the first page

Table 1 
PDT remote results for patients with tumors of different histological type

Cytological and histological investigations were performed for all the patients prior to, during and after treatment. 

Over a period up to 1996, PDT was applied to 138 patients (236 tumors). For 47 patients PDT was a first method of treatment, which surgical treatment, radio - and chemotherapy applied for the remaining patients.

After a first PDT course, the tumors have disappeared completely in 72 patients (55 %), have decreased in 32 patients (24 %) by no less than 75 % and in 19 patients (15 %) 0 no less than 50 %. In the case of 8 patients (6 %) PDT was low effective for all or at least one tumor tumors regression was below 50 %).

According to our data, a localization of tumors did not exert considerable inluence on PDT immediate results. 

Table 1 cites remote PDT results for the patients with tumors of a different histological type.

In the process of PDT, possibilities were found out to expand a sphere of applications of this method, for which purpose, new PDT methods have been proposed with the account of localization of a tumor process, the histological form of tumor, its volume and spread:

1. Interarterial PDT for treatment of tumors in the area of a head a neck. 
2. Use of PDT after Nd: YAG - laser destruction in the treatment of difficulty accessible tumorc of big dimensions. 
3. A multiphase prolonged irradiation of sarcoma with light power gradually increased.

On the basis of the obtainable results, one can make a number of conclusions:

1. 1. The photobiological changes of tumor tissues, in the case of PDT depend on the histological type of tumor.
2. Normal PDT is most effective in the case of basal cellular skin cancer. The other histological types of tumor call for modified PDT.

3. PDT for achieving a complete necrosis of tumors of a different histological structure requires the selection of density of light energy absorption: for the necrosis of basal cellular cancer 100-150 J/cm, for the necrosis of planocellular cancer and adenocarcinoma 100-200 J/cm, for the complete melanotic sarcoma necrosis 400 J/cm. The modified PDT performed according to our proposal improves tumor treatment results of different histological structure.
   On comparing the action of various laser system, it should be noted that the direct results, on using a gold vapour laser, were manifest earlier and were more favorable. The remote results of the effect of all the laser systems were roughly the same (cf. The drawing). 

Tumors destruction 
in percentages

weeks after PDT

On treatment of bronchi, trachea, larynx, nasopharynx, the use of GVL facilitated a patients state over a shorter period of time in comparison with other lasers; highly effective was it in treating basal cellular cancer. Possibly the reason behind the earlier direct results of PDT with GVLs is the pulse, nature and high pulsed radiation power of this laser. Besides this GVLs generate short nanosecond pulsed with a peak power of about 10 kW, following at an interval of tens of microseconds, which exceeds a duration of laser pulse upwards of 4.000 times. This circumstance apparently influences a mechanism of inducing a photosensitizer in the tumor tissue. 

More information:
E-mail: iponom@okb.lpi.troitsk.ru
and u101118@dialup.podolsk.ru