Laser striking the tumor: new outlook

Russian researchers expect to get answers to these and other questions connected with laser application in medical practice via ascertaining how laser high-intensity impulses act on biotissues, first of all – on pathological tissues. The investigation involves specialists of three biggest national scientific centers.

These are the Troitsk Institute of Innovation and Thermonuclear Investigations, the Blokhin Russian Oncological Scientific Center and the Federal Nuclear Center in Sarov. The subject of inquiry is the tumors located in the ‘near-surface’ skin layers. Specialists are well aware that it is here that up to 95 percent of all malignant skin diseases develop, including mortally dangerous black cancer.

The authors’ expectations are based on the fact that malignant cells and respectively tissues differ in some way from normal ones. Among the differences, two are most important in this case. Firstly, the tumor tissue is as a rule more than ususal penetrated by blood vessels: the tumor grows quickly and therefore needs ‘nourishing diet’. Secondly, uncontrolled dividing tumor cells are characterized by hyperchromatosis of nuclei, i.e., by more intense color. Therefore, one way or another, the tumor differs from its surroundings by spectral characteristics. The researchers decided to take advantage of this fact.

“If the tissue containing malignant cells is affected by a laser impulse of required wave-length, sufficient power and short duration, it can be achieved that the impulse is selectively absorbed and only malignant cells are subsequently destroyed – surrounding healthy cells would not be influenced, explains Ludmila Chernysheva, project manager, main specialist of the direction. To this end, we assume that the impulse should be sufficiently intense, but short, its duration being of several nanoseconds so that macromolecules’ photodisruption took place in the tumor under the impact of radiation, but not macromolecules’ thermal disruption (evaporation or coagulation). By the way, the latter is most important. Otherwise selectivity of influence is lost: both diseased and healthy tissues suffer and there is no guaranty that lesion foci are eliminated completely.

To reveal the optimal irradiation modes – wave-length, power, duration and impulse frequency, under which the effect would be the highest possible but undesirable consequences would be minimal, the authors are planning to act by radiation of different parameters at various biotargets (from standardized test solutions through tissues of laboratory animals). The first experiments have already been carried out, and they bring out clearly that the concept ‘works’.

However, when the impulse duration is decreased, power density increases, which leads to various nonlinear effects. The authors are planning to find out if a short powerful laser impulse possesses (in general and specifically in the modes selected by them) mutagenic and/or cancerogenic action, that is to determine how safe the suggested method is. So far, nobody has dealt systematically with this problem, therefore, the authors believe it necessary to make sure that the method is safe enough.

“As a result, we hope that optimal parameters and laser impact modes will be determined and worked out from the point of view of efficiency and speed of ablation of malignant mass, the lowest degree of injury, cytotoxicity and mutagenic danger, healing times and postoperative complications, as well as ways to deliver radiation into the impact area, continues L.V. Chernysheva. The laser source for oncology and radiation delivery vehicle will be approved on the objects in vitro, and then – in the clinical environment. The determinative selection factor will undoubtedly be the therapeutic effect.”