Background: : It has long been appreciated that tumor size, lymph node status, and patient survival are related qualities, although how to isolate their interactions has not been obvious, nor has it been obvious how to integrate tumor size and lymph node status into predictions of the risk of death for individual patients.
Methods: : The authors describe a mathematical method, the binary-biological model of cancer metastasis, based on the spread of cancer cells, in which the equations capture the relations between tumor size, lymph node status, and cancer lethality.
Results: : For melanoma, renal cell carcinoma, and breast carcinoma, the relation between tumor size and the risk of cancer death was captured by the SizeOnly equation. For melanoma and breast carcinoma, the relation between tumor size and the presence of cancer in the lymph nodes was captured by using the NodalSizeOnly equation. For lymph node-negative melanoma and breast carcinoma, the relation between tumor size and risk of death was captured by the PrimarySizeOnly equation. For breast carcinoma, the model indicated that each positive lymph node contributed approximately 6% extra risk of death, whereas each millimeter of greatest primary tumor dimension contributed approximately 1% risk of death. For melanoma, each positive lymph node contributed approximately 23% risk of death, whereas each millimeter of primary melanoma thickness contributed approximately 8% risk of death. This information was captured by a pair of linked equations, the Size+Nodes method.
Conclusions: : Both tumor size and the number of positive lymph nodes made independent contributions to the risk of cancer death, as estimated by using the Size+Nodes method. Cancer 2009. (c) 2009 American Cancer Society.