Feasibility of helical tomotherapy for debulking irradiation before stem cell transplantation in malignant lymphoma

Preliminary clinical experience has suggested that radiation therapy (RT) may be effectively incorporated into conditioning therapy before transplant for patients with refractory/relapsed malignant lymphoma. We investigated the feasibility of debulking selective lymph node irradiation before autologous and/or allogeneic stem cell transplantation (SCT) using helical tomotherapy (HT).

Six consecutive patients with refractory malignant lymphoma were referred to our institution for salvage HT before SCT. All patients had been previously heavily treated but had bulky residual tumor despite chemotherapy (CT) intensification. Two patients had received previous radiation therapy. HT delivered 30-40 Gy in the involved fields (IF), using 6 MV photons, 2 Gy per daily fraction. Total duration of treatment was 28 to 35 days.

Using HT, doses to critical organs (heart, lungs, esophagus, and parotids) were significantly decreased and highly conformational irradiation could be delivered to all clinical target volumes. HT delivery was technically possible, even in patients with lesions extremely difficult to irradiate in other conditions or in patients with previous radiation therapy. No Grade 2 or higher toxicity occurred. Four months after the end of HT, 5 patients experienced complete clinical, radiologic, and metabolic response and were subsequently referred for SCT.

By more effectively sparing critical organs, HT may contribute to improving the tolerance of debulking irradiation before allograft. Quality of life may be preserved, and doses to the heart may be decreased. This is particularly relevant in heavily treated patients who are at risk for subsequent heart disease. These preliminary results require further prospective assessment.