The estimation of host-resistance in cancer
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Abstract:
From the third year after its clinical diagnosis and onward the cancer hazard rate continuously declines. This phenomenon is common to all cancers irrespective of stage, and far less pronounced in other chronic diseases. It is so typical of cancer as to be regarded as a "law of the improving chances of the cancer patient". Although the cancer hazard rate itself is higher than in most other chronic diseases, it always declines while in other chronic diseases it rises. Two kinds of processes operate in cancer: a noxa and host resistance. Throughout cancer progression the organism maintains a delicate equilibrium with the noxa, only its reserves are continuously depleted and when exhausted the noxa overpowers the host's resistance and the patient dies. The hazard rate is inversely proportional to the patient's reserve. Its decline indicates that the host resists the noxa better and better, since however his reserves are limited, he ultimatelly succumbs to it. This phenomenon also shapes cancer age specific incidence and mortality rates. From the age of 15 years and onward the curves ascend in an exponential fashion, gradually tapering off, which is viewed here as a token of a mounting resistance of the organism to the carcinogenic noxa. Host resistance operates also during tumor growth, accounting for the Gompertzian shape of its growth curve. The growth rate of most human tumors progressively decreases and is therefore best described by the Gompertz function which initially rises in an exponential fashion and gradually tapers off. Tumor size and growth rate indirectly reflect the host's condition or reserve. The two tumor attributes are related to the hazard rate in the following manner: Tumor size is proportional to the hazard rate, indicating host reserve. Tumor growth rate is proportional to the hazard rate change, indicating host resistance. Both indicators may be estimated independently and applied to the assessment of the host's reserve and resistance during cancer progression.