Some practical considerations for the use of localized hyperthermia in the treatment of cancer.

Practical considerations in the selection and administration of microwave and RF induced hyperthermia in the treatment of various tumors are discussed. A thorough knowledge of the thermal properties of the tumor and its environment is required for the establishment of an effective therapeutic regimen. Examples of clinical observations illustrate the patients' general tolerance to the therapy and highlight the problems presented by some special cases. Possible ways of avoiding adverse effects during localized microwave induce heating of superficial tumors and RF heating of deep seated tumors are described.

Therapeutic potential of conformal applicators for induction of hyperthermia.

One of the basic requirements for effective use of hyperthermia in treatment of cancer is the delivery of uniform heat to specific volumes of tissues and maintenance of the optimal temperature for an appropriate period of time. Preliminary results of temperature distribution in volumes of tissue placed between two conformal applicators energized at 2.45 GHz are presented. The applicators consist of a jointed-circuit antenna array comprising a multiplicity of dipoles backed by a metal cavity filled with a powder of high dielectric constant, and separated from the treatment area by a "beanbag" filled with the same powder. Uniform heating could be achieved in a tissue mass confined between two applicators placed 5 cm apart.

Effects of microwave-induced local hyperthermia on mammary adenocarcinoma in C3H mice.

Microwave-induced hyperthermia was focused locally upon mammary adenocarcinoma implanted in C3H mice when the tumor reached 6 mm in diameter. In 54 treated mice, all tumors diminished in size after the first exposure (43 degrees, 45 min) and disappeared completely following the second treatment. No other effects from heat application were apparent. All the mice in the microwave-treated group survived the whole period of observation (4 months) without any evidence of tumor, while 18 nontreated controls died within 4 weeks after inoculation.

The effect of dead cells on the activity of actinomycin D against mouse sarcoma 180 ascites.

It has been demonstrated that cells killed by heat or irradiation have four times greater affinity for actinomycin D (AMD) than do viable tumor cells. By using a double labeling technique, we were able to show that, with increasing amounts of AMD bound in cells, the incorporation of RNA precursors is proportionally decreased. However, in the presence of nonviable cells or of native DNA, the AMD-induced inhibition of [3H]uridine incorporation is markedly reduced. This reduction does not occur if DNase is added to the system. The accumulation of dead cells in the tumor vicinity during the natural course of tumor growth or therapy must be taken into consideration in planning therapeutic regimens. We suggest that, in combined chemo- and radiotherapy, increased effectiveness of AMD may be obtained by its use prior to irradiation, thereby assuring its direct access to the tumor cells. The addition of DNase could eliminate or greatly diminish the dead cell competition for the drug.