No abstract

The use of local hyperthermia to treat cancer of the internal organs has been limited by the difficulty of controlling delivery of heat and limiting the effects to the tumour, but this can be overcome by using laser light transmitted through thin flexible fibres. Laser energy was delivered to tumours through fibres inserted percutaneously through needles directly into the centre of the tumour area. Ultrasound scanning was used to locate the tumour, position the fibres correctly within the tumour, and monitor the development of thermal necrosis in real time during laser exposure and through the subsequent period of healing. Five patients were treated (one with a tumour of the breast, one with a subcutaneous secondary tumour, one with a recurrent pancreatic tumour, and two with secondary tumours in the liver). Tumour necrosis was found on ultrasonography or computed tomography in all, and there were no immediate or delayed complications. In one patient the size of the isolated secondary tumour in the liver had not increased over 10 months, and he subsequently showed no other evidence of residual cancer.To develop this technique careful studies are essential to ensure that in every case the extent of thermal necrosis produced by absorption of the laser light can be matched to the full extent of the tumour being treated and that there is always sufficient adjacent normal tissue to ensure safe healing. These preliminary results suggest that this simple technique can be applied safely and effectively to common tumours in humans; more extensive trials in a range of cancers of solid organs are warranted. IntroductionHyperthermia has for many years been investigated as a way of destroying diseased tissue. The temperatures reached during conventional treatment by hyperthermia induced by microwave or radiofrequency applicators (41-440C) 2 have been used in treating a

Breast MRI is useful in the evaluation of patients with a high clinical suspicion of local recurrence within the irradiated conserved breast.

Summary The palliative management of hepatic metastases remains unsatisfactory. There is a need for a simple non invasive technique which can stop or retard the rate of tumour growth. In principle, Interstitial Laser hyperthermia may fulfil such a role. In experimental studies, this technique produced precise in situ necrosis within solid organs which healed safely. In a pilot feasibility study, we treated ten patients with a total of 18 hepatic metastases on 31 occasions using a percutaneous approach to achieve an overall objective response rate of 44%. The treatment proved simple to perform, was well tolerated and produced radiological evidence of necrosis in small metastases (diameter < 3 cm). However, further research is required before the technique can be regarded as established. Its future role in most cases will be to control the growth of discrete hepatic metastases unsuitable for resection. In instances where the extent of necrosis can be matched accurately to tumour volume, the potential for cure exists.Interstitial Laser Hyperthermia (ILH), an exciting new technique first described in 1983 using the Neodymium: YAG laser (Nd:YAG), is simple both in concept and execution (Bown, 1983). Its basis is the ability to transmit the infra red wavelength of YAG laser light (1064 nm)-an intense energy source, down thin calibre (0.1-0.6 mm) flexible silica or glass fibres with virtually no energy loss. Such small fibre diameters cause negligible tissue damage from their insertion. The light emitting end can be delivered percutaneously into the centre of solid organs (interstitial placement) within the peritoneal cavity using ultrasound guidance with minimal disturbance to the overlying abdominal wall. In contrast to the high powers (50-70 watts) and short exposure times (< 1.0 s) used with the Nd:YAG laser to recanalise obstructing foregut cancers, ILH requires much lower powers (0.5-2.0 watts) with long exposure times (200-1000 s). The laser light is therefore delivered in a more gentle and controlled manner to be absorbed as heat producing a zone of tissue necrosis centred around the fibre tip. The treated area is left in situ to undergo resorption with healing by regeneration and/or fibrosis. In the field of oncology, the prospect of achieving accurate in situ necrosis of malignant tissue simply and atraumatically may obviate, in certain instances, the necessity for surgical excision with its attendant hazards and cost.Experimental work using a single fibre positioned at laparotomy in normal rat liver has produced well defined, reproducible areas of necrosis up to 15 mm in diamter; the diameter being a function of the applied laser power and exposure times (Matthewson et al., 1987). Similar intraoperative studies have also been performed in canine liver using four fibres in juxtaposition fired simultaneously from a single laser (Steger et al., 1988). At 1 week, well defined confluent areas of necrosis up to 3.5 cm in diameter were obtained. These were roughly spherical and centred around the fibres. Such areas...

Multiple four-fibre low-power interstitial laser hyperthermia was performed in the canine liver to establish the parameters with which large areas of thermal necrosis could be made. Using 1.5 W for 670 s (4020 J in total) and a fibre spacing of 1.5 cm, lesions with dimensions of 3.6 x 3.1 x 2.8 cm were achieved in 75 per cent of those attempted. There was no mortality and a low morbidity rate. These lesions could be visualized in both their development and resolution using ultrasonography. Healing occurred by 1 year. Temperatures in the centre of the heated region were 60 degrees C, which is more than enough to cause thermal cell death. There was good correlation between the temperatures recorded, the sonographic changes seen, and the pathological evidence of necrosis. Multiple-fibre low-power interstitial laser hyperthermia performed with ultrasonic guidance may be of use in the treatment of liver tumours.