Sunday, September 5, 2010

Precancer: missed opportunities for diagnosis

"And what physicians say about disease is applicable here: that at the beginning a disease is easy to cure but difficult to diagnose; but as time passes, not having been treated or recognized at the
outset, it becomes easy to diagnose but difficult to cure. The same thing occurs in affairs of state; for by recognizing from afar the diseases that are spreading in the state (which is a gift given only to a prudent ruler), they can be cured quickly; but when they are not recognized and are left to grow to the extent that everyone recognizes them, there is no longer any cure."

- Niccolo Machiavelli

Today's blog continues yesterday's discussion of the precancers. The theme of all these blogs is that precancers, the lesions that precede the development of cancers, can be easily treated. Treatment of all precancers will lead to the eradication of all human cancers.

One of the obstacles in the treatment of the precancers comes from the reluctance of many pathologists and oncologists to recognize precancers when they see them. If you don't recognize the precancers, the clinical trials for new cancer chemotherapeutic agents becomes virtually uninterpretable.

Here's an example:

Suppose you have a new drug that targets a specific gene that is altered in a particular type of cancer. You collect a group of patients with the cancer, and you treat them with your drug, comparing their response to a group of cancer patients who are treated with conventional chemotherapy. You find that 10% of your patients respond well to the drug, and 90% don't respond at all. On average, the group of people who received the new drug had a shorter survival than the group who received conventional chemotherapy. You abandon your new drug.

Now suppose that your population of patients did not all have the same cancer. Suppose that 10% of them actually had a precancerous lesion, and this population accounted for the good responders in your experimental treatment group. In this case, your new therapy failed miserably as a treatment for people with developed cancers, but it succeeded remarkably well as a treatment for precancers.

Unless you have a way of distinguishing the precancers from the cancers, you cannot adequately assess the results of a clinical trial that includes a subset of people who have the precancerous lesion!

If you are a pathologist or an oncologist, you might be thinking that this cannot occur. Patients accrued to clinical trials are carefully evaluated to ensure that they all have the same cancer and have not been misdiganosed [with precancers]. In tomorrow's blog I will show that this is not always the case. In fact, the blurring of precancers with cancers is a prevalent, but avoidable, obstacle to progress against cancer.

- © 2010 Jules Berman

About Precancer: The Beginning and the End of Cancer. Nearly every type of cancer passes through a precancer phase, during which it cannot metastasize or invade other tissues. While medicine is not always successful in treating or curing advanced stages of cancers, recent advances in our understanding of carcinogenesis have helped us to develop strategies to prevent, diagnose, and treat many cancers at the precancer stage. Research in this field is escalating rapidly as the evidence increasingly shows that the number of annual cancer deaths could be drastically reduced through the effective treatment and cure of precancer lesions. This book begins by explaining why it has been so difficult to cure cancers, followed by a review of precancer biology, with descriptions of the most common precancer lesions. The final chapters provide practical socio-political and medical goals for precancer treatment, including discussions of the economics and politics of treating precancers.