Evaluation of the Toxicity of Total Body Irradation As a Separate Treatment in Preparation for Hematopoietic Cell Transplantation

Myeloablative regimens used for allogeneic or autologous hematopoietic cell transplantation (HCT) may be based on either chemotherapy alone or total body irradiation (TBI). TBI is generally considered highly toxic, however, it is usually combined with high-doses of cyclophosphamide or other cytostatics, which does not allow reliable assessment of its tolerance. In Maria Sklodowska-Curie Cancer Center and Institute of Oncology in Gliwice TBI is used a single treatment in the preparation for the first autologous HCT in patients with multiple myeloma (MM). Second HCT in a tandem procedure is performed after 4 months interval with high-dose melphalan as conditioning. The protocol gives opportunity to separately assess early toxicity of TBI, which is a goal of this study.

The clinical course of 30 patients with MM, aged 58 years (range, 50–66), including 14 men and 16 women was evaluated. The disease status prior to autoHCT was CR (n=9), VGPR (n=7), or PR (n=14). 47% patients were pre-treated with 2 or more lines of chemotherapy and the median number of preceding cycles was 8. TBI was administered at the dose of 12 Gy divided in 3 fractions on days -3, -2, -1. 6 MV X-ray beam was used with lung shielding after 6 Gy and additional irradiation of chest wall using electrons 9–15 MeV to the planned total dose. Peripheral blood was used as a source of stem cells. The incidence of adverse events was assessed using ‘Common Toxicity Criteria v4.03’.

Within 100 days follow-up all patients were alive. Median time to neutrophil >0.5 ×10e9/L and platelet >50 ×10e9/L recovery was 12 days (11–21) and 14 days (9–18), respectively. Patients required the median of 1 (0–3) platelet and 0 (0–6) red blood cell transfusions. The median hospital stay since HCT was 16 days (14–21). The most frequent grade 3 or 4 adverse events were infections (43%), including neutropenic fever (23%). Other severe toxicities were rare. In particular no patient experienced hepatic or renal complications (Table 1).

TBI as a separate treatment is well tolerated and may be safely used for conditioning in a population of patients up to 66 years old. Our observation may potentially be applied to both autologous and allogeneic transplantations.

No relevant conflicts of interest to declare.