One of the possible consequences of mastectomy is lymphedema of soft tissues of upper extremities on the side of ablated breast as result of cutting and trauma of multiple nerves, lymphatic and blood vessels. This phenomenon is often accompanied by deterioration of blood and lymphatic microcirculation, increasing of stagnation and aggregation ability of thrombocities, limitation of humeral and ulnar joint activity, severe pain and decreasing of myotonus. The developing of new phototherapeutic method based on using of light-emitting diodes (LED) arrays is attempted. This method is just directed on improvement of patient's condition in combination with other traditional methods such as drug therapy, pressure bandaging etc. The main parameters of LED arrays fixed inside cylindrical tube covering pathology region are: wavelength -- 660 nm, intensity range -- 0.5 mW/sm2. To control and study efficiency of phototreatment ultrasonic dopplerography, thermography, electromyography and viscosimetry have been used. During clinical trials in oncology department of Moscow State University of Medicine and Dentistry 128 patients have been treated with following results: patients felt complete disappearance of pain and weightiness sensation in arm, restoration of skin sensitivity and muscle strength. There were statistically proved amelioration of excitation spreading velocity on radial nerve, decreasing of blood viscosity, increasing of blood velocity in main arteries of shoulder and symmetry of temperature distribution.