Effect of localized hyperthermia on TA3Ha tumor transplanted subcutaneously in the tails of mice

Localized hyperthermia (43 degrees) in single or multiple fractions was applied to mouse mammary adenocarcinoma TA3Ha implanted into the s.c. tail tissue of strain A mice. The effects of heat on the growth of local tumors, on the pattern of metastasis, and on the survival periods of the hosts were studied. Hyperthermia was administered by heating the tumor-bearing tails in a water bath. Multiple 30-min hyperthermia treatments at 5- or 7-day intervals controlled local tumor growth better than did a single 30-min treatment or multiple 30-min treatments at 3-day intervals or at intervals longer than 7 days. Heat treatments that produced cytostatic effects on tumors, sparing the normal tissue, had no effect on either the survival of the hosts or the extent of metastasis to the lungs and the lumbar lymph nodes. However, local treatments reduced the frequency of renal lymph node metastasis, indicating that concurrent metastases in different sites may exhibit differential heat sensitivities.