SoylentNews is people
SoylentNews
Patients with terminal cancer could "effectively be cured" by the discovery of a pair of drugs which can shrink tumours or bring them under control in nearly 60% of people with advanced melanoma.
In an international trial of 945 patients, treatment with the drugs ipilimumab and nivolumab stopped the cancer advancing for nearly a year in 58% of cases. This was compared with 19% of cases for ipilimumab alone, which resulted in tumours stabilising or shrinking for an average of two and a half months.
The treatment, known as immunotherapy, uses the body's immune system to attack cancerous cells. Researchers say it could replace chemotherapy as the standard treatment for cancer within five years.
[Paper]: http://www.nejm.org/doi/full/10.1056/NEJMoa1504030#t=article
Original Submission
(Score: 4, Informative) by Joe on Thursday June 04 2015, @09:47PM
The drugs used in the trial are both antibodies that target the proteins PD-1 and CTLA-4. These proteins play an important role in down-regulating the immune response, so it doesn't get carried away fighting an infection (chronic inflammation can induce cancer formation) or mistake healthy cells for something that is dangerous (autoimmune disease).
Since the immune system can recognize mutations/disfunctional cells and kill them, there is a selective pressure for cancer cells that can find a way (immunoediting) to down-regulate the immune response before it can kill them.
Drugs that inhibit immunomodulatory proteins have a number of things going for them - immunoediting is a common process employed by cancer, the immune system is incredibly efficient at finding metastasises, and the target proteins are present on healthy immune cells and will not mutate.
https://en.wikipedia.org/wiki/Immunoediting [wikipedia.org]
https://en.wikipedia.org/wiki/Programmed_cell_death_1 [wikipedia.org]
https://en.wikipedia.org/wiki/CTLA-4 [wikipedia.org]
- Joe
(Score: 1, Interesting) by Anonymous Coward on Thursday June 04 2015, @10:02PM
What percent of primary cancer cells that form do you think survive to the point of forming detectable tumors?
(Score: 4, Informative) by Joe on Thursday June 04 2015, @11:13PM
A very small number and it is hard for me to estimate off-hand, but there are probably some estimates derived from data about transgenic mice that contain one or two mutations (tumor initiating cells usually need around 100).
In mice without an immune system you need to inject ~1000 tumor cells to get a tumor, but with an immune system the number is around 1-10 million. This depends on how tumorigenic the cancer is (cancer cells are a heterogenous population, where only a small number have the capablilty of forming a new tumor) and which tissue it is injected into (skin cancer cells will be more successful in the skin than in the blood).
Along the same lines: patients with tumors often have hundreds of circulating cancer cells (that presumably came from the primary tumor) that never find a place to settle or, if they do, that can't actually expand into a new tumor (micrometastases).
- Joe
(Score: 0) by Anonymous Coward on Friday June 05 2015, @12:00AM
So for about 10^9 stem cells in a given tissue, using your estimates by the time a tumor is found 10^6-10^7 lines that were 'precancerous' have already died out. Still there are plenty of stem cells left. Sound about right?