Andrey Kaprin, chief freelance oncologist of the Ministry of Health of the Russian Federation, general director of the National Medical Research Center for Radiology, president of the Association of Oncologists of Russia, named the main mystery in the treatment of cancer. Cancer cells can adapt to treatment and stop responding to therapy, he said. How to solve this problem, scientists and doctors do not yet know. “One of the main mysteries is why we can’t cure it in any way. See how we have progressed (in treatment), but we can’t, because it mutates. This is such a smart cancer,” RIA Novosti quotes Kaprina. He noted that there are cases when a patient is treated with the most complex drugs, but resistance and the drug ceases to act on the tumor. In addition, there are works describing how doctors had to return to the first variant of chemotherapy, since the subsequent ones lost their effectiveness, Andrey Kaprin said.