Temperature Profiles and Oxygenation Status in Human Skin and Subcutis Upon Thermography-Controlled wIRA-Hyperthermia

Efficacy of wIRA immediately followed by hypofractionated radiation in the treatment of locally recurrent breast cancer and other superficial tumors is documented. A prerequisite for the additive and synergistic radiosensitizing properties of hyperthermia is the assessment of resulting temperatures of tumors and normal tissues. To assess the role of hyperthermia in reversing tumor hypoxia through its effects on local blood flow, oxygen profiles in skin, subcutis, and superficial tumors have been additionally assessed during mild hyperthermia (39–43 °C). Upon wIRA-exposure, skin surface temperatures increased from 35 to 41.6 °C within 5–12 min. Maximum temperatures of 42 °C were found in subepidermal regions, with a steady decline in deeper layers reaching 40.1 °C at a depth of 20 mm. Heating was accompanied by increases in tissue oxygen tensions. Effective hyperthermia levels (≥ 39 °C) were established in depths up to 25 mm. Following wIRA exposure, tissue temperatures returned to pretreatment levels within a few minutes, with the decay time depending on tissue depths, while pO values remained on therapeutical levels for 30–60 min postheat, outlasting the period needed for subsequent radiotherapy. Monitoring in the upper dermis layer of skin and recurrent breast cancers confirmed the improved O status during wIRA exposure and outlasted the time needed for subsequent radiotherapy.