Tumor growth delay by laser-generated shock waves

The antiproliferative effect of laser-generated shock waves (L-SW) was investigated on a human renal cell carcinoma, RC-8, grown subcutaneously in the nu/nu mouse. The RC-8 is characterized by the syndrome of humoral hypercalcemia of malignancy (HHM) associated with profound cachexia, increase of serum Ca level, hypophosphatemia, and an enhancement of serum parathyroid-like peptides. In this model system, the effects on cachexia and tumor growth were studied after a series of pulses (3-200) generated by a Candela LFDL/3 equipped pulsed-dye laser with optical fiber guided through a hypodermic needle with a 45 degrees angle bended tip, stuck through the skin of the mouse, and positioned directly below the tumor. The antitumor effect, expressed as a delay of tumor growth, was found to be dependent on number of pulses applied, tumor size, and growth rate (alpha). Treatment of RC-8 with alpha = 0.21 was effective only after 200 pulses combined with a tumor volume smaller than 100 mm3. Under these conditions a growth delay of approximately 8 days was observed, paralleled by delay of animal weight loss (cachexia). Under conditions of a decreased growth rate of RC-8 (alpha = 0.13), the susceptibility toward L-SW was found to be increased, expressed by a suppression of tumor growth after 100 pulses. However, no L-SW-associated delay of cachexia was observed under these latter conditions.