Biological modeling of thermoradiotherapy

Standard treatment for advanced stage cervical cancer is chemoradiotherapy. When there is a contraindication for chemotherapy, thermoradiotherapy is a good alternative. Thermoradiotherapy combines radiotherapy with hyperthermia, a treatment in which the tumor is heated to fever temperatures (40 – 42 °C). Hyperthermia is known to make tumors more sensitive to irradiation, while having a limited effect on normal tissue.
Hyperthermia treatment plans are optimized to heat the tumor as much as possible, whilst not exceeding temperature limits in normal tissues. Similarly, radiotherapy treatment plans are optimized to selectively irradiate tumors. However, creating separate treatment plans does not account for the interaction between the two treatments.
In this thesis, biological models have been developed to evaluate the expected biological effect of combined radiotherapy and hyperthermia treatments. These biological models have been implemented in software that can evaluate the quality of such combined treatment plans. The software can, for example, be used to evaluate the potential added benefit of hyperthermia for individual patients, or to improve the treatment schedule for existing patient groups.
The optimal time interval between radiotherapy and hyperthermia for the treatment of cervical cancer patients has long been a subject of debate. Using the biological modeling software, treatments with various time intervals were modeled for cervical cancer patients, and short time intervals between radiotherapy and hyperthermia were found to be optimal. A retrospective clinical study, also part of this thesis, confirms that finding. Ensuring such short time intervals may improve the treatment outcome.