Clinical data for 15 patients with a recurrent bone tumor are summarized (Table 1). The pathological types of recurrent tumors included 1 case of osteoid osteoma, 6 cases of giant cell tumors of bone, 2 cases of chondroblastoma, 2 cases of osteosarcoma, 1 case of undifferentiated sarcoma, and 3 cases of bone metastasis. The series included 7 men and 8 women, with a median age of 27.5 y (range: 12–69 y). The median follow-up period was 27 months (range: 11–92 months). Microwave ablation was conducted on all patients in the following locations: femora, 9 (60.0%); tibiae, 3 (20.0%); humeri, 2 (13.3%); and radius, 1 (6.7%).
Surgical treatments
Two patients—one with recurrent osteoid osteoma (Patient 1) and another with recurrent renal carcinoma metastasis (Patient 15)—underwent percutaneous microwave ablation for the tumor; meanwhile, the remaining 13 patients underwent adjuvant intraoperative microwave ablation. In the percutaneous microwave ablation, the tumor lesion was accurately located, and the puncture path was planned under CT guidance. A coaxial technique was used to guide the insertion of a 15G disposable microwave ablation antenna (2 mm in diameter, 150 mm in length, 2450 MHz generator, ECO -100A1 from Nanjing ECO Microwave System Co., Ltd.) to the tumor center. Patient 1, a 13-year-old boy with osteoid osteoma in the left femoral diaphysis, reexperienced pain symptoms. The boy underwent percutaneous radiofrequency ablation of the tumor 8 months before the aforementioned symptoms. Ablation with microwave output power 40 W was performed on recurrent osteoid osteoma for 2 min under local anesthesia and nerve block anesthesia. Patient 15, a 63-year-old male patient with renal carcinoma metastasis in the proximal humerus, reexperienced pain symptoms in his left upper arm. The patient underwent tumor curettage followed by cementation and internal fixation 6 months ago. Pazopanib treatment failed to achieve tumor control. Imaging revealed new osteolytic lesions with a diameter of about 2 cm in the internal fixation area. The existence of previous internal fixation provided good bone stability; thus, the recurrent humoral metastasis was treated by ablation with a microwave output power of 50 W for 4 min under local anesthesia (Fig. 1).
Thirteen patients with local recurrent bone tumors underwent intraoperative microwave ablation before curettage or resection. The microwave equipment was the same as the aforementioned device. The microwave ablation power and ablation time were selected depending on the lesion location and size. When the microwave ablation area was close to the articular surface, intra-articular ice saline perfusion was employed. Six patients (Patients 2 to 7) with giant cell tumors of bone and 2 patients (Patients 8 and 9) with chondroblastoma underwent tumor curettage and bone grafting or cementation in the past 2 years. After recurrent tumor microwave ablation and curettage, 6 patients with giant cell tumors of bone received cementation (Fig. 2), and 2 patients with chondroblastoma was treated with allograft. The bone graft and cement in the primary treatment was totally removed before further curettage. Three patients (Patients 10, 11, and 12) with recurrent primary malignant bone tumors received intraoperative microwave ablation before resection. Patient 10 developed osteosarcoma recurrence and lung metastasis 3 y after tumor bone inactivation combined with prosthesis reconstruction (Fig. 3). Patient 11, who underwent osteosarcoma resection and mega-prosthesis reconstruction, had local recurrence and lung metastasis 9 months after surgery. Patient 12, who received undifferentiated sarcoma resection, experienced local recurrence and lung metastasis 6 y after surgery. She underwent microwave ablation, curettage, and internal fixation of a femoral tumor. Two patients (Patients 13 and 14) with recurrent bone metastasis were treated with intraoperative microwave ablation before curettage. Patient 13 had a left thigh tumor recurrence, left tibial metastasis, and multiple-lymph-node metastasis 19 months after resection of left thigh liposarcoma. Patient 14 had right tibial tumor metastasis 11 months after inactivation and replantation of osteosarcoma in the distal right femur.
Regarding the 2 patients who received percutaneous microwave ablation, for Patient 1, pain disappeared and the tumor was cured; for Patient 15, pain was relieved, and the VAS score was reduced from 9 to 2. Six patients (Patients 2 to 7) with recurrence after curettage of giant cell tumors of the bone regained local tumor control and retained their joints. One patient (Patient 7) received continuous denosumab treatment for lung metastasis. Two patients (Patients 8 and 9) with recurrent chondroblastoma regained local tumor control and retained their joints without other interventions in the follow-up. Four patients (Patients 10, 11, 13, and 14) with malignant recurrent bone tumors and multiple metastases achieved good local tumor treatment within the survival time. Patient 12 with a malignant recurrent bone tumor achieved good local tumor control and stable lung lesion in the follow-up.
In this series, 1 patient (Patient 7) with a giant cell tumor of bone and 6 patients (Patients 10 to 15) with malignant bone tumors had lung metastases or multiple metastases. Patients 7, 12, and 15 survived despite having tumors. The other 4 patients died of tumor metastasis 11–15 months after the operation. The mean MSTS score for limb function 6 months after the operation in 15 patients was 24.1 (range: 17–30). The limb function of the patients with benign tumors (25–30) was better than those of patients with malignant tumors (17–22) because of the differences in previous operations. No perioperative complications were found in these 15 patients.