positron emission computed tomography/computed tomography (PET/CT) could predict pCR after NAC and survival outcomes in patients affected by different molecular subtypes of BC. We retrospectively retrieved patients from the databases of two Italian hospitals (Centre A: University Hospital of Ferrara; Centre B: University of Padua) meeting the following inclusion criteria: (1) diagnosis of BC; (2) history of NAC; (3) baseline [18F]FDG PET/CT performed before the first cycle of NAC; (4) available follow-up data (response after NAC and survival information). For each [18F]FDG PET/CT scan, semiquantitative parameters (SUVmax, SUVmean, MTV and TLG) related to the primary tumor (B), to the reference lesion for both axillary (N) and distant lymph node (DN), and to the whole-body burden of disease (WB) were evaluated. Patients enrolled were 133: 34 from centre A and 99 from centre B. Patients' molecular subtypes were: 9 luminal A, 49 luminal B, 33 luminal B + HER-2, 10 HER-2 enriched, and 32 triple negative (TNBC). Luminal A and HER-2 enriched BC patients were excluded from the analysis due to the small sample size. pCR after NAC was achieved in 47 patients (41.2%). [18F]FDG PET/CT detected the primary tumor in 98.3% of patients and lymph node metastases were more frequently detected in Luminal B subgroup. Among Luminal B patients, median SUVmean_B values were significantly higher (p = 0.027) in responders (7.06 ± 5.9) vs. non-responders (4.4 ± 2.1) to NAC. Luminal B + HER-2 non-responders showed a statistically significantly higher median MTV_B (7.3 ± 4.2 cm3 vs. 3.5 ± 2.5 cm3; p = 0.003) and TLG_B (36.5 ± 24.9 vs. 18.9 ± 17.7; p = 0.025) than responders at baseline [18F]FDG PET/CT. None of the semiquantitative parameters predicted pCR after NAC in TNBC patients. However, among TNBC patients who achieved pCR after NAC, 4 volumetric parameters (MTV_B, TLG_B, MTV_WB and TLG_WB) were significantly higher in patients dead at follow-up. If confirmed in further studies, these results could open up a widespread use of [18F]FDG PET/CT as a baseline predictor of response to NAC in luminal B and luminal B + HER-2 patients and as a prognostic tool in TNBC.

Automated Synthesis of 68Ga-DOTA-TOC with a Cationic Purification System: Evaluation of Methodological and Technical Aspects in Routine Preparations

BACKGROUND AND OBJECTIVE

Gallium-68 is a PET isotope available in each nuclear medicine departments, even those not equipped with a cyclotron, since it is easily obtained by eluting compact and transportable generator system. The preparation of Ga-68 DOTA-labeled compounds is performed by remotely controlled automated systems developed in order to ensure production efficiency, reproducibility of the results, fast reaction time, to facilitate the synthesis and minimize the radiation exposure. Many automatic synthesis systems are available on the radiopharmaceutical market, however, they requires some technical adaptations for routine use. We reported the [68Ga]Ga-DOTA-TOC production by automated cassette-based theranostic synthesizer system used in combination with a disposable GMP grade cassette system for cationic purification.

METHODS

The synthesizer is integrated with the 68Ge/68Ga generator systems and it allows to perform elution, eluate purification and radiolabeling in about 38 minutes. We have performed in 2 year (January 2016 - January 2018) over 100 [68Ga]Ga-DOTA-TOC preparations.

RESULTS

The average synthesis yield of radiopharmaceutical production was 54.4 ± 2.3 % and the radiochemical purity average was found 96.94 ± 0.74 %. Only three [68Ga]Ga-DOTA-TOC preparations have failed.

CONCLUSION

The methodology and the adopted technical solutions allowed to obtain a high quality radiopharmaceutical product as required by the European Pharmacopoeia.

Detection rate of 18F-Choline positron emission tomography/computed tomography in patients with non-metastatic hormone sensitive and castrate resistant prostate cancer

AIM

To assess the detection rate of 18F-choline PET/CT in non-metastatic hormone-sensitive prostate cancer (hsPCa) and non-metastatic castrate resistant prostate cancer (CRPCa), based on the criteria proposed in the phase III SPARTAN trial and with high Gleason Score (GS).

METHODS

Between October 2008 and September 2019, data from a retrospective multicenter study (n=4 centers), involving patients undergoing 18F-choline PET/CT scans for a biochemical recurrence of PCa, were collected. The following inclusion criteria were used: 1) histologically proven PCa, 2) a non-metastatic disease in accordance with conventional imaging findings; 3) a PSA doubling time (PSAdt) <10 months, 4) a GS > 8 and 5) no pelvic node > 2 cm. The group of hsPCa and CRPCa patients, were compared by using a non-parametric statistical analysis. Moreover, a logistic regression analysis and ROC curves were used.

