A Minimally Invasive Surgery for Bone Metastases Using the Combination of Photodynamic Therapy and Hyperthermia Treatment

Aims: Cancer patients with bone metastases in their extremities may require surgical intervention to prevent deterioration in their quality of life due to a pathological fracture or severe bone pain. However, curative surgical interventions sometimes have severe complications due to the status of the original cancers. To avoid the decreased quality of life caused by bone metastasis, minimally invasive surgery that avoids additional surgical morbidity is required. We have established two therapeutic treatments for bone metastasis, a photodynamic acridine orange treatment (AOT) and an electronic magnetic hyperthermia treatment (EMHT). The present study investigated the clinical outcomes of combination therapy with EMHT and AOT for patients with bone metastases in their extremities. Methods: The study included 6 patients with 7 bone cancer metastasis locations. For bone metastases, all patients received intraregional tumor excision supported by AOT, in which photodynamic and radiodynamic therapy kills tumor cells during surgery with minimal damage to normal tissues. After the curettage, bone reconstruction was performed by using magnetic materials with calcium phosphate cement. EMHT was repeatedly performed after surgery. In EMHT, tumor cells are killed with an electric magnetic field generator, and bony union is promoted by electronic stimulation. Results: The mean duration of follow-up was 14 months. During the follow-up period, only one patient experienced a local recurrence, and this recurrence occurred 14 months after surgery. Bony union occurred in 4 of 5 cases (80%), and the pain score was significantly reduced after surgery. Conclusions: In the present study, AOT reduced the invasiveness of surgery. EMHT reduced the tumor growth without major complications and promoted bone formation after surgery. Our clinical results confirmed that EMHT and AOT combination therapy for bone metastasis can preserve limb function without local recurrence or bone absorption.