Comparison between interstitial laser thermotherapy and excision of an adenocarcinoma transplanted into rat liver

Abstract

Summary The aim of this study was to compare interstitial laser thermotherapy with excision of a liver tumour. A dimethylhydrazine-induced adenocarcinoma was transplanted (implanted if not stated otherwise) into the left lateral lobe of the rat liver, and treatment was performed 8 days later. In the main experiment, rats were treated with resection of the tumour-bearing lobe or underwent interstitial laser thermotherapy, which was performed at a steady-state temperature of 460C for 30 min, 3 mm from the tumour margin. The incidence and extent of intraperitoneal spread was smaller after laser thermotherapy than after resection of the tumour-bearing lobe, with no difference in local control. Metastatic spread after resection of the median liver lobe was similar to that observed after sham procedures for thermotherapy or resection, suggesting that the advantage of thermotherapy was not due to a difference in surgical trauma. Additional studies showed that laser thermotherapy reduced intraperitoneal spread when treatment was suboptimal or in a tumour inoculation model and suggested that immunological mechanisms might be involved. It is concluded that interstitial laser thermotherapy reduces spread of liver tumour compared with resection.

Resistance to tumour challenge after tumour laser thermotherapy is associated with a cellular immune response

“…Thermotherapy was carried out with a system consisting of an Nd:YAG laser and a temperature feedback control unit interfaced with the laser, as described in detail elsewhere (Möller et al, , 1997(Möller et al, , 1998 (Figure 1). The laser beam was delivered through a 600-mm flexible bare fibre at a laser output power of 2 W. The bare fibre was placed at right angles into the centre of the tumour, at a depth measuring one-third of the thickness of the liver, including the tumour.…”

“…The treatment characteristics were based on previous studies defining the temperature and duration of treatment needed for complete tumour necrosis, as judged 6 days after treatment (Möller et al, , 1997(Möller et al, , 1998. Interstitial laser thermotherapy of normal liver was performed in the same way, using the distance between the laser fibre and thermistor probe found in rats with tumours.…”

“…Using a model of adenocarcinoma implanted into rat liver, we reported that ILT gave results that were superior to those of surgical resection of the tumour-bearing liver lobe (Möller et al, 1998). The efficacy of local tumour removal was similar, but the ILT method was associated with less extrahepatic spread.…”

“…The reason why local excision alone may not be sufficient for cure is the risk for occult disseminated disease and, also, the risk for local recurrence. Surgery is known to induce immunosuppression and the release of growth factors that may stimulate growth of residual tumour (discussed in Möller et al, 1998). The reason why systemic therapy like chemotherapy or immunotherapy is likely to be insufficient as the sole treatment is their relative inefficacy for solid tumours and the fact that clinical tumour burdens are large.…”

“…As for immunotherapy, possible success appears to depend on combination with procedures that give efficient tumour killing and antigen exposure. Heating of tumour cells with interstitial laser thermotherapy (ILT) is interesting in this respect, since it can accomplish total local tumour destruction by tumour necrosis at the same time as it induces an immunological response against the tumour (Möller et al, 1998;Tranberg et al, 2002).…”