Cancer is the second leading cause of death in the United States and the fifth leading cause of death worldwide. It is generally accepted that as developing nations become more urbanized, their patterns of mortality become more similar to those of economically developed countries. Thus the worldwide burden of cancer is expected to increase dramatically in the coming years.

In the United States, the average annual cancer incidence rate is estimated at 405 per 100,000, and the average annual cancer mortality rate is estimated at 170 per 100,000. For hematologic cancers (including leukemias, lymphomas, and myelomas), the average annual incidence rate is estimated at 33 per 100,000, and the average annual mortality rate is estimated at 17 per 100,000.<sup>48 National Cancer Institute SEER Cancer Statistic Review 1973–1996. Available at: www.seer.ims.nci.nih.gov. Accessed January 5, 2000.

Haga clic aquí para ir a la sección de Referencias</sup> Although overall cancer incidence and mortality rates have been declining since 1992, incidence rates for certain cancers have risen markedly during the same period. For example, between 1973 and 1996 there was an 81% increase in the incidence of non-Hodgkin's lymphoma, a 24% increase in the incidence of acute lymphocytic leukemia, and a 14% increase in the incidence of multiple myeloma. Between 1973 and 1996, mortality rates for non-Hodgkin's lymphoma and multiple myeloma rose by 44% and 36%, respectively.<sup>48 National Cancer Institute SEER Cancer Statistic Review 1973–1996. Available at: www.seer.ims.nci.nih.gov. Accessed January 5, 2000.

Haga clic aquí para ir a la sección de Referencias</sup> It is clear that development of novel strategies to decrease both the incidence and mortality of these diseases is needed. Identification of good prognostic factors is likely to be an important part of the process.

Prognostic factors can help a clinician choose the therapy that is best suited to an individual patient's needs, with the goal of achieving the best possible clinical outcome. Prognostic factors may also be useful in identifying critical steps in the process of carcinogenesis. A factor is considered prognostic if it is associated with tumor development or progression either in the absence or in the application of a specific therapy. Some researchers have made the distinction between factors that predict the natural history of the disease and outcomes under a standard treatment and those that predict response to a new therapy; they designate the former as prognostic factors and the latter as predictive factors.<sup>34 Hayes D., Bast R., Desch C. , y al. Tumor marker utility grading system: A framework to evaluate clinical utility of tumor markers J Natl Cancer Inst 1996 ;  88 : 1456-1466  [cross-ref]

Haga clic aquí para ir a la sección de Referencias</sup> In this article, the term prognostic factor is used for both. The term prognostic biomarker refers to a biochemical or genetic alteration detected in a body tissue or fluid that directly or indirectly reflects an important step in the disease process.<sup>34 Hayes D., Bast R., Desch C. , y al. Tumor marker utility grading system: A framework to evaluate clinical utility of tumor markers J Natl Cancer Inst 1996 ;  88 : 1456-1466  [cross-ref]

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This article reviews the molecular biology of hematologic cancers and the current understanding of prognostic factors for these cancers. Some specific molecular biomarkers that have potential as prognostic factors for various hematologic cancers are discussed. Finally, an overview of quantitative and statistical ways of evaluating the utility of prognostic factors is presented.