Total body irradiation-based regimen in the conditioning of patients submitted to haploidentical stem cell transplantation

Knowledge-based planning for multi-isocenter VMAT total marrow irradiation

Purpose

Total marrow irradiation (TMI) involves optimization of extremely large target volumes and requires extensive clinical experience and time for both treatment planning and delivery. Although volumetric modulated arc therapy (VMAT) achieves substantial reduction in treatment delivery time, planning process still presents a challenge due to use of multiple isocenters and multiple overlapping arcs. We developed and evaluated a knowledge-based planning (KBP) model for VMAT-TMI to address these clinical challenges.

Methods

Fifty-one patients previously treated in our clinic were selected for the model training, while 22 patients from another clinic were used as a test set. All plans used a 3-isocenter to cover sub-target volumes of head and neck (HN), chest, and pelvis. Chest plan was performed first and then used as the base dose for both the HN and pelvis plans to reduce hot spots around the field junctions. This resulted in a wide range of dose-volume histograms (DVH). To address this, plans without the base-dose plan were optimized and added to the library to train the model.

Results

KBP achieved our clinical goals (95% of PTV receives 100% of Rx) in a single day, which used to take 4-6 days of effort without KBP. Statistically significant reductions with KBP were observed in the mean dose values to brain, lungs, oral cavity and lenses. KBP substantially improved 105% dose spillage (14.1% ± 2.4% vs 31.8% ± 3.8%), conformity index (1.51 ± 0.06 vs 1.81 ± 0.12) and homogeneity index (1.25 ± 0.02 vs 1.33 ± 0.03).

Conclusions

KBP improved dosimetric performance with uniform quality. It reduced dependence on planner experience and achieved a factor of 5 reduction in planning time to produce quality plans to allow its wide-spread clinical implementation.

Target Coverage and Normal Organ Sparing in Dose-Escalated Total Marrow and Lymphatic Irradiation: A Single-Institution Experience

Purpose/Objectives

The aim of this study is to report historical treatment planning experience at our institution for patients receiving total marrow and lymphatic irradiation (TMLI) as part of the conditioning regimen prior to hematopoietic stem cell transplant.

Materials/Methods

Based on a review of all historical clinical TMLI treatments plans, we retrieved a 12-Gy cohort of 108 patients with a prescription dose of 12 Gy to the skeletal bones, lymph nodes, spleen, and spinal canal, and retrieved a 20-Gy cohort of 120 patients with an escalated prescription dose of 20 Gy to the skeletal bones, lymph nodes, spleen, and spinal cord, and 12 Gy to the brain and liver. Representative dosimetric parameters including mean and median dose, D80, and D10 (dose covering 80% and 10% of the structure volume, respectively) for targets and normal organs were extracted and compared between the two groups of patients.

Results

For the 12-Gy cohort, the average mean dose for normal organs ranged from 18.3% to 78.3% of 12 Gy, and the average median dose ranged from 18.3% to 77.5% of 12 Gy. For the 20-Gy cohort, the average mean dose for normal organs ranged from 13.0% to 76.0% of 20 Gy, and the average median dose ranged from 12.5% to 75.0% of 20 Gy. Compared to the mean dose to normal organs in the 12-Gy cohort, the average mean dose to normal organs increased from 0.0% to 73.1%, with only four normal organs showing a >50% increase. Normal organ dose in TMLI plans using volumetric modulated arc therapy fields fell within the dose range in historical TMLI plans.

Conclusion

Dosimetric data in historical TMLI plans at our institution are summarized at prescription dose levels of 12 Gy and 20 Gy, respectively. Compared to the normal organ dose with a prescription dose of 12 Gy, the mean and median dose to most normal organs at an escalated prescription dose of 20 Gy had an increase less than prescription dose scaling. Dosimetric results from this study can be used as reference data to facilitate clinical implementation of TMLI at other institutions.

Feasibility of a novel dose fractionation strategy in TMI/TMLI

Background

To report our experience in planning and delivering total marrow irradiation (TMI) and total marrow and lymphatic irradiation (TMLI) in patients with hematologic malignancies.

