Purpose: To estimate the maximum tolerated dose of hyperfractionated total marrow irradiation (TMI) as a second consolidation after high-dose chemotherapy with autologous or syngeneic blood stem cell transfusion for patients with bone/bone marrow-based malignant disease.
Patients and methods: Fifty-seven patients aged 3-65 years (median, 45 years), including 21 with multiple myeloma, 24 with breast cancer, 10 with sarcoma, and 2 with lymphoma, were treated with 1.5 Gy administered twice daily to a total dose of 12 Gy (n = 27), 13.5 Gy (n = 12), and 15 Gy (n = 18). Median time between the 2 transplants was 105 days (range, 63-162 days).
Results: All patients engrafted neutrophils (median, Day 11; range, Day 9-23) and became platelet independent (median, Day 9; range, Day 7-36). There were 5 cases of Grade 3-4 regimen-related pulmonary toxicity, 1 at 12 Gy, and 4 at 15 Gy. Complete responses, partial responses, and stabilizations were achieved in 33%, 26%, and 41% of patients, respectively. Kaplan-Meier estimates of 5-year progression-free survival and overall survival for 56 evaluable patients are 24% and 36%, respectively. Median time of follow-up among survivors was 96 months (range, 77-136 months).
Conclusion: Total marrow irradiation as a second myeloablative therapy is feasible. The estimated maximum tolerated dose for TMI in a tandem transplant setting was 13.5 Gy. Because 20% of patients are surviving at 8 years free of disease, further studies of TMI are warranted.