Interim FDG PET/CT in primary mediastinal diffuse large B-cell lymphoma: really almost useless procedure?

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61989592%3A15110%2F18%3A73588961" target="_blank" >RIV/61989592:15110/18:73588961 - isvavai.cz</a>

Result on the web

<a href="http://dx.doi.org/10.1007/s00259-018-3946-y" target="_blank" >http://dx.doi.org/10.1007/s00259-018-3946-y</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1007/s00259-018-3946-y" target="_blank" >10.1007/s00259-018-3946-y</a>

Result language

angličtina

Original language name

Interim FDG PET/CT in primary mediastinal diffuse large B-cell lymphoma: really almost useless procedure?

Original language description

Dear Sir, We read with great interest the results of a retrospective analysis of interim FDG PET/CT in patients with primary mediastinal B-cell lymphoma (PMBCL) by Lazarovici et al. [1]. This paper could have an extraordinary impact on decision making in clinical practice worldwide. To investigate the prognostic value of interim PET in PMBCL, Lazarovici et al. analysed 36 consecutive patients who underwent PET/CT after four cycles of rituximab/anthracycline-containing regimens (mainly R-ACVBP or R-CHOP). They concluded that interim PET-positive results do not reflect persistence of active disease in the majority of patients. We fully agree with their statement that interim FDG PET/CT in PMBCL has a low positive prognostic value. But there are some major methodological drawbacks which should be clarified before one can accept that “the relapse rate appears similar regardless of interim FDG PET/CT results and interpretation criteria”, as the authors claimed. First, the PET results were expressed as positive or negative according to the International Harmonization Project (IHP) criteria [2] and then retrospectively reassessed using the Deauville criteria [3]. This approach may have biased the results in many ways. The authors state that two different PET/CT systems were used (Siemens Biograph and General Electric Discovery 690 before and after 2011, respectively). Although the authors’ institution fulfils the requirements for EARL accreditation, as seen on the EARL accreditation programme website, it is not clear whether this was the case for both PET/CT systems. It is well known that different reconstruction techniques and settings greatly influence the visual appearance of images as well as the SUVs obtained, with SUVmax showing the largest differences between different reconstructions. We believe that for this type of study, it is crucial to maintain very similar visual and quantitative characteristics of reconstructed images using either the EARL criteria or a different “site-specific” standardization programme. It would be interesting to know whether the imaging facility guaranteed consistent image appearances and SUVmax readings for both PET/CT systems and all retrospectively evaluated patients [4]. Second, there was a very low correlation between the IHP and the Deauville criteria. We cannot imagine an IHP-positive case being scored as Deauville 2 (2 of 17 negative patients) and, conversely, an IHP-negative case as Deauville 4 (5 out of 19 negative patients). Was there any correlation with the type of the PET/CT system used? Third, it should be stressed that the analysis was performed after the fourth chemotherapy cycle, in contrast to previous studies in which the analysis was performed after mid-interim PET or after the second chemotherapy cycle [5, 6]. The timing of PET/CT is crucial for interpretation of the results, at least in patients with diffuse large B-cell lymphoma [7]. Fourth, the authors did not provide data on progression-free survival. It would be useful to know how early progression occurred since PET/CT is not able to predict late relapse. Fifth, besides the tumour itself, the most important factor influencing outcome is the treatment delivered. All patients undergoing radiotherapy and seven of nine (77.7%) receiving autologous stem cell transplantation were in the IHP-negative group. This discrepancy between the PET-positive and PET-negative groups may hinder estimation of the actual predictive power of PET/CT. Finally, we highly appreciate the very important data reported by our French colleagues. However, the above concerns should be addressed to enhance their broad scientific impact. We believe that interim PET/CT in PMBCL is a useful method with a high negative predictive value. Further multicentre studies with application of the EANM/EARL harmonization strategies [8] are needed to overcome all possible confounding phenomena in PMBCL functional imaging. Moreover, the accuracy and positive predictive value of interim PET/CT may be further increased using quantitative methods and probably also with novel PET tracers such as 3′-deoxy-3′-([18F]fluoro)-fluorothymidine in the near future [9, 10].

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

30205 - Hematology

Project

—

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

EUROPEAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING

ISSN

1619-7070

e-ISSN

—

Volume of the periodical

45

Issue of the periodical within the volume

5

Country of publishing house

DE - GERMANY

Number of pages

2

Pages from-to

882-883

UT code for WoS article

000428240200021

EID of the result in the Scopus database

2-s2.0-85044287622