05 May 2010

Cancer vaccine: the second and not the last

Cancer vaccine: apply before death
Irina Yakutenko, "Snob"The U.S. Food, Drug and Cosmetic Administration (FDA) has approved the world's first prostate cancer vaccine.

The medicine, called Provenge, is able to prolong the life of patients for several months. This is the second vaccine against cancer, so we can talk about a positive trend.

Usually, the term "vaccine" means a drug that trains the immune system to fight a particular disease before it enters the body. The drug Provenge is a so–called therapeutic vaccine that stimulates the immune system in people after meeting the "aggressor". Recently, researchers have been actively working on the creation of therapeutic vaccines: drugs for the treatment of kidney cancer and multiple sclerosis have already been created, therapeutic vaccines against hepatitis B, malaria, tuberculosis and even HIV are being developed.

Prostate or prostate cancer is one of the most dangerous oncological diseases, ranking second in mortality among men (lung cancer is the first). The exact causes of prostate cancer are unknown: it is believed that both genes are "to blame" for this process (in men whose relatives have this disease, the risk of getting sick is much higher) and the harmful effects of the environment. One of the important risk factors is food, as well as lifestyle: according to statistics, Japanese people who have moved to the United States develop prostate cancer much more often than their compatriots living at home, and the incidence rate among African Americans is much higher than that of the indigenous population of Africa.

The influence of lifestyle is indirectly confirmed by the data on morbidity in Russia. So far, there are half as many cases of this cancer registered here as the global average. However, the number of cases has been steadily increasing over the past ten years. If this trend does not change, then in another decade Russians will catch up with residents of developed countries – it is there that the largest number of prostate cancer patients are registered.

The vaccine developed by the American company Dendreon Corporation is intended for patients with cancer at the stage of metastasis development (there is a subtlety here: the presence of pain syndrome is a contraindication to its use, so the doctor needs to get into a narrow time window between the spread of metastases and the appearance of pain).

Provenge works like this: blood is taken from the patient and part of the white blood cells are isolated from it, namely T cells and antigen-presenting cells (APC). They are placed in a solution containing proteins; like small pins, these proteins "stick out" on the surface of cancer cells. Spurred on by a special stimulant substance, T cells and APC, like border guard dogs, are trained to recognize and kill cells carrying these proteins. The "trained" cells are returned to the patient's body, where they immediately begin to apply the acquired knowledge. The increased activity of the body's "guards" also determines the side effects of using a new vaccine: fever, runny nose, weakness and sometimes pain.

In clinical trials involving 512 men, the life expectancy of volunteers using Provenge averaged about 25.8 months after completion of the course. Patients who were given a placebo lived for about 21.7 months. Neither received any other treatment: the disease in the study participants was at a stage in which surgery would no longer help, and chemotherapy did not work. Three years after treatment, 32% of men whose cells had learned to resist cancer with the new vaccine were alive, and only 23% of patients who received a placebo. Thus, the vaccine prolonged the life of patients for four months. The effect of its application is still difficult to call revolutionary, but when there is no hope, and these four months are a lot. In 2011, Dendreon Corporation plans to supply vaccines for the treatment of two thousand cancer patients to 50 clinics in the United States where clinical trials were held.

The real importance of creating Provenge can be appreciated if we remember that this is already the second cancer vaccine. The first, Gardasil, helps in almost all cases to prevent infection of women with papillomavirus, which is the main cause of cervical cancer. Clinical trials of Gardasil were completed in 2006, and three years later the vaccine was delivered to medical institutions around the world. Unlike Provenge, Gardasil is a "classic" vaccine that is used before infection with the virus.

Despite the fact that the two drugs differ in their principle of action, their very existence indicates a very encouraging trend: doctors and scientists are learning more and more about the nature of cancer and gradually learning how to fight it. So far, they are only taking the first steps, but, as Lao Tzu said, the path of a thousand li begins with one step. And one more important point: now the Provenge treatment course costs 93 thousand dollars. It seems that as new vaccines become available, their prices will fall.

Portal "Eternal youth" http://vechnayamolodost.ru05.05.2010

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