Methods

Twenty-seven patients undergoing bone marrow transplantation were treated with TMI/TMLI using Helical Tomotherapy (HT). All skeletal bones exclusion of the mandible comprised the treatment target volume and, for TMLI, lymph node chains, liver, spleen and/or brain were also included according to the clinical indication. Planned dose of 8Gy in 2 fractions was delivered over 1 day for TMI while 10Gy in 2 fractions BID was used for TMLI. Organs at risk (OAR) contoured included the brain, brainstem, lens, eyes, optic nerves, parotids, oral cavity, lungs, heart, liver, kidneys, stomach, small bowel, bladder and rectum. In particular, a simple method to avoid hot or cold doses in the overlapping region was implemented and the plan sum was adopted to evaluate dose inhomogeneity. Furthermore, setup errors from 54 treatments were summarized to gauge the effectiveness of immobilization.

Results

During the TMI/TMLI treatment, no acute adverse effects occurred during the radiation treatment. Two patients suffered nausea or vomiting right after radiation course. For the 9 patients treated with TMI, the median dose reduction of major organs varied 30–65% of the prescribed dose, substantially lower than the traditional total body irradiation (TBI). Meanwhile, average biological equivalent doses to OARs with 8Gy/2F TMI approach were not different from the conventional 12Gy/6F TMI approach. In the dose junction region, the 93% of PTV was covered by the prescribed dose without obvious hotspots. For the 27 patients, the overall setup corrections were lower than 3 mm except those in the SI direction for abdomen-pelvis region, demonstrating excellent immobilization.

Conclusion

The present study confirmed the technical feasibility of HT-based TMI/TMLI delivering 8-10Gy in 2 fractions over 1 day. For patients undergoing hematopoietic cell transplantation the proposed 8Gy/2F TMI (or 10Gy/2F TMLI) strategy may be a novel approach to improve delivery efficiency, increase effective radiation dose to target while maintaining low risk of severe organ toxicities.

The Total Body Irradiation Schedule Affects Acute Leukemia Relapse After Matched T Cell-Depleted Hematopoietic Stem Cell Transplantation

PURPOSE

We sought to determine whether the total body irradiation (TBI) schedule affected outcome in patients with acute leukemia in complete remission who received T cell-depleted allogeneic hematopoietic stem cell transplantation from HLA identical siblings.

METHODS AND MATERIALS

The study recruited 55 patients (median age, 48 years; age range, 20-66 years; 30 men and 25 women; 34 with acute myeloid leukemia and 21 with acute lymphoid leukemia). Hyperfractionated TBI (HTBI) (1.2 Gy thrice daily for 4 days [for a total dose of 14.4 Gy] from day -12 to day -9) was administered to 29 patients. Single-dose TBI (STBI) (8 Gy, at a median dose rate of 10.7 cGy/min on day -9) was given to 26 patients.

RESULTS

All patients achieved primary, sustained engraftment with full donor-type chimerism. At 10 years, the overall cumulative incidence of transplant-related mortality was 11% (SE, ±0.1%). It was 7% (SE, ±0.2%) after HTBI and 15% (SE, ±0.5%) after STBI (P=.3). The overall cumulative incidence of relapse was 33% (SE, ±0.5). It was 13% (SE, ±0.5%) after HTBI and 46% (SE, ±1%) after STBI (P=.02). The overall probability of disease-free survival (DFS) was 59% (SE, ±7%). It was 67% (SE, ±0.84%) after HTBI and 37% (SE, ±1.4%) after STBI (P=.01). Multivariate analyses showed the TBI schedule was the only risk factor that significantly affected relapse and DFS (P=.01 and P=.03, respectively).

CONCLUSIONS

In patients with acute leukemia, HTBI is more efficacious than STBI in eradicating minimal residual disease after HLA-matched T cell-depleted hematopoietic stem cell transplantation, thus affecting DFS.

