Most of the attention in the media is now focused on the several forms of cancer treatment grouped under the flattering term “Precision Medicine.” I find that the term raises my skepticism index just a bit; it’s like eating establishments labeling themselves “Gourmet Restaurants,” the implication being that joints not so identified are just feeding troughs for the undiscerning masses. What is medicine that is not included in the category “Precision Medicine?” Do we call it “Slapdash Medicine?”
However, subduing my skepticism for the moment, let me concede that the term has some meaning besides the preening. Cancer has typically been classified as to its location – breast, lung, liver, prostate, and so on. This classification carries with it an implicit assumption that all the cancers within each of those classifications more or less resemble one another, and can more or less be treated in the same way. This is where precision medicine is genuinely different. There are many different types of breast cancer, and their treatment, and, perhaps most important, their prognoses, can be very different. The goal of precision medicine is exactly that – to distinguish between the types of cancer, and between individual cancers, and to treat each cancer in the most effective way available.
Before going down that pathway, let me first review a bit about what makes cancer be cancerous. Cancer cells that emerge in different parts of the body do not much resemble one another. They are mutations of entirely different cells. In some cases, the mutations are random errors of transcription of the genetic material. Most of these will simply die off, but in some cases the mutations include features that not only enable the mutated cells to survive, but confer characteristics that make the cells cancerous, such as the proclivity to keep reproducing after the point at which normal cells die off, and the avidity with which they absorb nutrients and grow. In some cases, the mutations are externally caused by such factors as tobacco, sun exposure, and other carcinogens. In any case, different types of cancer cells resemble one another in only a few respects, for example, in the sense that they can genetically shut off the programmed cell death feature than normal cells incorporate, and that they are greedier than normal cells. This has led to forms of treatment that work to some degree in most types of cancer.
In a previous installment which posted on October 8, I attempted to describe the current lay of the land in cancer treatment, touching briefly on some more recent developments, but focusing mostly on the improvements and refinements in the standard treatment forms, which are after all the treatments modalities employed in the great majority of patients. Those are surgery, chemotherapy, and radiation therapy. To recap briefly, I pointed out that each of these forms of treatment has been immensely improved since they were first introduced, and I noted the genuinely good results achieved in some of the most commonly-occurring types of cancer.
The differences between cancers affecting a single location can be highly significant, and teasing out these differences requires a level of investigation far more intensive than distinguishing between different bacterial pathogens. Researchers have to delve deeply into the structure of the individual cancer cells, down to the structure of the genetic material that determines the cancer’s behavior. Among the most promising developments in cancer research are tools that permit researchers to investigate the DNA of cancer cells, and also in some cases to alter the DNA of cells in the human immune system so that these cells are able to attack cancer cells. There tools are known by their abbreviations – CRISPR-Cas9 and CAR-T.
CRISPR-Cas9 stands for clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9, if you want to know. Some bacteria have evolved a genome-editing technique which lets them capture snippets of DNA from invading viruses and use them to create DNA segm