Wednesday, April 02, 2008

CLL; Assessment of prognosis

In chronic lymphocytic leukaemia, a third of patients never need treatment and have long survival; in another third, an initial indolent phase is followed by disease progression; the remaining third exhibit aggressive disease at onset and need immediate treatment.[95] The Rai and Binet staging systems have enabled individuals with chronic lymphocytic leukaemia to be divided into three prognostic groups (good, intermediate, and poor) and have provided a foundation for clinicians to design therapeutic strategies for the disease. However, with neither the Rai nor the Binet staging system can we predict who in the good prognosis group will develop progressive disease.[96] Several attempts have been made to address this deficiency. Lymphocyte doubling time, the pattern of bone-marrow involvement, and concentrations in serum of β2 microglobulin, thymidine kinase, and soluble CD23 all have some value but also important drawbacks.[97] Lymphocyte counts can double in response to infection, vaccination, and steroid treatment; patterns of marrow involvement need invasive investigation; measurement of thymidine kinase in serum needs a radioassay; and amounts of CD23 and β2 microglobulin indicate both bulk of disease and rates of progression.

As reported above in the section on Genetic abnormalities, chronic lymphocytic leukaemias with mutated immunoglobulin genes have good prognosis and those with unmutated genes show poor prognosis.[67], [68] and [98] The mutational profile of immunoglobulin genes delineates prognostic groups within all Binet's stages.[67] and [99] The IGHV mutational profile has the advantage that it remains constant during clonal evolution, which contrasts with genomic aberrations and serum markers. Since sequencing IGHV genes is seen as costly and time consuming (though this is probably not true), and it is unavailable at most medical facilities, detection of appropriate, reliable surrogate markers for IGHV mutational status has attracted worldwide attention.

An early candidate surrogate marker was expression of CD38. However, although CD38 expression is associated with poor prognosis, its relation to immunoglobulin mutational status remains controversial.[68] and [100] Furthermore, expression of CD38 can change during disease evolution and concerns exist with respect to interlaboratory variations and the definition of the best cutoff value.[97] and [101]

Crespo and colleagues [102] developed a multivariable flow-cytometric test for ZAP70 that showed 95% correlation with IGHV gene mutational status; this finding was confirmed by a similar assay that used a slightly different way of expressing the results.[103] However, these tests used indirect immunofluorescence, and a more convenient assay using direct immunofluorescence gave only 77% concordance with mutational status of IGHV genes.[104] With the direct assay, ZAP70 seemed to be superior to IGHV genes in prediction of time-to-first treatment, whereas in ZAP70-negative patients, IGHV mutational status delineated good from intermediate prognosis.104 So far, this assay has not exported well to other laboratories and considerable dispute remains about how ZAP70 amounts should be estimated.[105]

LPL is consistently overexpressed in patients with unmutated chronic lymphocytic leukaemia and has also been proposed as a surrogate marker.[106] By contrast with ZAP70, which sometimes fails to identify advanced forms of disease, this marker seems to be an independent prognostic factor for individuals with Binet stage B and C disease.[106] and [107] Assay by real-time quantitative PCR is less widely applicable than flow cytometry, but data suggest that this method is as good as IGHV mutational analysis and more reliable than ZAP70 as a prognostic factor.[108]

For laboratories with facilities to measure concentrations in serum of thymidine kinase, high amounts at diagnosis identified patients categorised into good prognosis groups by other biomarkers (IGHV, ZAP70, CD38, del13q14) who subsequently progressed to advanced disease.[109] Measurement of telomere length also refined the prognostic analysis of IGHV unmutated cases. Patients with short telomeres had significantly shorter progression-free and overall survival than did those with long telomeres.[110] Low amounts of the chemokine receptor CXCR3 predict reduced survival independent of IGHV mutations and CD38 levels.[111] The degree of upregulation of CLLU1 is an independent prognostic marker in patients younger than age 70 years.[112]

