Photodynamic therapy for recurrent malignant gliomas

L. Kravetz, I. Medianik, A. Dydykin, N. Karjakin.

State Institution “Research Institute of Traumatology and Orthopedics of Nizhny Novgorod”

of Public Health Ministry of Russian Federation

Treatment of continued growth of malignant gliomas is a more difficult task than treatment of primary tumors. Cases of short relapse-free period showed the ineffectiveness of the adjuvant therapy which had been previously carried out. The possibilities for further treatment by the standard schemes are limited, thus the search of additional measures which have direct influence on the tumor tissue is justified.

Since August 2011 we have initiated the use of photodynamic therapy (PDT) for recurrent gliomas of the cerebral hemispheres. The aim of the study was to evaluate effects of laser radiation on the tumor bed. We analyzed clinical data, special features of CT and MRT dynamics, duration of relapse-free period.

 Materials and methods: 14 patients were treated with recurrent malignant gliomas of the cerebral hemispheres: 10 - with Grade 4 tumors, 4 - to Grade 3. The average age of patients amounted to 52,1 ± 7,8 l years. The state of Karnofsky scale before surgery for Grade 4 was 59 ± 17,3 points, with Grade 3 being 52 ± 5 points. Intervals after first operation for Grade 4 were (on average) 7,0 ± 2,8 months, at Grade 3 were 14,6 ± 11,1 months. A laser with a wavelength of 661 nm and the photosensitizer Photoditazine have been used. The radiation power was 2.0 watt. The light dose was 180 J/cm². The exposure time range was from 14 to 34 minutes.

Results and discussion: Since the first application of FTD 1 patient with partial removal of the tumor died. Continued growth of the tumor in 3 cases recorded only in Grade 4, 3,6 ± 0,6 months after PDT. Reoperation due to recurrent tumor has been performed in 1 case, while indications for surgery were not associated with an increase in tumor size (its volume was less than 10 cm²), but with occlusion of the cerebrospinal fluid pathways.

Analysis of MRT data for tumor recurrence after FTD showed a special topography of regrowth of the tumor tissue. The epicenter of the tumor growth was located at the opposite pole in relation with laser-irradiated areas of the tumor bed, that is actually in the area of brain injury, where there was a radiator and directly around the "dead zones" outside the direct laser exposure were formed

The next clinical results have been positive, except for one case with partial removal of the tumor. In 7 patients a positive trend in neurological status with regression of motor and speech disorders has been received. Average Karnofsky score rose to 68 ± 18, 1 in Grade 4, and 70 ± 11,5 in Grade 3. For greater efficiency FTD further refinement of modes and parameters of exposure is required.