Cancer Is Just Half The Battle
Bacterial infections (with pseudomonas being a very common offender) have been a recognized risk of chemotherapy since the 1940's. In fact, the number one cause of chemotherapy-related mortality (save for the likely probability that it induces mutations in genetically unstable cancer cells to produce a more aggressive cancer cell) is infection, resulting from immunosupression.
It is our immune system that fights against cancer cells (like viruses, infections, etc.). Cytotoxic (cell-killing) chemotherapy is notorious for seriously compromising the patient's immune system by killing the cells that mediate immunity. When that immune system is suppressed or compromised, that's when disease sets in.
The body's immune system attacks and eliminates not only bacteria and other foreign substances but also cancer cells. Cancer cells are not foreign to the body but their biological function has been altered in that it doesn't respond to the body's normal mechanisms for controlling cell growth and reproduction (uncontrolled cell growth and reproduction is what causes cancerous tumors). Much of the body's protection against cancer is carried out directly by cells of the immune system rather than by antibodies circulating in the bloodstream.
There are several mechanisms of immunosuppression, the most obvious being the predictable reduction in the white blood cell count following most forms of chemotherapy. The main justification of having medical oncology be a medical specialty unto itself is the expertise it requires to push the envelop with toxic drugs to kill the tumor without killing the patient. The second mechanism of immunosuppression is a reduction in lymphocytes and plasma cells, which also assist in fighting infections.
It's analogous to the old medical specialty of syphilology. There was a big medical specialty called syphilology which existed because of the expertise it took to give toxic cocktails of the various (mostly ineffective drugs). The formulas were quite complicated, but they persisted until the discovery of penicillin, which finally killed off not just the syphillis spirochete but also the specialty of siphilology. I would hopefully expect that something like this will happen with medical oncology, and I would be thrilled if it happened while I was still around to see it.
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