2 April 2013
What happens when it’s impossible to tell where the cancer came from?
This morning I attended a great discussion at a bi-weekly meeting known as: Tumor Board. Oncologists will present difficult or interesting / unusual cases of patients they are seeing: diagnoses, observations, treatments, caveats with various forms of new therapies or diagnostic techniques, etc.
Most cancers are categorized by the organ of origin. Think: “breast cancer” or “lung cancer.” Although a “breast cancer” might spread to the lungs, it is still known as a “metastatic breast cancer” not a “lung cancer.” The way that metastatic breast cancer to the lungs is treated most effectively more closely mirrors how “breast cancer” is treated, not “lung cancer.” The organ of the tumor of origin often gives a good proxy for therapies appropriate for a cancer that has spread from that organ as well.
But, what happens when one cannot identify the tumor of origin? Many cancer patients are not diagnosed until cancer has begun to metastasize or spread, and it’s not always obvious from where the cancer originated, especially if tumors are in multiple organs. In the last two decades oncologists have begun to use a panel of protein markers as ways to classify and stratify cancers for appropriate therapy guidelines. For example, it’s possible to differentiate a metastasized breast cancer to the lungs from a lung cancer using specific protein markers for breast cells.
Although it was a big step forward from microscope-based histological assessment alone, the guidelines do not always reflect the underlying biology, and the underlying gap in the particular cancer’s armor.
I’ve discussed this a bit before, but before long it might be possible that all cancer patients have their tumor genome sequenced. In theory, this WOULD reveal all genetic changes that underly an individual’s disease, immediately suggesting the most effective therapy to use with the smallest side-effects. Our traditional means of classifying tumors might become trivial and/or obsolete.
Such a future practice might alleviate problems with identifying the tumor of origin. Going back to tumor board, there was a case of a poor woman that had painful tumors in her abdomen with no obvious organ of origin, and protein markers used were not able to classify it further, either. The oncologists debated about what course of action to take, and were unsure about the most effective chemotherapy regiment.
At that moment I thought about the genomic tools on the horizon and what that might mean if the woman had been diagnosed in, say, 5 or 10 years?