This is the fifteenth blog in a series of blogs on neoplasia.
In the past few blogs, I've been trying to explain the disconnect between cancer survival data and cancer death rate data. The cancer survival data seems to indicate that we're making enormous improvements in cancer treatment. The cancer death rate indicates that Americans are dying from cancer at about the same rate as they had been a half-century ago.
In an earlier blog, I listed over a dozen biases in cancer survival data that contribute to an overly optimistic sense of medical progress. The subsequent blogs explained these biases in some detail. This is the summarizing blog on the topic of survival data interpretation.
An advanced cancer is a cancer that has invaded extensively at its site of origin (i.e., into adjacent organs or into large vessels) or that has metastasized to other sites. Surgeons have been pretty good at curing cancers that are not advanced (i.e., cancers that can be completely resected at their primary sites of growth, before they have metastasized). For the most common cancers of adults (lung, breast, prostate, colon, pancreas, esophagus, liver, and so on), we have not had much luck curing the advanced cancers.
When oncologists discuss improved outcomes for the advanced stage common cancers, they are seldom referring a patient's chances of surviving the cancer. More often than not, they are discussing the length of time that a patient is expected to live following the diagnosis of the cancer. Though survival times are incrementally increasing, clinical trial data cannot support the conclusion that we are near to finding a cure for any of the advanced common cancers.
The only data we have that tells us anything about our progress in the war to conquer cancer is the age-adjusted cancer death rate. This data would indicate that the cumulative progress in preventing, diagnosing and treating cancer, over the past half century, has been small. To some people, these small improvements are encouraging. To others, it has been a sign that we are moving in the wrong direction.
Though there has been little success in curing the advanced common cancers, there has been remarkable success in finding cures for some of the rare cancers, particularly several rare cancers of childhood.
Why is it possible to cure rare cancers? Why would rarity have anything to do with curability? Is it just a coincidence, or is there some fundamental principle involved?
In the next few blogs in this series on neoplasia, we will explore this question.
-Copyright (C) 2008 Jules J. Berman
key words: cancer, tumor, tumour, carcinogen, neoplasia, neoplastic development, classification, biomedical informatics, tumor development, precancer, benign tumor, ontology, classification, developmental lineage classification and taxonomy of neoplasms