Although all these markers provide useful prognostic information, the mutational status of IGHV genes and del 17p and del 11q are the most robust prognostic indicators, having been validated in prospective phase III clinical trials. Findings of a US Intergroup study comparing fludarabine with fludarabine plus cyclophosphamide[113] showed that median progression-free survival was significantly lower for patients with del 17p13 or del 11q23 than for those with other cytogenetic findings. Although progression-free survival was longer for individuals with mutated IGHV genes than for those with unmutated genes, the study was insufficiently powered for this finding to reach significance.[113] In the UK Leukaemia Research Fund CLL4 trial comparing fludarabine, fludarabine plus cyclophosphamide, and chlorambucil, the effect of prognostic markers on outcome was assessed prospectively.[114] Importantly, prognostic factors had a greater effect on overall survival than did choice of treatment. Patients with del 17p in more than 20% of cells had a significantly poorer response rate and median overall survival than did all other individuals, whereas those with unmutated IGHV genes or del 11q23 had significantly shorter progression-free and overall survival than did those with mutated IGHV genes, no matter which treatment they were given. Findings of a CALGB 9712 phase II comparison of different schedules of rituximab given with fludarabine [115] showed that median progression-free and overall survival were significantly greater in patients with mutated IGHV genes than in those with unmutated genes. Survival was also significantly increased with the Döhner hierarchical classification of FISH results moving from del 17p13 to del 13q14.

Combinations of prognostic factors might be more useful than individual factors. CD38 and IGHV mutations100 or CD38 and ZAP70[116] and [117] both perform better than any one factor. A scoring system based on six surface molecules (CD62L [SELL], CD54 [ICAM1], CD49c [ITGA3], CD49d [ITGA4], CD38, and CD79B) detectable by flow cytometry has been proposed.118 Another using the easily available factors of age, sex, Rai stage, number of lymph nodes involved, absolute lymphocyte count, and β2 microglobulin has been assessed in many patients.[119]

By multivariate analysis, both Binet staging and IGHV genes retain their independent prognostic significance in chronic lymphocytic leukaemia and are complementary.[67] and [99] As table 2 shows, addition of Binet staging to the mutational profile of immunoglobulin genes and 17p13 deletion, which is the strongest independent prognostic marker, allows segregation of patients into five prognostic subgroups. We do not claim this prognostic system to be definitive; undoubtedly incorporation of other factors will give greater refinement, but it makes use of the best established and validated factors.

In conclusion, recognition of novel biological variables has had a major effect on our understanding of chronic lymphocytic leukaemia. Some variables seem to be of considerable prognostic importance but, as yet, no evidence is available to suggest that changing therapeutic approaches on the basis of these results will lead to improvement in outcome. Prospective clinical trials are needed to address the stratification of patients according to these factors.

References

95 G Dighiero, Unsolved issues in CLL biology and management, Leukemia 17 (2003), pp. 2385–2391.

96 G Dighiero, K Maloum and B Desablens et al., Chlorambucil in indolent chronic lymphocytic leukemia, N Engl J Med 338 (1998), pp. 1506–1514.

97 E Montserrat, Classical and new prognostic factors in chronic lymphocytic leukemia: where to now?, Hematol J 3 (2002), pp. 7–9.

98 K Maloum, F Davi and H Merle-Beral et al., Expression of unmutated VH genes is a detrimental prognostic factor in chronic lymphocytic leukemia, Blood 96 (2000), pp. 377–379.

99 Y Vasconcelos, F Davi and V Levy et al., Binet's staging system and VH genes are independent but complementary prognostic indicators in chronic lymphocytic leukemia, J Clin Oncol 21 (2003), pp. 3928–3932.

100 TJ Hamblin, JA Orchard and RE Ibbotson et al., CD38 expression and immunoglobulin variable region mutations are independent prognostic variables in chronic lymphocytic leukemia, but CD38 expression may vary during the course of the disease, Blood 99 (2002), pp. 1023–1029.

101 P Ghia, G Guida and S Stella et al., The pattern of CD38 expression defines a distinct subset of chronic lymphocytic leukemia (CLL) patients at risk of disease progression, Blood 101 (2002), pp. 1262–1269.

102 M Crespo, F Bosch and N Villamor et al., ZAP-70 expression as a surrogate for immunoglobulin-variable-region mutations in chronic lymphocytic leukemia, N Engl J Med 348 (2003), pp. 1764–1775.

103 JA Orchard, RE Ibbotson and Z Davis et al., ZAP-70 expression and prognosis in chronic lymphocytic leukaemia, Lancet 363 (2004), pp. 105–111.

104 LZ Rassenti, L Huynh and TL Toy et al., ZAP-70 compared with immunoglobulin heavy-chain gene mutation status as a predictor of disease progression in chronic lymphocytic leukemia, N Engl J Med 351 (2004), pp. 893–901.

105 G Marti, A Orfao and C Goolsby, ZAP-70 in CLL: towards standardization of a biomarker for patient management: history of clinical cytometry special issue, Cytometry B Clin Cytom 70 (2006), pp. 197–200.

106 P Oppezzo, Y Vasconcelos and C Settegrana et al., The LPL/ADAM29 expression ratio is a novel prognosis indicator in chronic lymphocytic leukemia, Blood 106 (2005), pp. 650–657.

