Hyperthermia and cancer

Histopathological observations in the canine prostate treated by local microwave hyperthermia

A large series of repeated experiments were performed applying localized microwave hyperthermia to the prostate in dogs using a new water-cooled skirt-type antenna [1], operating at 915 MHz, as part of a new hyperthermia apparatus being developed for the treatment of the prostate in humans. The prostate gland of 20 male dogs was heated repeatedly under general anesthesia, at temperatures between 40 degrees C and 47 degrees C, and for different lengths of time up to 10 h. The prostate and other tissues were evaluated histopathologically following treatments. Invariably, all treatments by hyperthermia of the prostate caused a mononuclear inflammatory infiltration in the interstitium and polymorphonuclear infiltration in the glandular elements. Permanent tissue damage was found to be time-and temperature-dependent. Heating at 42.5 degrees C (+/- 0.5 degrees 5C) for up to 1.5 h was found to be harmless and could be safely repeated with our equipment. This study was part of a preclinical evaluation of a new antenna and apparatus.

Effects of temperature on protein turnover in isolated rat skeletal muscle

To understand the net loss of muscle protein during fever and the possible changes in body protein balance with hyperthermia, we investigated the influence of temperature on protein synthesis and degradation in rat skeletal muscles. In the incubated soleus, extensor digitorum longus, or diaphragm, net protein degradation increased by about 11%/degrees C between 33 and 42 degrees C. This loss of muscle protein resulted from an increase in protein degradation (172% between 33 and 42 degrees C). By contrast, protein synthesis increased by only 25% between 33 and 39 degrees C and fell markedly by 42 degrees C. Unlike muscle, in isolated rat hepatocytes, protein breakdown did not increase significantly between 36 and 39 degrees C. The stimulation of protein degradation between 36 and 39 degrees C was not reduced by leupeptin or Ep-475, which inhibit lysosomal thiol proteases and reduce net protein degradation in the incubated muscles. Prostaglandin E2 (PGE2) has been implicated in the accelerated muscle proteolysis during fever. However, PGE2 release by muscles was unchanged between 33 and 42 degrees C, and inhibition of PGE2 synthesis by indomethacin did not reduce the stimulation of proteolysis at 40 degrees C. This catabolic effect of increased temperature may contribute to the negative nitrogen balance during fever.

Effects of systemic hyperthermia and intrahepatic infusion with 5-fluorouracil

Potential hepatotoxicity from systemic hyperthermia (43 degrees C) +/- simultaneous hepatic artery infusion with 5-FU was evaluated in an animal model. Twenty-two dogs had aorta-vena caval shunts (8 mm Dacron grafts) placed, and 10 of these dogs had silastic catheters inserted in their hepatic arteries. Two weeks later, Group I (n = 8) was heated to 43 degrees C for one hour (distal esophageal + intrahepatic temperature) using the shunts and blood-heat exchangers; Group II (n = 6) was heated to 43 degrees C for one hour with simultaneous intrahepatic infusion of 5-FU (10 mg/kg); Group III (n = 8) was shamheated (37 degrees C) and underwent a one hour intrahepatic infusion with 5-FU (10 mg/kg). Serum alkaline phosphatase, SGOT, SPGT (IU/ml) and bilirubin were measured, and liver biopsies were obtained at 0 and 1 hour, at one and seven days. Mean SGOT levels increased significantly (P less than 0.05) in Group II from 19 +/- 2 to 31 +/- 6 and 63 +/- 18 at one hour and one day; these levels rose slightly in Group I from 31 +/- 5 to 40 +/- 8 and 47 +/- 8 at one hour and one day. Hepatocellular enzyme levels returned to normal at seven days in both groups. Mean SGOT and SGPT levels remained similar in Group III at all time periods. No significant differences in mean serum alkaline phosphatase or bilirubin levels were noted. There was no histologic evidence of hepatocellular necrosis at any time period. Survival was 6/8, 5/6 and 8/8 dogs in Groups I, II, and III, respectively. Systemic hyperthermia to 43 degrees C for one hour in dogs does not adversely affect serum hepatic enzymes or cell structure; reversible serum hepatic enzyme changes occurred when hyperthermia was combined with hepatic artery infusion with 5-FU.

New surgical approaches to pancreatic cancer

Surgery as the best means to careful staging is stressed, in spite of many other methods of staging. Especially in those instances where resection is remotely possible it is proposed that, if possible, surgery should be done in centers specializing in this type of operation. A final opinion on the use of extended pancreatectomy awaits additional data. It is stressed that the surgeon should be fully aware of combined modality programs for treating pancreatic cancer and that new surgical techniques be considered as their proper employment demands. Finally, possible new techniques, such as intraoperative photoradiation using a laser and hematoporphyrin, intraoperative radiation therapy and heat, and the use of microwave-induced hyperthermia are discussed. The surgeon may well find that what is new in surgical treatment of cancer of the pancreas lies in a combined modality approach, primarily using intraoperative therapy.