First French experiences of total body irradiations using helical TomoTherapy ®

Automatic planning of the lower extremities for total marrow irradiation using volumetric modulated arc therapy

PURPOSE

Total marrow (and lymphoid) irradiation (TMI-TMLI) is limited by the couch travel range of modern linacs, which forces the treatment delivery to be split into two plans with opposite orientations: a head-first supine upper-body plan, and a feet-first supine lower extremities plan. A specific field junction is thus needed to obtain adequate target coverage in the overlap region of the two plans. In this study, an automatic procedure was developed for field junction creation and lower extremities plan optimization.

METHODS

Ten patients treated with TMI-TMLI at our institution were selected retrospectively. The planning of the lower extremities was performed automatically. Target volume parameters (CTV_J‑V_98% > 98%) at the junction region and several dose statistics (D_98%, D_mean, and D_2%) were compared between automatic and manual plans. The modulation complexity score (MCS) was used to assess plan complexity.

RESULTS

The automatic procedure required 60-90 min, depending on the case. All automatic plans achieved clinically acceptable dosimetric results (CTV_J‑V_98% > 98%), with significant differences found at the junction region, where D_mean and D_2% increased on average by 2.4% (p < 0.03) and 3.0% (p < 0.02), respectively. Similar plan complexity was observed (median MCS = 0.12). Since March 2022, the automatic procedure has been introduced in our clinic, reducing the TMI-TMLI simulation-to-delivery schedule by 2 days.

CONCLUSION

The developed procedure allowed treatment planning of TMI-TMLI to be streamlined, increasing efficiency and standardization, preventing human errors, while maintaining the dosimetric plan quality and complexity of manual plans. Automated strategies can simplify the future adoption and clinical implementation of TMI-TMLI treatments in new centers.

Optimised conformal total body irradiation: a heterogeneous practice, so where next?

The use of volumetric arc therapy and inverse planning has been in routine use in radiotherapy for two decades. However, use in total body irradiation (TBI) has been more recent and few guidelines exist as to how to plan or verify. This has led to heterogeneous approaches. The goal of this review is to provide an overview of current advanced planning and dosimetry verification protocols used in optimised conformal TBI as a basis for investigating the need for greater standardisation in TBI.

Total marrow irradiation (TMI): Addressing an unmet need in hematopoietic cell transplantation - a single institution experience review

Purpose

TMI utilizes IMRT to deliver organ sparing targeted radiotherapy in patients undergoing hematopoietic cell transplantation (HCT). TMI addresses an unmet need, specifically patients with refractory or relapsed (R/R) hematologic malignancies who have poor outcomes with standard HCT regimens and where attempts to improve outcomes by adding or dose escalating TBI are not possible due to increased toxicities. Over 500 patients have received TMI at this center. This review summarizes this experience including planning and delivery, clinical results, and future directions.

Methods

Patients were treated on prospective allogeneic HCT trials using helical tomographic or VMAT IMRT delivery. Target structures included the bone/marrow only (TMI), or the addition of lymph nodes, and spleen (total marrow and lymphoid irradiation, TMLI). Total dose ranged from 12 to 20 Gy at 1.5-2.0 Gy fractions twice daily.

Results

Trials demonstrate engraftment in all patients and a low incidence of radiation related toxicities and extramedullary relapses. In R/R acute leukemia TMLI 20 Gy, etoposide, and cyclophosphamide (Cy) results in a 1-year non-relapse mortality (NRM) rate of 6% and 2-year overall survival (OS) of 48%; TMLI 12 Gy added to fludarabine (flu) and melphalan (mel) in older patients (≥ 60 years old) results in a NRM rate of 33% comparable to flu/mel alone, and 5-year OS of 42%; and TMLI 20 Gy/flu/Cy and post-transplant Cy (PTCy) in haplo-identical HCT results in a 2-year NRM rate of 13% and 1-year OS of 83%. In AML in complete remission, TMLI 20 Gy and PTCy results in 2-year NRM, OS, and GVHD free/relapse-free survival (GRFS) rates of 0%, 86·7%, and 59.3%, respectively.

Conclusion

TMI/TMLI shows significant promise, low NRM rates, the ability to offer myeloablative radiation containing regimens to older patients, the ability to dose escalate, and response and survival rates that compare favorably to published results. Collaboration between radiation oncology and hematology is key to successful implementation. TMI/TMLI represents a paradigm shift from TBI towards novel strategies to integrate a safer and more effective target-specific radiation therapy into HCT conditioning beyond what is possible with TBI and will help expand and redefine the role of radiotherapy in HCT.

Total body irradiation using volumetric modulated arc therapy, experience of a cancer hospital in Pakistan

Introduction:

To report the planning parameters, efficacy and toxicity of total body irradiation using volumetric modulated arc therapy (VMAT).

Methods:

From July 2019 till May 2021, nine patients treated with VMAT-based total body irradiation as a part of the myeloablative regimen for homologous stem cell transplant were evaluated. The CT acquisition, planning parameters, doses to target volume and critical structures were evaluated retrospectively.

