This is the nineteenth blog in a series of blogs on neoplasia.
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? In this blog, and in the next few blogs, we'll be exploring the properties of common tumors and how they differ from the properties of rare tumors.
As we saw yesterday, the general approach to funding cancer research is to concentrate funding on the common tumors (the most difficut tumors to treat).
Rare tumors are different from common tumors. Differences between rare and common tumors account for the successes in treating some of the rare tumors.
The rare tumors tend to arise from the inside cells of the body, not the surface cells (as per yesterday's post). Among the rare tumors are the tumors of infancy and childhood. Almost none of the tumors of infancy and childhood develop from surface cells. Pediatric tumors do not follow many years of exposure to a carcinogen.
Congenital neoplasms (rare tumors present at birth) have, at most, nine months to develop. This indicates that they do not have the long development phase that characterizes the common tumors. The long development phase of the common tumors contributes to the accumulation of the numerous genetic alterations that are found in all of the common cancers (and absent from the congenital neoplasms).
There are few causes for any particular rare tumor (that is why a rare tumor is rare). A known cause of a rare tumor is likely to be the cause of any example of the rare tumor. The cause might be an inherited mutation, as is the case for inherited retinoblastoma. The cause might be a single exposure to an identified carcinogen at a documented moment in time, as in gestational exposure to diethylstilbestrol resulting in clear cell carcinoma of the cervix in adolescents.
Rare tumors are likely to have a single cause, or a single aberrant pathway, or a sigle inherited gene. By attacking simple changes in the cells of a rare tumor, it might be possible to arrest the growth of the tumor. It is difficult to imagine that knocking out a growth pathway in a heterogeneous population of genetically diverse cells, as we find in the advanced common tumors, will result in a cancer cure.
-Copyright (C) 2008 Jules J. Berman
*An advanced cancer is one that has directly spread extensively from its primary site or that has metastasized to a distant site
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