P3B035: Practice Patterns in Palliative Site-directed Local Therapy in Pediatric Oncology: A Report from the Pediatric Surgical Oncology Research Collaborative

Background: End-stage pediatric solid tumor patients with recurrent, metastatic, or surgically inaccessible tumors require nonsurgical options for site-directed local control. Access to palliative ablation strategies may improve quality of life and extend survival. We investigated the practice of palliative ablation strategies in pediatric solid tumor patients, including toxicities and reasons for selecting palliative ablation.

Methods: This was a multi-center, retrospective cohort study of children and young adults under 39 years of age with a solid tumor diagnosis ineligible for surgical local control due to anatomic location or palliative only treatment intent. Treatment modalities included cryoablation, radiofrequency ablation (RFA), microwave ablation (MWA), and stereotactic body radiotherapy (SBRT). Treatment sites were limited to pulmonary, hepatic, and bony sites. Patients were treated between 2010 – 2020 at 1 of 5 institutions participating in the Pediatric Surgical Oncology Research Collaborative (PSORC). Demographic, histologic, and clinical data were obtained. Descriptive statistics were generated for numeric variables. Assessment of patient reasons for choosing ablative strategies were qualitatively assessed by chart review.

Results: 66 patients underwent 89 separate ablative procedures for 132 lesions. More than ten histologies were represented, the most common of which were Ewing sarcoma (n = 15 patients), osteosarcoma (n = 13 patients), and rhabdomyosarcoma (n = 9 patients). Techniques included cryoablation (n = 9 procedures/16 lesions), RFA (n = 4 procedures/5 lesions), MWA (n = 5 procedures/12 lesions), and SBRT (n = 68 procedures/99 lesions). Grade 3 or higher toxicities included pain requiring IV medication in cryoablation (3/12 procedures), RFA (1/4 procedures), and MWA (2/5 procedures), bleeding in MWA (2/5 procedures), and skin burns requiring intervention in SBRT (1/68 procedures). Patients were generally hospitalized after percutaneous ablation (19/21 cryoablation, RFA, and MWA procedures) but the hospital stay was short (mean/SD 1 +/- 4 days). Only 4 patients who were already hospitalized experienced hospitalization extension due to ablative procedure. The primary reason for pursuing ablative measures included treatment of unresectable disease either due to surgical inaccessibility or metastasis (n = 31), symptom relief, either pain or mass effect (n = 25), specific patient QOL concerns unrelated to pain or life prolongation (n = 5), and physiologic instability for otherwise resectable disease (n = 4). All patients undergoing treatment for symptom relief received SBRT.

Conclusion: In these patients undergoing percutaneous ablation or SBRT for palliation, ablation strategies were well tolerated. Toxicities were manageable and inpatient admission/hospitalization extension was minimal. Further research is needed to determine extent of prolongation of life or symptom relief after ablation strategies, utility of percutaneous strategies in relieving symptomatology compared to SBRT, and patient and family satisfaction with ablative strategies. Additionally, given the low number of institutions using these strategies in palliative oncology, an understanding of institutional reluctance to employ these strategies is desirable.