Results:

Median age was 24 with median height 172 cm. Average Mean Lung dose was 9·5 Gy, mean dose to kidney was kidney dose 8·4 Gy, planning target volume (PTV) 95% was 98 % and mean heterogeneity index of PTV was 1·2 all patients. Total fraction delivery time including setup was 3·1 h while beam on time was 23 min. Main toxicity observed was mucositis and fatigue, while no Grade 3 or more acute radiation toxicity was observed.

Conclusion:

At our institution, high dose TBI performed with multi-isocentric VMAT is now a standard procedure. Though it is cumbersome and time-consuming process but VMAT offers an advantage of increased dose homogeneity in the target volume with reduction in doses to critical organs especially lungs and kidneys in comparison to standard source to skin distance technique, longer follow-up time is necessary to evaluate our method and long-term toxicity.

Total Body Irradiation in Haematopoietic Stem Cell Transplantation for Paediatric Acute Lymphoblastic Leukaemia: Review of the Literature and Future Directions

Total body irradiation (TBI) has been a pivotal component of the conditioning regimen for allogeneic myeloablative haematopoietic stem cell transplantation (HSCT) in very-high-risk acute lymphoblastic leukaemia (ALL) for decades, especially in children and young adults. The myeloablative conditioning regimen has two aims: (1) to eradicate leukaemic cells, and (2) to prevent rejection of the graft through suppression of the recipient's immune system. Radiotherapy has the advantage of achieving an adequate dose effect in sanctuary sites and in areas with poor blood supply. However, radiotherapy is subject to radiobiological trade-offs between ALL cell destruction, immune and haematopoietic stem cell survival, and various adverse effects in normal tissue. To diminish toxicity, a shift from single-fraction to fractionated TBI has taken place. However, HSCT and TBI are still associated with multiple late sequelae, leaving room for improvement. This review discusses the past developments of TBI and considerations for dose, fractionation and dose-rate, as well as issues regarding TBI setup performance, limitations and possibilities for improvement. TBI is typically delivered using conventional irradiation techniques and centres have locally developed heterogeneous treatment methods and ways to achieve reduced doses in several organs. There are, however, limitations in options to shield organs at risk without compromising the anti-leukaemic and immunosuppressive effects of conventional TBI. Technological improvements in radiotherapy planning and delivery with highly conformal TBI or total marrow irradiation (TMI), and total marrow and lymphoid irradiation (TMLI) have opened the way to investigate the potential reduction of radiotherapy-related toxicities without jeopardising efficacy. The demonstration of the superiority of TBI compared with chemotherapy-only conditioning regimens for event-free and overall survival in the randomised For Omitting Radiation Under Majority age (FORUM) trial in children with high-risk ALL makes exploration of the optimal use of TBI delivery mandatory. Standardisation and comprehensive reporting of conventional TBI techniques as well as cooperation between radiotherapy centres may help to increase the ratio between treatment outcomes and toxicity, and future studies must determine potential added benefit of innovative conformal techniques to ultimately improve quality of life for paediatric ALL patients receiving TBI-conditioned HSCT.

Automatic treatment planning for VMAT-based total body irradiation using Eclipse scripting

The purpose of this work is to establish an automated approach for a multiple isocenter volumetric arc therapy (VMAT)‐based TBI treatment planning approach. Five anonymized full‐body CT imaging sets were used. A script was developed to automate and standardize the treatment planning process using the Varian Eclipse v15.6 Scripting API. The script generates two treatment plans: a head‐first VMAT‐based plan for upper body coverage using four isocenters and a total of eight full arcs; and a feet‐first AP/PA plan with three isocenters that covers the lower extremities of the patient. PTV was the entire body cropped 5 mm from the patient surface and extended 3 mm into the lungs and kidneys. Two plans were generated for each case: one to a total dose of 1200 cGy in 8 fractions and a second one to a total dose of 1320 cGy in 8 fractions. Plans were calculated using the AAA algorithm and 6 MV photon energy. One plan was created and delivered to an anthropomorphic phantom containing 12 OSLDs for in‐vivo dose verification. For the plans prescribed to 1200 cGy total dose the following dosimetric results were achieved: median PTV V100% = 94.5%; median PTV D98% = 89.9%; median lungs Dmean = 763 cGy; median left kidney Dmean = 1058 cGy; and median right kidney Dmean = 1051 cGy. For the plans prescribed to 1320 cGy total dose the following dosimetric results were achieved: median PTV V100% = 95.0%; median PTV D98% = 88.7%; median lungs Dmean = 798 cGy; median left kidney Dmean = 1059 cGy; and median right kidney Dmean = 1064 cGy. Maximum dose objective was met for all cases. The dose deviation between the treatment planning dose and the dose measured by the OSLDs was within ±4%. In summary, we have demonstrated that scripting can produce high‐quality plans based on predefined dose objectives and can decrease planning time by automatic target and optimization contours generation, plan creation, field and isocenter placement, and optimization objectives setup.

A dosimetric evaluation of a novel technique using abutted radiation fields for myeloablative total body irradiation

Background:

The present study reports myeloablative total body irradiation (TBI) on an isocentrically mounted linac by laying the patient on the floor and management of abutting radiation fields and partial shielding of lungs. Dosimetrical efficacy of this novel technique was evaluated.

