Electrochemotherapy of spinal metastasis using transpedicular approach: a preclinical safety animal study.

Background: Electrochemotherapy (ECT) of vertebral metastasis is a new treatment option for metastasis that is not accessible to thermal ablation or radiotherapy. A numerical feasibility study has investigated the transpedicular approach for electrode insertion. We conducted a preclinical study to assess its safety.

Methods: Histologic examination of the spinal cord was performed in 12 consecutive pigs treated with ECT at three consecutive levels (T11, T12, and L1) to evaluate any cellular or vascular damage. Pigs of group A (n = 6) had an intraoperative neuromonitoring immediately for 1 h after ECT and then were euthanized. Pain and clinical symptoms were daily evaluated for group B (n = 3) and group C (n = 3) until day-3 and day-30, respectively.

Results: At gross pathology, no apoptosis, no vascular/thrombosis or hemorrhagic focus was observed in any pig. Motor-evoked potential responses of the lower limbs were transiently lost in response in 5 of the 6 pigs, but complete recovery always occurred within 30 min. Clinical examination (groups B and C) revealed no symptoms during the follow-up. Pigs were all able to walk normally, without weakness or paralysis of the lower extremities. No urinary/fecal retention or incontinence was observed, nor any sign of pain.

Conclusion: Our results confirm that the insertion of electrodes through the pedicles is safe for the ECT of vertebral metastases. Further studies are needed to evaluate the safety profile of ECT of vertebral metastases invading the cortical and epidural fat, which represents a privileged pathway for the electric field between the electrodes.

Relevance statement: Electrochemotherapy of vertebral metastases should be performed using a transpedicular approach for the insertion of electrodes, without definitive sequelae at the spinal cord level.

Key points: Electrochemotherapy is a new treatment for vertebral metastases not accessible to radiotherapy, but it could result in spinal cord injury related to electrical trauma. In a swine model, the transpedicular approach has demonstrated no definitive sequelae at intraoperative neuromonitoring and during clinical follow-up. Electrochemotherapy should be performed using a transpedicular approach to avoid spinal cord damage.