Is Limb Salvage With Microwave-induced Hyperthermia Better Than Amputation for Osteosarcoma of the Distal Tibia?

Amputation has been the standard surgical treatment for distal tibia osteosarcoma owing to its unique anatomic features. Preliminary research suggested that microwave-induced hyperthermia may have a role in treating osteosarcoma in some locations of the body (such as the pelvis), but to our knowledge, no comparative study has evaluated its efficacy in a difficult-to-treat location like the distal tibia.

Does microwave-induced hyperthermia result in (1) improved survival, (2) decreased local recurrence, (3) improved Musculoskeletal Tumor Society (MSTS) scores, or (4) fewer complications than amputation in patients with a distal tibial osteosarcoma?

Between 2000 and 2015, we treated 79 patients for a distal tibia osteosarcoma without metastases. Of those, 52 were treated with microwave-induced hyperthermia, and 27 with amputation. Patients were considered eligible for microwave-induced hyperthermia if they had an at least 20-mm available distance from the tumor edge to the articular surface, good clinical and imaging response to neoadjuvant chemotherapy, and no pathologic fracture. Patients not meeting these indications were treated with amputation. In addition, if neither the posterior tibial artery nor the dorsalis pedis artery was salvageable, the patients were treated with amputation and were not included in any group in this study. A total of 13 other patients were treated with conventional limb-salvage resections and reconstructions (at the request of the patient, based on patient preference) and were not included in this study. All 79 patients in this retrospective study were available for followup at a minimum of 12 months (mean followup in the hyperthermia group, 79 months, range 12-158 months; mean followup in the amputation group, 95 months, range, 15-142 months). With the numbers available, the groups were no different in terms of sex, age, tumor grade, tumor stage, or tumor size. All statistical tests were two-sided, and a probability less than 0.05 was considered statistically significant. Survival to death was evaluated using Kaplan-Meier analysis. Complications were recorded from the patients' files and graded using the classification of surgical complications described by Dindo et al.

In the limb-salvage group, Kaplan Meier survival at 6 years was 80% (95% CI, 63%-90%), and this was not different with the numbers available from survivorship in the amputation group at 6 years (70%; 95% CI, 37%-90%; p = 0.301).With the numbers available, we found no difference in local recurrence (six versus 0; p = 0.066). However mean ± SD MSTS functional scores were higher in patients who had microwave-induced hyperthermia compared with those who had amputations (85% ± 6% versus 66% ± 5%; p = 0.008).With the numbers available, we found no difference in the proportion of patients experiencing complications between the two groups (six of 52 [12%] versus three of 27 [11%]; p = 0.954).

We were encouraged to find no early differences in survival, local recurrence, or serious complications between microwave-induced hyperthermia and amputation, and a functional advantage in favor of microwave-induced hyperthermia. However, these findings should be replicated in larger studies with longer mean duration of followup, and in studies that compare microwave-induced hyperthermia with conventional limb-sparing approaches.

Level III, therapeutic study.