Comparison of tumour blood flow changes induced by step-up and step-down heating

The changes in the blood flow in SCC-VII tumours after step-down and step-up heating (SDH and SUH) were compared. SDH was carried out by initial treatment of tumours in a water bath at 44.5 degrees C for 10 min, immediately followed by heating at 41.5 degrees C for 60 min. For SUH, the sequence of these high- and low-temperature treatments was reversed. Tumour perfusion was evaluated by laser Doppler flowmetry (LDF) at 1, 2, and 24h after finishing the hyperthermia. It was shown that the decrease in the blood flow in tumours was more substantial after SDH than after SUH; in the former case, the drop in LDF values was both faster and larger than in the latter. It is concluded that such a "physiological' component may be involved in the difference in the antitumour effect between SDH and SUH.