Dr. Shikha Halder
Director & Senior Consultant
Radiation Oncology
BLK Super Speciality
Hospital, New Delhi
Total Body Irradiation Post Stem Cell
Transplant
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.