In haematopoietic SCT for acute leukemia TBI impacts on relapse but not survival: results of a multicentre observational study

The aim of this study was to determine whether parameters related to TBI impacted upon OS and relapse in patients with acute leukemia in CR who underwent haematopoietic SCT (HSCT) in 11 Italian Radiation Oncology Centres. Data were analysed from 507 patients (313 males; 194 females; median age 15 years; 318 with ALL; 188 with AML; 1 case not recorded). Besides 128 autologous transplants, donors included 192 matched siblings, 74 mismatched family members and 113 unrelated individuals. Autologous and allogeneic transplants were analysed separately. Median follow-up was 40.1 months. TBI schedules and HSCT type were closely related. Uni- and multi-variate analyses showed no parameter was significant for OS or relapse in autologous transplantation. Multivariate analysis showed type of transplant and disease impacted significantly on OS in allogeneic transplantation. Disease, GVHD and TBI dose were risk factors for relapse. This analysis illustrates that Italian Transplant Centre use of TBI is in line with international practice. Most Centres adopted a hyperfractionated schedule that is used worldwide (12 Gy in six fractions over 3 days), which appears to have become standard. TBI doses impacted significantly upon relapse rates.

Haploidentical transplantation for acute lymphoblastic leukemia in childhood

Haploidentical transplantation in childhood acute lymphoblastic leukemia (ALL) is a promising option for children lacking a suitable donor. We have updated our series of patients with ALL and report the results. Additionally, we reviewed the literature and try to embed our own experiences in the published results. We performed HLA-mismatched stem cell transplantations with megadoses of purified positively selected mobilized peripheral blood CD34+ progenitor cells (PBPC) from adult donors in 27 children with acute lymphoblastic leukemia (ALL) in first (CR1 n = 7), second (CR2 n = 10), or third (CR3 n = 4) complete remission, and in refractory state (NR n = 6). The patients received a mean number of 19.1+/-11.3 x 10(6)/kg purified CD34+ and a mean number of 15.5+/-24.2 x 10(3)/kg CD3+ T-cells. No additional graft-versus-host disease (GVHD) prophylaxis was used, except as short-term CSA in the first 3 patients. The myeloablative treatment was based on busulfan in 12 and on TBI in 14 patients. One patient was grafted with a non-myeloablative approach. Engraftment was rapid in 26 patients, with two patients suffering from a rejection. These two and one patient with initial non-engraftment had been successfully regrafted. The probability of survival of the total group is 0.34+/-0.09; the 12 patients transplanted in remission showed a probability of survival of 0.44+/-0.11. None of the patients transplanted in non-remission survived. There was no statistical difference in survival for patients with a 1, 2 or 3 antigen mismatched donor (out of 6 HLA antigens) or for patients in 1st, 2nd or 3rd remission. Causes of death were relapses in 10 patients, veno-occlusive disease (VOD) in 1, multi-organ failure (MOF) in 2 and infections in 4 patients. 3/24 evaluable patients without any additional GVHD-prophylaxis developed grade 1 or 2 GVHD. Ten patients were treated with additional donor lymphocyte infusion (DLI), from which 4 developed a maximum grade 3 GVHD. We conclude that the HLA barrier can be overcome by transplantation of megadoses of highly purified CD34+ PBPC and GVHD can effectively be prevented. This approach offers a promising treatment option for patients with acute lymphoblastic leukemia needing urgently transplantation but lacking a suitable donor.

Cataracts in patients receiving stem cell transplantation after conditioning with total body irradiation

One hundred and ninety-three patients with hematological malignancies and a follow-up > or =1 year, treated with stem cell transplantation (45 autologous, 99 allogeneic T cell-depleted matched, 49 allogeneic T cell-depleted mismatched) from July 1985 to May 1998, were considered evaluable for the development of cataracts. Total body irradiation (TBI), administered either according to a hyperfractionated scheme (HTBI) or in a single dose (STBI), was employed in the conditioning regimens. HTBI was prescribed in 94% of patients undergoing allogeneic matched transplant, while STBI was used in 71% of patients receiving allogeneic mismatched and in all patients undergoing autologous transplant. The median follow-up was 7.56 years in the HTBI and 3.02 years in the STBI group. Among the different risk factors analyzed by univariate analysis only the TBI scheme and type of transplant reached statistical significance (P < 0.0001 and P < 0.001, respectively). By multivariate analysis only the TBI scheme was an independent factor for cataract development (STBI vs HTBI RR 7.2; P < 0.01). Our results showed that STBI is more cataractogenic than HTBI. The incidence of cataract we observed was among the lowest described in the literature. T cell depletion, because it prevents graft-versus-host disease and reduces the protracted use of post-transplant steroids, explains the results we obtained.