Background: : Although many prognostic factors are associated with differences in cancer lethality, it may not be obvious whether a factor truly makes an independent contribution to lethality or simply is correlated with tumor size. There is currently no method for integrating tumor size, lymph node status, and other prognostic information from a patient into a single risk of death estimate.
Methods: : The SizeOnly equation, which captures the relation between tumor size and risk of death, makes it possible to determine whether a prognostic factor truly makes an independent contribution to cancer lethally or merely is associated with tumor size (SizeAssessment method). The magnitude of each factor's lethal contribution can be quantified by a parameter, g, inserted into the SizeOnly equation (PrognosticMeasurement method). A series of linked equations (the Size+Nodes+PrognosticFactors [SNAP] method) combines information on tumor size, lymph node status, and other prognostic factors from a patient into a single estimate of the risk of death.
Results: : Nine prognostic factors were identified that made marked, independent contributions to breast carcinoma lethality: grade; mucinous, medullary, tubular, and scirrhous adenocarcinoma; male sex; inflammatory disease; Paget disease; and lymph node status. In addition, it was determined that lymph node status made an independent contribution to melanoma lethality. The SNAP method was able to accurately estimate the risk of death and to finely stratify patients by risk.
Conclusions: : The methods described provide a new framework for identifying and quantifying those factors that contribute to cancer lethality and provide a basis for web-based calculators (available at: http://www.CancerMath.net accessed July 29, 2009) that accurately estimate the risk of death for each patient. Cancer 2009. (c) 2009 American Cancer Society.