Tumour pH drop after cryotreatment and enhancement of hyperthermia antitumour effect

Abstract

Our previous study demonstrated a selective drop of pH, PO₂ and blood flow in tumours under induced hyperglycaemia that enhanced the antitumour effect of hyperthermia. However, there are contraindications restricting the use of hyperglycaemia. Cryotreatment, as a method of altering tumour microphysiology similar to hyperglycaemia, was investigated. Guerin carcinoma pH was measured after cryotreatment (-15 to -20°C at the tumour and normal tissue boundary; -110 to -120°C at the cryoinstrument tip). It was determined that tumour pH immediately after complete tumour thawing (10°C) was 6·08 (range 5·5–6·3), by 2 h it was 6·34 (range 6·2–6·4), by 4 h it was 6·42 (range 6·1–6·8) and by 24 h it was 6·54 (range 6·3–6·6). Complete tumour regression (%) and survival of rats with both the tumour regrowth and the partial tumour regression (days) after a single treatment were as follows: control—zero, 28±4; hyperthermia(2450 MHz, 43°C, 60 min)-zero, 30±3; cryotreatment-14, 35±5; cryotreatment+hyperthermia-41, 46±5. It is planned to use combined cryotreatment + hyperthermia in a clinical trial for certain accessible tumours.

Key Words:

• Hyperthermia
• cryotreatment
• tumour pH
• antitumour effect