The role of local radiation therapy for mediastinal disease in adults with T-cell lymphoblastic lymphoma

BACKGROUND. Mediastinal recurrence remains the most common cause of failure in patients with mediastinal T-cell lymphoblastic lymphoma (LBL). The role of mediastinal radiation therapy in improving local disease control and overall prognosis is not well-known with modern intensive chemotherapy. The objective of this study was to investigate the role of mediastinal radiation therapy in patients who achieve a complete response (CR) to chemotherapy. METHODS. The authors reviewed 47 patients with mediastinal T-cell LBL with or without bone marrow (BM) involvement who presented between 1980 and 1998. The median patient age was 25 years, and 33 patients (70%) were males. BM involvement was present in 16 patients (34%), 5 patients (11%) were in leukemic phase, lymph node involvement in was present 23 patients (49%), hepatosplenomegaly was present in 4 patients (9%), and pleural effusions were present in 22 patients (45%). The initial chemotherapy regimens were fractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (hyper-CVAD) in 23 patients; cyclophosphamide, vincristine, doxorubicin, and dexamethasone in 9 patients; vincristine, doxorubicin, and dexamethasone in 4 patients; cyclophosphamide, doxorubicin, vincristine, and prednisone in 4 patients; and other in 7 patients. Forty-three patients achieved a CR to chemotherapy and were the subject of this analysis. Nineteen of those patients received adjuvant mediastinal radiation therapy at a dose ranging from 26 grays (Gy) to 39 Gy. RESULTS. There was no difference in patient characteristics between the 19 patients who were treated with mediastinal radiation therapy and the 24 patients who did not receive mediastinal radiation therapy. The median follow-up for all 43 patients was 43 months. The 5-year overall survival (OS) rate was 66%, and the freedom from progression (FFP) rate was 64%. None of 19 patients who received radiation therapy experienced a mediastinal recurrence compared with 8 of 24 patients who did not receive radiation therapy and experienced a mediastinal recurrence. Patients who were treated with mediastinal radiation therapy had a significantly better mediastinal FFP rate (P = 0.01), but the differences in overall FFP and OS rates were not significant (P = 0.14 and P = 0.25, respectively). The effectiveness of the hyper-CVAD regimen seemed to underscore the role of mediastinal radiation therapy; only 2 patients experienced a recurrence among 16 patients who received mediastinal radiation therapy, both outside the mediastinum. This compared with two patients who experienced a recurrence among six patients who did not receive mediastinal radiation therapy, both in the mediastinum. CONCLUSIONS. Local radiation therapy significantly decreased the risk of mediastinal recurrence in adult patients with mediastinal T-cell lymphoblastic lymphoma. The benefit of adjuvant radiation therapy was particularly evident in patients treated with more intensive chemotherapy regimens.