Simultaneous radiotherapy and superficial hyperthermia for high-risk breast carcinoma: A randomised comparison of treatment sequelae in heated versus non-heated sectors of the chest wall hyperthermia

Purpose: In vitro data demonstrate that heat-induced radiosensitisation is maximised if hyperthermia and radiotherapy are given simultaneously, with the radiation fraction delivered midway through a hyperthermia session, rather than sequentially. The long-term normal tissue toxicity of full-dose simultaneous thermoradiotherapy is unknown. Materials and methods: Patients with locally advanced breast cancer (T3, T4 or more than three involved nodes or local recurrence), no prior radiotherapy, received between four and eight sessions of simultaneous thermoradiotherapy. Hyperthermia always included the primary tumour site. In addition an electively heated sector (EHS) was included. The EHS was randomised to either medial or lateral to the tumour site, with the other side an irradiated but unheated control. As per our usual practice, patients received surgery and/or chemotherapy prior to radiotherapy. Radiation doses were 4650Gy followed by a boost of ≤16Gy at 1.82Gy per fraction. EHS and control sectors received the same dose. Results: A total of 57 evaluable cases with average follow-up of 79 months experienced two local and two nodal recurrences. There was no significant difference in ≥grade 2 toxicity for heated versus control sectors (LR 0.78, p0.38) with no relationship between number of hyperthermia sessions and toxicity (LR 2.90, p0.09). Conclusions: Simultaneous full-dose thermoradiotherapy for breast cancer is feasible and well tolerated, with no significant difference in late toxicity between electively heated and unheated control sectors. All patients had hyperthermia to the primary tumour site with excellent local control.