A popular science article on the current state of progress towards therapies for cancer based on mobilizing the immune system to attack cancer cells:
More than a century ago, American bone surgeon William Coley came across the case of Fred Stein, whose aggressive cheek sarcoma had disappeared after he suffered a Streptococcus pyogenes infection following surgery to remove part of the large tumor. Seven years later, Coley tracked Stein down and found him alive, with no evidence of cancer. Amazed, Coley speculated that the immune response to the bacterial infection had played an integral role in fighting the disease, and the doctor went on to inoculate more than 10 other patients suffering from inoperable tumors with Streptococcus bacteria. Sure enough, several of those who survived the infection - and one who did not - experienced tumor reduction.
Coley subsequently developed and tested the effect of injecting dead bacteria into tumors, hoping to stimulate an immune response without risking fatal infection, and found that he was able to cause complete regression of cancer in some patients with sarcoma, a type of malignant tumor often arising from bone, muscle, or fat. Unfortunately, with the increasing use of radiation treatments and the advent of systemic chemotherapy, much of Coley's work was abandoned by the time he died in 1936.
Today, however, the use of immune modulation to treat cancer is finally receiving its due. Unlike chemotherapy and radiation treatments, which directly attack cancer cells, immunotherapy agents augment the body's normal immune machinery, increasing its ability to fight tumors. This strategy involves either introducing compounds that directly stimulate the immune cells to work harder, or introducing synthetic proteins that mimic the components of the normal immune response, thereby increasing the body's entire immune reaction. With a handful of therapies already on the market, and dozens more showing promise in all stages of clinical development, these treatments are poised to forever change the way that we approach cancer management.