Dr. Shikha Halder
Director & Senior Consultant
Radiation Oncology
BLK Super Speciality
Hospital, New Delhi

Total Body Irradiation (TBI) is an important component of Haematopoietic Stem Cell Transplant (HSCT), with the goal of eradicating residual malignant cells and modulating the immune system of the transplant recipient. TBI is advantageous because biologic effects can be exerted uniformly, without sparing of “sanctuary” sites like the nervous system or testes and without interference from metabolic or resistance processes. It also reduces graft versus host disease.

TBI differs from conventional radiation therapy in several unique ways. The limited maximum apertures available from teletherapy machines complicate it. Dose uniformity is compromised by tissue in homogeneities (i.e., variations in both body parts, thickness and tissue density). If the skin and the bone marrow are targeted for treatment, then the build-up region becomes a concern, especially for linac energies. Critical organ shielding must balance toxicity and control of circulating leukaemic cells. Thus, protocols often specify low dose rates to minimise toxicity.

Although the haematopoietic system is the target of TBI, normal tissues effectively limit the dose that can be safely delivered. The sparing of normal tissues with fractionated TBI was proposed by Peters and colleagues, showing less lung injury with fractionated TBI regimens.

Early reversible toxicity of radio-chemotherapy (partly with high risk of lethality) include nausea and vomiting, mucositis (oropharyngeal, gastro-intestinal), bone marrow aplasia, infections, haemorrhage, interstitial pneumonitis, alopecia, nail growth disorder and parotitis. Late toxicity of radio-chemotherapy include endocrine and reproductive gonadal insufficiency, growth disorders (in childhood), hypothyreosis, lung fibrosis, cataract, secondary malignancies, irreversible alopecia and cardiomyopathy.

BLK Experience

Since 2009, BLK has treated 180 patients with TBI for various conditions ranging from aplastic anaemia to peripheral T cell Lymphoma. Of these, 98 patients were treated with short course - single fraction TBI of 2 Gy and 82 patients were treated with long course – 12 Gy in three days TBI i.e. 2 Gy per fraction BD, 12 hours apart. For long course, lung shield and kidney blocks were used.