Purpose/Objective(s)Total lymphatic irradiation (TLI) is a procedure in which a patient's major lymph nodes and spleen are treated with low doses of radiation for recipient immunosuppression as part of multi-agent conditioning for cardiac, lung or hematopoietic stem cell transplantation, to facilitate engraftment and to decrease the risk of rejection. TLI is considered an attractive option instead of total body irradiation (TBI) to mitigate side effects of radiation exposure to normal tissues. There are no established guidelines on technique and dose fractionation. Herein, we share our experience.Materials/MethodsRetrospective review of children who received TLI for hematopoietic stem cell transplants at the hospital was done.ResultsTwenty-two patients who had TLI from 2004 to 2020, with a median age of 7.5 years (range 0.9-19.0) were included. Twelve had benign conditions and 10 had malignant conditions. Eighteen had haploidentical grafts, 2 had matched sibling and 2 had unrelated donors. Four patients had previously failed engraftment prior to TLI. Conditioning included multi-agent chemotherapy for all including rabbit-ATG for 12 patients. All patients had computer-tomographic scans simulation except for 2 patients who were treated in the earlier years when only orthogonal XR was available. Dose fractionation was single prior to 2017 (5-7Gy/1#) and in recent times more fractionated (6-7.5Gy/3#). The treatment targets were the spleen and the following nodal stations: cervical, axillary, mediastinal, hilar, paraaortic, pelvic, inguinal and femoral. Normal organs including the medial thyroid, heart, lungs, and abdominal organs were shielded with multi-leaf collimators using three-dimensional conformal technique (Figure 1, 2). Of 12 patients with benign conditions, all are alive at last follow up. Of 10 patients with malignant conditions, 3 are dead from disease. Five out of 12 patients who had haploidentical grafts, 0/2 matched sibling graft and 1/2 unrelated grafts experienced rejection. The median follow up is 14.0 months (IQR 6-41.5). None developed acute pneumonitis. One patient developed thyroid cancer 14 years after TLI.ConclusionHerein we describe our TLI experience and technique. More studies should be undertaken to evaluate the safety and efficacy of TLI compared to TBI. Going forward, a consensus on technique and dose should be developed. Total lymphatic irradiation (TLI) is a procedure in which a patient's major lymph nodes and spleen are treated with low doses of radiation for recipient immunosuppression as part of multi-agent conditioning for cardiac, lung or hematopoietic stem cell transplantation, to facilitate engraftment and to decrease the risk of rejection. TLI is considered an attractive option instead of total body irradiation (TBI) to mitigate side effects of radiation exposure to normal tissues. There are no established guidelines on technique and dose fractionation. Herein, we share our experience. Retrospective review of children who received TLI for hematopoietic stem cell transplants at the hospital was done. Twenty-two patients who had TLI from 2004 to 2020, with a median age of 7.5 years (range 0.9-19.0) were included. Twelve had benign conditions and 10 had malignant conditions. Eighteen had haploidentical grafts, 2 had matched sibling and 2 had unrelated donors. Four patients had previously failed engraftment prior to TLI. Conditioning included multi-agent chemotherapy for all including rabbit-ATG for 12 patients. All patients had computer-tomographic scans simulation except for 2 patients who were treated in the earlier years when only orthogonal XR was available. Dose fractionation was single prior to 2017 (5-7Gy/1#) and in recent times more fractionated (6-7.5Gy/3#). The treatment targets were the spleen and the following nodal stations: cervical, axillary, mediastinal, hilar, paraaortic, pelvic, inguinal and femoral. Normal organs including the medial thyroid, heart, lungs, and abdominal organs were shielded with multi-leaf collimators using three-dimensional conformal technique (Figure 1, 2). Of 12 patients with benign conditions, all are alive at last follow up. Of 10 patients with malignant conditions, 3 are dead from disease. Five out of 12 patients who had haploidentical grafts, 0/2 matched sibling graft and 1/2 unrelated grafts experienced rejection. The median follow up is 14.0 months (IQR 6-41.5). None developed acute pneumonitis. One patient developed thyroid cancer 14 years after TLI. Herein we describe our TLI experience and technique. More studies should be undertaken to evaluate the safety and efficacy of TLI compared to TBI. Going forward, a consensus on technique and dose should be developed.