Materials and methods:

In this retrospective study, dosimetrical parameters from TBI plans on whole-body CT scans of 46 patients were analysed. The prescribed dose to TBI was 12 Gy in six fractions delivered over a period of 3 days for myeloablative conditioning. TrueBeam STx platform Linac (Varian Medical Systems Inc., Palo Alto, CA, USA) was used to deliver opposing fields. Radiation fields were abutted to form a single large field using an arithmetic formula at source-to-skin-distance of 210 cm.

Results:

Discrepancies in dose calculated by treatment planning system were within 1·6% accuracy, and dose profile at the junction of abutting radiation fields was reproduced within 3·0% accuracy. The real treatment time for each patient was ~30 minutes/fraction. Monitor unit was weighted for multiple sub-fields to achieve dose homogeneity within 5·0% throughout the whole body, and the mean dose to lung was ≤10 Gy.

Conclusion:

Our abutting radiation field technique for myeloablative TBI is feasible in any existing linac bunker. ‘Island-blocking’ is feasible in this technique using multi-leaf collimator. This technique is cost-effective as it does not require any costly equipment than the readily available equipment in any radiotherapy facility. In general, TBI requires laborious planning procedures and spacious linac bunkers; this novel technique has the potential to change previously held notions.

Feasibility of hybrid TomoHelical- and TomoDirect-based volumetric gradient matching technique for total body irradiation

BACKGROUND

Tomotherapy-based total body irradiation (TBI) is performed using the head-first position (HFP) and feet-first position (FFP) due to treatment length exceeding the 135 cm limit. To reduce the dosimetric variation at the match lines, we propose and verify a volumetric gradient matching technique (VGMT) by combining TomoHelical (TH) and TomoDirect (TD) modes.

METHODS

Two planning CT image sets were acquired with HFP and FFP using 15 × 55 × 18 cm3 of solid water phantom. Planning target volume (PTV) was divided into upper, lower, and gradient volumes. The junction comprised 2-cm thick five and seven gradient volumes (5-GVs and 7-GVs) to create a dose distribution with a gentle slope. TH-IMRT and TD-IMRT plans were generated with 5-GVs and 7-GVs. The setup error in the calculated dose was assessed by shifting dose distribution of the FFP plan by 5, 10, 15, and 20 mm in the longitudinal direction and comparing it with the original. Doses for 95% (D95) and 5% of the PTV (D5) were calculated for all simulated setup error plans. Absolute dose measurements were performed using an ionization chamber in the junction.

RESULTS

The TH&TD plan produced a linear gradient in junction volume, comparable to that of the TH&TH plan. D5 of the PTV was 110% of the prescribed dose when the FFP plan was shifted 0.7 cm and 1.2 cm in the superior direction for 5-GVs and 7-GVs. D95 of the PTV decreased to < 90% of the prescribed dose when the FF plan was shifted 1.1 cm and 1.3 cm in the inferior direction for 5-GVs and 7-GVs. The absolute measured dose showed a good correlation with the calculated dose in the gradient junction volume. The average percent difference (±SD) in all measured points was - 0.7 ± 1.6%, and the average dose variations between depths was - 0.18 ± 1.07%.

CONCLUSION

VGMT can create a linear dose gradient across the junction area in both TH&TH and TH&TD and can minimize the dose sensitivity to longitudinal setup errors in tomotherapy-based TBI.

Dose evaluation indices for total body irradiation using TomoDirect with different numbers of ports: A comparison with the TomoHelical method

TomoDirect has been reported to have some advantages over TomoHelical in delivering total body irradiation (TBI). This study aimed to investigate the relationships between the number of ports and the dose evaluation indices in low‐dose TBI in TomoDirect mode using 2–12 ports and to compare these data with those for the TomoHelical mode in a simulation study. Thirteen patients underwent low‐dose TBI in TomoHelical mode from June 2015 to June 2016. We used the same computed tomography data sets for these patients to create new treatment plans for upper‐body parts using TomoDirect mode with 2–12 beam angles as well as TomoHelical mode. The prescription was 4 Gy in two equal fractions. For the TomoDirect data, we generated plans with 2–12 ports with approximately equally spaced angles; the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.500, respectively. For the TomoHelical plans, the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.397, respectively. D2, D98, D50, and the homogeneity index (HI) were evaluated to compare TomoDirect plans having 2–12 ports with the TomoHelical plan. Using TomoDirect plans, D2 with four ports or fewer, D98 with 10 ports or fewer, D50 with four ports or fewer and HI with five ports or fewer showed statistically significantly worse results than the TomoHelical plan. With the TomoDirect plans, D2 with seven ports or more, D50 with eight ports or more, and HI with eight ports or more showed statistically significant improvement compared with the TomoHelical plan. All of the dose evaluation indices of the TomoDirect plans showed a tendency to improve as the number of ports increased. TomoDirect plans showed statistically significant improvement of D2, D50, and HI compared with the TomoHelical plan. Therefore, we conclude that TomoDirect can provide better dose distribution in low‐dose TBI with TomoTherapy.