Radiation therapy for consolidation of metastatic or recurrent sarcomas in children treated with intensive chemotherapy and stem cell rescue. A feasibility study

Purpose: To assess the role of consolidative radiation therapy (CRT) in conjunction with myeloablative therapy with or without total body irradiation (TBI) in children and young adults with metastatic or recurrent sarcoma. Methods and Materials: Twenty-one pediatric sarcoma patients with metastatic (10) or recurrent (11) disease were entered on a prospective feasibility study of intensive myeloablative therapy with or without TBI. Median patient age was 17.8 years (range, 9.4-24.7 years). Primary histologies included Ewing's (12), PNET (3), and other soft tissue sarcomas (6). Twenty patients received induction chemotherapy. Myeloablative therapy consisted of TBI in 11 patients with either high dose melphalan/etoposide (9) or high dose cytoxan/thiotepa (2). TBI consisted of 12 Gy in 2 Gy fractions delivered twice daily over 3 days. Ten patients received high dose chemotherapy alone, either with thiotepa/carboplatinum/etoposide (8) or cytoxan/carboplatinum (2). Myeloablative therapy was followed by autologous stem cell rescue (ASCR) 24 to 48 hours after completing chemotherapy. Fourteen patients (67%) received CRT either prior to (5) or following (9) myeloablative therapy. Median CRT dose was 37.2 Gy (range, 20-60). Fifty-one disease sites were present prior to myeloablative therapy. Twelve (24%) were bulky (> 8 cm) and 18 (35%) underwent surgical debulking. The median follow-up of surviving patients was 15 months (range, 8-20) with 25% of patients having been followed for more than 20 months. Results: The 3-year actuarial disease-free (DFS) and overall survival (OS) rates for the entire group were 36% and 27%, respectively. Following myeloablative treatment, responses were: 11 complete, 6 partial, 1 stable, and 3 progressive disease. Sixteen patients (71%) have relapsed. The most common site of relapse was the lung (13). Of the 51 disease sites present prior to myeloablative therapy, 36 sites (71%) were amenable to CRT. Nonamenable sites were: multiple lung metastases (13) and bone marrow (2). Twenty-six amenable sites (51%) received CRT either prior to (14) or following (12) ASCR. Amenable sites treated with CRT had a better 3- year actuarial local control (80 vs 37%) (p = 0.0065) than amenable sites not treated with CRT. Factors associated with improved disease-free survival (DFS) in univariate analysis were induction chemotherapy response (p = 0.002) and extent of surgical resection (p = 0.045). There was a trend toward improved DFS on univariate analysis with the use of TBI as part of myeloablative therapy (p = 0.07). The one factor associated with improved OS on univariate analysis was induction chemotherapy response (p = 0.007). Multivariate analysis revealed that induction chemotherapy response is the only factor that remains significant for DFS (p = 0.032) as well as for OS (p = 0.017). Patients with complete response to induction therapy had 40% probability of survival versus all other patients who had 10% survival (p = 0.05). Conclusion: Consolidative radiotherapy is feasible in primary metastatic or recurrent pediatric sarcoma patients treated with myeloablative therapy with or without TBI. CRT to sites amenable to irradiation provided an improved 3-year actuarial local control than that seen in sites amenable to CRT that did not undergo radiotherapy. There was a trend for improved DFS with the use of TBI. Improved DFS and OS can be predicted by response to induction therapy. This intensive regimen may improve the cure rate of advanced pediatric sarcomas in select patients.