[en] PURPOSE: To determine the impact of an external beam boost (EBB) on the outcome, relapse pattern and normal tissue toxicities of patients undergoing total-body irradiation (TBI) prior to bone marrow transplantation (BMT) for relapsed NHL. MATERIALS AND METHODS: Between 1982 and 1994, 299 patients at our institution underwent BMT for relapsed NHL. Patients underwent induction chemotherapy (CT) followed by conditioning with cyclophosphamide and 12 Gy TBI delivered in 6 fractions over 3 days. A total of 77 patients had persistent gross disease, defined as 2 cm or greater, after induction CT and received an EBB prior to BMT (EBB cohort). The median EBB dose was 28.8 Gy (range, 5-63), the median field size was 13 cm² (range, 5-29.4) and the median time from EBB to BMT was 3 weeks (range, 1-20). A total of 222 patients were free of measurable disease or had disease measuring <2cm after CT and did not receive EBB (no-EBB cohort). To assess normal tissue toxicity, patients' simulation films and/or treatment records were reviewed for all 77 patients treated with local EBB and estimates were made of the percentage lung, heart and kidney in the radiation field. RESULTS: A total of 79 of 222 patients (36%) in the no-EBB cohort have relapsed; 33 of 77 patients (43%) in the EBB cohort have relapsed (p=0.28, by Fisher exact test). Median time to relapse after BMT was 54 months for the no-EBB cohort and 38 months for the EBB cohort (p=0.26, by log-rank test). The 3-year actuarial freedom from relapse (deaths in remission censored) was 59% for the no-EBB cohort (90% CI: 52-66%) and 51% for the EBB cohort (90% CI: 40-62%). Data on site of relapse was available for 101 of the 112 relapses (75 no-EBB, 26 EBB). For the no-EBB cohort 33 of 75 relapses (44%) were in sites of prior nodal disease only. For the EBB cohort, 12 of 26 relapses (46%) were in sites of prior nodal disease only, of these, only 6 (23%) were within the EBB treatment field. A total of 26 patients had thoracic irradiation; of these 22 patients had ≥ 25% of one lung, or ≥ 15% of both lungs irradiated. Median EBB dose to the partially irradiated lung was 37.2 Gy (range, 16-63). Seven of the 26 patients receiving thoracic radiation (27%) developed symptomatic radiation pneumonitis. Symptoms have resolved in 4 patients and 3 patients have died of pulmonary complications. A total of 21 patients had abdominal radiation; 9 of these patients had direct kidney irradiation, defined as 10% or greater of total kidney volume. The median EBB dose to the partially treated kidney was 24 Gy. None of the 9 patients who received direct kidney irradiation have developed signs of kidney injury, although 1 of the 21 patients who received abdominal radiation developed a hemolytic uremia syndrome. Six patients had ≥ 50% of the heart irradiated to a median EBB dose of 37.8 Gy (range, 32-47.8). One patient developed a pericardial effusion and constrictive pericarditis after BMT while on IL-2 therapy; this patient died of respiratory causes (included in the pulmonary complication group above). CONCLUSIONS: Patients with recurrent lymphoma with gross residual disease after reinduction chemotherapy (defined as ≥ 2cm in size in this study) have a poor prognosis following BMT. In an attempt to improve the outcome of these patients, an external beam boost was given to sites of residual gross disease prior to BMT. The efficacy of this treatment remains uncertain. Caution must be exercised when using this approach to treat residual thoracic disease, as there is a high risk of associated radiation pneumonitis. However, for patients with resistant thoracic disease, external beam boost followed by BMT may offer the only potential for cure