Interstitial laser thermotherapy of adenocarcinoma transplanted into rat liver

To examine the effect of different temperatures and exposure times in interstitial laser thermotherapy.

Controlled laboratory study.

University hospital, Sweden.

48 male Wistar FU rats with dimethylhydrazine-induced adenocarcinoma transplanted into the liver.

Treatment was given with an Nd:YAG laser and a feedback system for temperature regulation. Light was delivered into the centre of the tumour and the feedback thermistor probe was placed 3 mm from the tumour margin. Rats were treated at steady-state temperatures at the feedback thermistor of 43, 46, or 50 degrees C for 30 minutes, and at a steady-state temperature of 46 degrees C at the feedback thermistor also for 10 and 20 minutes.

Tumour control as assessed 6 days after treatment using light microscopical examination including immunohistochemical determination of bromodeoxyuridine (BrdU) incorporation into DNA as a measure of cell viability.

Complete tumour necrosis was achieved in all rats treated for 30 minutes, in 6/8 rats treated for 10 minutes and in 6/8 rats treated for 20 minutes at 46 degrees C. During steady-state thermotherapy, temperatures at the tumour margin were about 11 degrees higher than at the feedback thermistor (range 54-61 degrees C). The surrounding liver tissue also became necrotic so that the total necrosis volume exceeded the pretreatment tumour volume.

Interstitial laser thermotherapy at temperatures ranging from 54-61 degrees C at the tumour margin ensures total necrosis of a transplanted rat liver carcinoma provided that treatment is given for 30 minutes.