Brain tumor will be cured by viruses
Viruses will help defeat cancer
Vladimir Fradkin, Deutsche Welle
Doctors rarely manage to overcome a malignant brain tumor once and for all: usually after a year or two, or even earlier, a relapse occurs. Now German doctors have proposed a new approach to solving the problem.
Glioblastoma is the most common and the most malignant of all brain tumors. In Germany, about 3.5 thousand cases of this disease are registered annually, about half of the patients die already in the first year and a half after diagnosis.
This tumor is often called brain cancer, which is not entirely true, since glioblastoma, unlike carcinoma, that is, cancer itself, develops from so-called glial, not epithelial cells. But this, as they say, does not make it easier for the patient: the tumor grows quickly, grows into the brain tissue and at the same time has no clearly defined boundaries.
Despite the significant progress made in recent years in the field of imaging and technical support for neurosurgical operations, the complete removal of glioblastoma is still a rather difficult and risky task, especially when the tumor is located in critical functional areas of the brain. The fear of excising the excess and thereby causing severe complications in the patient, such as limb paralysis, speech disorders or vision loss, makes neurosurgeons act sometimes with excessive caution. Meanwhile, the remaining tumor cells that have not been removed, as a rule, quickly cause a recurrence of the tumor.
Parvoviruses cure ratsAnd now the world's first clinical trials of a new glioblastoma treatment technique using parvoviruses have begun at the German Cancer Center in Heidelberg.
Parvoviruses are a genus of small, about 20 nanometers in diameter, DNA–containing viruses of spherical shape that do not have an outer shell.
A number of features peculiar to the process of reproduction of parvoruses led scientists to the idea that they should mainly affect and destroy tumor cells, in particular, glioblastoma cells.
Last year, this hypothesis was tested during experiments on rats – and was confirmed. Professor Jean Rommelaere, head of the Department of Tumor Virology at the German Cancer Center, explains: "We started by injecting viruses directly into the tumor. Then they began to inject viruses into the blood of experimental animals, then a nasal spray was used. At the same time, we had to increase the dosages to achieve the effect. But in all three cases, we managed to create the conditions under which the tumors in all the experimental rats disappeared."
The world's first human trialsIt was unclear how parvoviruses would affect human glioblastoma.
Therefore, a project with the participation of 18 patients has recently been launched at the Heidelberg University Clinic. Each of them was diagnosed with a recurrence of glioblastoma, that is, a re-growth of the tumor in place of the previously removed one. The patients were divided into two groups of nine people.
In patients of the first group, a catheter is inserted into the tumor during surgery, and a solution containing viruses is slowly and carefully fed through it in order to infect tumor cells. In patients of the second group, the same solution is administered intravenously. "This study is extremely important for us, among other things, also because," says neurosurgeon Karsten Geletneky, "we were able to compare the effectiveness of two types of viral therapy – local and general."
After ten days of such preparation, all patients undergo surgery to remove glioblastoma. At the same time, surgeons inject another portion of viruses into the operating field. "A surgeon can never remove every single tumor cell," explains Professor Rommeler, "and this creates prerequisites for relapse. Our hope is that the introduction of viruses first into the tumor, and then into the place from where it was excised, will reduce the likelihood of glioblastoma re-development."
It's too early to talk about complete securityAlthough parvoviruses do not belong to infectious agents that cause serious diseases in humans, Heidelberg doctors cannot give a 100% guarantee of the safety of the viral therapy they offer, and therefore patients participating in its clinical trials are treated not simultaneously, but alternately with an interval of at least three weeks.
"The first patients receive the lowest dose of viruses," says the scientist. "Then we intend to gradually increase the dose, but each subsequent increase is possible only after we are convinced of the complete safety of the previous lower dose."
Whether the new approach to the treatment of glioblastoma justified the hopes of Heidelberg doctors, and most importantly, their patients, will become clear only a few months after the completion of therapy. The results of this project can be summed up no earlier than in one and a half to two years. But even in case of positive results, new clinical trials with a much larger number of participants will definitely be needed – this is the only way to gain reliable statistics. So we are talking about the introduction of a new method of glioblastoma treatment into clinical practice, if it comes, it will not be very soon.
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07.12.2011