Primary extranodal non-Hodgkin’s lymphoma (NHL): the impact of alternative definitions tested in the Comprehensive Cancer Centre West population-based NHL registry

Annals of Oncology, Jan 2003

Background: The definition of primary extranodal non-Hodgkin’s lymphoma (NHL) is a controversial issue, especially in patients where both nodal and extranodal sites are involved. Patients and methods: The impact of different definitions of primary extranodal NHL on incidence and prognosis is explored using data from a population-based NHL registry. Results: Using liberal criteria, 389 (34%) cases were classified as primary extranodal NHL. Overall survival (OS) rates of nodal and extranodal NHL patients defined this way were comparable; however, extranodal NHL patients had a better disease-free survival (DFS). When strict criteria were applied, 231 cases (20%) were classified as primary extranodal NHL. OS and DFS rates of extranodal NHL patients defined this way were superior to nodal NHL patients; however, the difference in OS was reversed after correction for differences in International Prognostic Index and malignancy grade. Conclusion: This study illustrates the selection bias that is introduced when a strict definition of primary extranodal NHL, that excludes cases with disseminated disease, is used. Patients with primary extranodal NHL were found to have a superior DFS, irrespective of which definition of primary extranodal NHL was used.

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Primary extranodal non-Hodgkin’s lymphoma (NHL): the impact of alternative definitions tested in the Comprehensive Cancer Centre West population-based NHL registry

Annals of Oncology Primary extranodal non-Hodgkin's lymphoma (NHL): the impact of alternative definitions tested in the Comprehensive Cancer Centre West population-based NHL registry A. D. G. Krol S. le Cessie 1 S. Snijder 0 J. C. Kluin-Nelemans P. M. Kluin 2 E. M. Noordijk 0 The Comprehensive Cancer Centre West, Leiden; Departments of 1 Medical Statistics, Leiden University Medical Centre , Leiden 2 Pathology, University Hospital Groningen , Groningen , The Netherlands Background: The definition of primary extranodal non-Hodgkin's lymphoma (NHL) is a controversial issue, especially in patients where both nodal and extranodal sites are involved. Patients and methods: The impact of different definitions of primary extranodal NHL on incidence and prognosis is explored using data from a population-based NHL registry. Results: Using liberal criteria, 389 (34%) cases were classified as primary extranodal NHL. Overall survival (OS) rates of nodal and extranodal NHL patients defined this way were comparable; however, extranodal NHL patients had a better disease-free survival (DFS). When strict criteria were applied, 231 cases (20%) were classified as primary extranodal NHL. OS and DFS rates of extranodal NHL patients defined this way were superior to nodal NHL patients; however, the difference in OS was reversed after correction for differences in International Prognostic Index and malignancy grade. Conclusion: This study illustrates the selection bias that is introduced when a strict definition of primary extranodal NHL, that excludes cases with disseminated disease, is used. Patients with primary extranodal NHL were found to have a superior DFS, irrespective of which definition of primary extranodal NHL was used. Introduction Most non-Hodgkins lymphomas (NHL) arise in lymph nodes or other lymphatic tissues such as the spleen, Waldeyers ring and thymus. Involvement of so-called extranodal organs is a common finding after staging investigation, however, and a substantial part of NHL even arises in these sites. The latter form is often referred to as primary extranodal NHL. Although 2540% of NHL patients present with a primary extranodal lymphoma [14], and numerous papers dealing with extranodal NHL originating in almost every organ in the body have been published, the literature on primary extranodal lymphomas as a group is limited. Moreover, the definition of primary extranodal lymphoma is a controversial issue, especially in patients where both nodal and extranodal sites are involved. In some series on primary extranodal NHL this problem is circumvented, and only patients with localised disease are included [2, 58]. As primary extranodal lymphomas have the potential to disseminate, these series thus present a picture of extranodal NHL that is incomplete. On the other hand, studies that use more liberal criteria for extranodal NHL [1, 4, 913], and include patients with disseminated disease, might erroneously include patients with disease that originated in lymph nodes or other nodal sites. In the Comprehensive Cancer Centre West (CCCW) NHL registry, we were also confronted with the problems associated with the definition of primary extranodal NHL as outlined above, especially in patients with disseminated disease at both nodal and extranodal sites. For these patients, a third pattern of presentation was proposed: extensive disease [14, 15]. Data from our registry were used to define and explore the relevance of this subdivision of NHL in primary nodal, extranodal and extensive involvement. Its prognostic significance was tested, together with the two alternative subdivisions of nodal and extranodal NHL commonly used in the literature, by relating them to prognostic factors, response to therapy and survival. Patients and methods Inclusion criteria and lymphoma classification Included in the CCCW NHL registry were all newly diagnosed NHL patients living in the region covered by the CCCW (determined by postal code). Registration started on 1 June 1981 and ended on 31 December 1989. Once a diagnosis of NHL was made by the hospital pathologist, slides and frozen material were sent for review to a panel of four regional pathologists, experienced in hemato-pathology. Additional immunological and enzymehistochemical techniques were performed to enable classification according to the Kiel classification, with some modifications, and the International Working Formulation. Only patients with a diagnosis of NHL confirmed by the pathology panel were included in the database, while patients with primary cutaneous lymphoma, multiple myeloma, acute lymphoblastic leukaemia and chronic lymphocytic leukaemia, and all cases diagnosed upon post-mortem examination were excluded from registration. After the inclusion of new patients had stopped, the Revised EuropeanAmerican Lymphoma Classification (REAL) for lymphomas was proposed by the International Lymphoma Study Group. As this new scheme for classification of lymphomas wa (...truncated)


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A. D. G. Krol, S. le Cessie, S. Snijder, J. C. Kluin-Nelemans, P. M. Kluin, E. M. Noordijk. Primary extranodal non-Hodgkin’s lymphoma (NHL): the impact of alternative definitions tested in the Comprehensive Cancer Centre West population-based NHL registry, Annals of Oncology, 2003, pp. 131-139, 14/1, DOI: 10.1093/annonc/mdg004