RESULTS

140 patients were included. Of these, 82 patients were affected by hsPCa, and 58 had a CRPCa. Overall, 18F-Choline PET/CT was positive in 99/140 (70.7%). It was positive in 55/82 (67.1%) hsPCa patients and in 44/58 (75.9%) CRPCa subjects, respectively. The site of recurrence at 18F-Choline PET/CT were: 16 (27.6%) and 20 (24.4%) in prostatic bed, 25 (43.1%) and 24 (29.3%) in loco-regional lymph nodes and in 27 (46.6%) and 28 (34.1%) in distant organs, respectively for CRPCa and hsPCa patients. The optimal cut-off values for PSA at the time of PET/CT for the prediction or recurrence were 0.5 vs. 2.5 ng/mL for all site of recurrence (AUC: 0.70 vs. 0.72), 0.48 vs. 3.4 ng/mL for prostatic bed (AUC: 0.60 vs. 0.59), 0.5 vs. 1.5 for loco-regional lymph nodes (AUC: 0.62 vs. 0.57) and 2.2 vs. 2.8 ng/mL for distant metastasis (AUC: 0.74 vs. 0.71), respectively in CRPCa and hsPCa (all p=NS). Sensitivities and specificities of 18F-Choline PET/CT for the identification of recurrence disease in all patient population, in hsPCa and CRPCa were 83.7% and 87.5%, 78.9% and 88.9%, 91.4% and 85.7%, respectively.

CONCLUSIONS

the rate of positive 18F-Choline PET/CT is similar in patients with a hsPCa and CRPCa, in case of low PSAdt and high GS. Therefore, non-metastatic PCa patients should be assessed by molecular imaging, in order to adapt the most appropriate therapeutic approach.

Radioligand therapy (RLT) as neoadjuvant treatment for inoperable pancreatic neuroendocrine tumors: a literature review

In the last 10 years, several literature reports supported radioligand therapy (RLT) in neoadjuvant settings for pancreatic neuroendocrine tumors (PanNETs). Indeed, primary tumor shrinkage has been frequently reported following RLT in unresectable or borderline resectable PanNETs. Moreover, RLT-induced intratumoral modifications facilitate surgery, both on primary tumor and metastasis, having a great impact on progression free survival (PFS), overall survival (OS) and quality of life (QoL). However, prospective controlled investigations are necessary to confirm preliminary data and to define the best RLT scheme and the ideal patient that, in a multidisciplinary approach, should be referred to neoadjuvant RLT.

Diagnostic Contribution of Contrast-Enhanced CT as Compared with Unenhanced Low-Dose CT in PET/CT Staging and Treatment Response Assessment of 18F-FDG-Avid Lymphomas: A Prospective Study

The aim of this study was to assess the added diagnostic value of contrast-enhanced CT (CECT) as compared with unenhanced CT (UECT) in PET/CT staging and treatment response assessment of 18F-FDG-avid lymphomas. Methods: 170 PET/UECT scans followed by CECT scans were prospectively performed for staging (n = 85) and for treatment response assessment (n = 85) of 18F-FDG-avid lymphomas, during a single session using an integrated 64-slice PET/CT scanner. CECT and UECT images were evaluated separately by 2 radiologists, whereas PET images were evaluated by 2 nuclear physicians. Nodal and extranodal UECT and CECT findings were classified according to the Lugano criteria and were successively compared with PET/CT results, considered the gold standard. In the analyzed groups, the agreement rate with the disease status determined via PET was calculated separately for UECT and CECT using the McNemar test on paired data. The added value of the contrast medium was shown by the agreement between the PET and CECT results and the lack of agreement between UECT and PET. Results: CECT enabled the identification of additional extranodal lesions (hepatic, muscular, and gastric) in only 3 staging group cases (3.5%), indicating different stages as compared with UECT, whereas there was absolute agreement between CECT and UECT in terms of treatment response assessment. The added diagnostic value of CECT was lower than the established threshold for clinical relevance (15%). The McNemar test indicated no statistical significance in either group. The incidental findings detected by CECT but not UECT were important for clinical management but not sufficient to alter lymphoma treatment strategy. Conclusion: According to our results, it might be possible to exclude CECT examination of 18F-FDG-avid lymphoma from staging and treatment response assessment, with the consequent advantages of reducing radiation exposure and potential contrast-related risks.