107 D Heintel, D Kienle and M Shehata et al., High expression of lipoprotein lipase in poor risk B-cell chronic lymphocytic leukemia, Leukemia 19 (2005), pp. 1216–1223.

108 MB van't Veer, AM Brooijmans and AW Langerak et al., The predictive value of lipoprotein lipase for survival in chronic lymphocytic leukemia, Haematologica 91 (2006), pp. 56–63.

109 C Matthews, MA Catherwood and TC Morris et al., Serum TK levels in CLL identify Binet stage A patients within biologically defined prognostic groups most likely to undergo disease progression, Eur J Haematol 77 (2006), pp. 309–317.

110 I Ricca, A Rocca and D Drandi et al., Telomere length identifies two different prognostic subgroups among VH-unmutated B-cell chronic lymphocytic leukemia patients, Leukemia 21 (2007), pp. 697–705.

111 E Ocana, L Delgado-Perez and A Campos-Caro et al., The prognostic role of CXC3R expression by chronic lymphocytic leukemia B cells, Haematologica 92 (2007), pp. 349–356.

112 P Josefsson, CH Geisler and H Leffers et al., CLLU1 expression analysis adds prognostic information to risk prediction in chronic lymphocytic leukemia, Blood 109 (2007), pp. 4973–4979.

113 MR Grever, DM Lucas and GW Dewald et al., Comprehensive assessment of genetic and molecular features predicting outcome in patients with chronic lymphocytic leukemia: results from the US intergroup phase III trial E2997, J Clin Oncol 25 (2007), pp. 799–804.

114 DG Oscier, R Wade and J Orchard et al., Prognostic factors in the UK LRF CLL4 trial, Blood 108 (2005), p. 299.

115 JC Byrd, JG Gribben and BL Peterson et al., Select high-risk genetic features predict earlier progression following chemoimmunotherapy with fludarabine and rituximab in chronic lymphocytic leukemia: justification for risk-adapted therapy, J Clin Oncol 24 (2006), pp. 437–443.

116 I Del Giudice, A Morilla and N Osuji et al., Zeta chain associated protein 70 and CD38 combined predict the time to first treatment in patients with chronic lymphocytic leukemia, Cancer 104 (2005), pp. 2124–2132.

117 R Schroers, F Griesinger and L Trumper et al., Combined analysis of ZAP-70 and CD38 expression as a predictor of disease progression in B-cell chronic lymphocytic leukemia, Leukemia 19 (2005), pp. 750–758.

118 A Zucchetto, R Bomben and M Dal Bo et al., A scoring system based on the expression of six surface molecules allows the identification of three prognostic risk groups in B-cell chronic lymphocytic leukemia, J Cell Physiol 207 (2006), pp. 354–363.

119 WG Wierda, S O'Brien and X Wang et al., Prognostic nomogram and index for overall survival in previously untreated patients with chronic lymphocytic leukemia, Blood 109 (2007), pp. 4679–4685.

4 comments:

~chris said...

I feel that new technologies like HemeScan will provide us with more markers in the next year or so than we will know what to do with.

The great advantage is, that unlike FISH that requires target markers, the matrix chips will be able to look at all the genes for anomalies.

My greatest hope is that researchers don't get mesmerized by separating CLL patients into ever smaller 'buckets' just because they can but rather continue to look at the bigger picture, which is a better outcome for all.

~chris

Anonymous said...

Personally, I don't understand the continued millions of dollars spent on trying to find "better" prognostic indicators. Treatment is necessary, perhaps, when the disease becomes aggressive, and lymphocyte counts double in less than one year or six months, lymph nodes enlarge, or "B" symptoms become evident.

The money spent on looking for more and more prognostic indicators would be better spent on looking for drugs to treat those who are symptomatic, not in some pointless effort to find the one-thousandth 'wonderful' prognostic indicator.

Enough! We already have mutated/unmutated status, ZAP-70, CD38, B2 microglobulin, etc., etc., etc.

Patients are dying while researchers are fiddling around with more and more prognostic indicators!

Terry Hamblin said...

Yes I agree that we already have enough. Vh genes are not difficult to do now and should be routine. The steps are extract the DNA. PCR up with a standard set of primers. Send DNA to a commercial firm for sequencing - $40 tops. Apply sequence to computer program. read result. It takes much less skill than FISH and there is no reason that it should cost more than $100.

The HemeScan is a version of CGH I think. It has some advantages in picking up chromosome gain and loss, but can't do translocations. Unfortunately it finds more than FISH but no-one knows how to interpret it in a CLL context.

justme said...

Thank you for this.