Comparison of Treatment Planning Approaches for Spatially Fractionated Irradiation of Deep Tumors

Sheikh, Khadija; McNutt, Todd; Bell, Leslie A.; Moore, Joseph A.; Hrinivich, William T.; Teslow, T.; Laub, Wolfram; Yan, Yulong; Wong, John W.; Meyer, Jeffrey

doi:10.1016/j.ijrobp.2018.07.1418

Cited by 2 publications

(5 citation statements)

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“…A major difference of our study from the previous two‐dimensional‐GRID therapy approach, tomotherapy or MLC‐based studies was that our treatment planning approach uses an MLC‐based, 3D‐conformal forward planning technique with no beam modulation. Therefore, this MLC cross‐firing procedure preserves the characteristics of 3D‐conformal radiation therapy and provides all dosimetry information without the need for patient‐specific QA.…”

Section: Discussionmentioning

confidence: 99%

“…Currently, MV GRID therapy treatments are delivered using a high attenuation GRID‐block with divergent holes, with step and shoot multileaf collimator (MLC) control points, and/or Tomotherapy machines . Although, the treatment planning studies for GRID therapy using tomotherapy and step and shoot MLCs are evolving, these techniques require longer treatment times due to beam modulation and need patient‐specific quality assurance (QA).…”

Section: Introductionmentioning

confidence: 99%

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A novel, yet simple MLC‐based 3D‐crossfire technique for spatially fractionated GRID therapy treatment of deep‐seated bulky tumors

Pokhrel

Halfman

Sanford

et al. 2020

J Applied Clin Med Phys

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Purpose Treating deep‐seated bulky tumors with traditional single‐field Cerrobend GRID‐blocks has many limitations such as suboptimal target coverage and excessive skin toxicity. Heavy traditional GRID‐blocks are a concern for patient safety at various gantry‐angles and dosimetric detail is not always available without a GRID template in user’s treatment planning system. Herein, we propose a simple, yet clinically useful multileaf collimator (MLC)‐based three‐dimensional (3D)‐crossfire technique to provide sufficient target coverage, reduce skin dose, and potentially escalate tumor dose to deep‐seated bulky tumors. Materials/methods Thirteen patients (multiple sites) who underwent conventional single‐field cerrobend GRID‐block therapy (maximum, 15 Gy in 1 fraction) were re‐planned using an MLC‐based 3D‐crossfire method. Gross tumor volume (GTV) was used to generate a lattice pattern of 10 mm diameter and 20 mm center‐to‐center mimicking conventional GRID‐block using an in‐house MATLAB program. For the same prescription, MLC‐based 3D‐crossfire grid plans were generated using 6‐gantry positions (clockwise) at 60° spacing (210°, 270°, 330°, 30°, 90°, 150°, therefore, each gantry angle associated with a complement angle at 180° apart) with differentially‐weighted 6 or 18 MV beams in Eclipse. For each gantry, standard Millenium120 (Varian) 5 mm MLC leaves were fit to the grid‐pattern with 90° collimator rotation, so that the tunneling dose distribution was achieved. Acuros‐based dose was calculated for heterogeneity corrections. Dosimetric parameters evaluated include: mean GTV dose, GTV dose heterogeneities (peak‐to‐valley dose ratio, PVDR), skin dose and dose to other adjacent critical structures. Additionally, planning time and delivery efficiency was recorded. With 3D‐MLC, dose escalation up to 23 Gy was simulated for all patient's plans. Results All 3D‐MLC crossfire GRID plans exhibited excellent target coverage with mean GTV dose of 13.4 ± 0.5 Gy (range: 12.43–14.24 Gy) and mean PVDR of 2.0 ± 0.3 (range: 1.7–2.4). Maximal and dose to 5 cc of skin were 9.7 ± 2.7 Gy (range: 5.4–14.0 Gy) and 6.3 ± 1.8 Gy (range: 4.1–11.1 Gy), on average respectively. Three‐dimensional‐MLC treatment planning time was about an hour or less. Compared to traditional GRID‐block, average beam on time was 20% less, while providing similar overall treatment time. With 3D‐MLC plans, tumor dose can be escalated up to 23 Gy while respecting skin dose tolerances. Conclusion The simple MLC‐based 3D‐crossfire GRID‐therapy technique resulted in enhanced target coverage for de‐bulking deep‐seated bulky tumors, reduced skin toxicity and spare adjacent critical structures. This simple MLC‐based approach can be easily adopted by any radiotherapy center. It provides detailed dosimetry and a safe and effective treatment by eliminating the heavy physical GRID‐block and could potentially provide same day treatment. Prospective clinical trial with higher tumor‐dose to bulky deep‐seated tumors is anticipated.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A novel, yet simple MLC‐based 3D‐crossfire technique for spatially fractionated GRID therapy treatment of deep‐seated bulky tumors

Pokhrel

Halfman

Sanford

et al. 2020

J Applied Clin Med Phys

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“…Target edges were arranged 8 mm from GTV edge in the left-right and anterior-posterior directions. Similar to previous work that investigated various photon GRID methods, plans were created for targets spaced at 2 cm [ 14 ] and 3 cm [ 7 , 8 ]. Supplemental Table S1 shows dose objectives for the targets; objectives were included to minimize the OAR dose, which depended on the anatomic site and geometry.…”

Section: Methodsmentioning

confidence: 99%

“…A single 15- to 20-Gy fraction is followed by a traditional course of treatment [ 4 ]. More recent GRID delivery methods have used multileaf collimator modulation, volumetric modulated arc therapy (VMAT), or tomotherapy [ 5 – 7 ]. However, delivery of high-dose GRID therapy may not be possible with the above techniques, particularly in situations where critical organs lie adjacent to tumor and/or the tumors are particularly remote from the skin surface.…”

Section: Introductionmentioning

confidence: 99%

“…A solution, which maintains the unique geometry of high-dose “islands” within the tumor, is to dose paint 3-dimensional target structures along the axis of the tumor. This approach has been studied using VMAT and tomotherapy [ 7 ]. The objectives of this study were to compare the dosimetry of VMAT with a PBS-based GRID approach using cylindrical target structures in 5 sample patients, and to evaluate the robustness of PBS-based GRID in 2 clinical patients treated on an ongoing clinical trial (NCT05121545) [ 12 ].…”

Section: Introductionmentioning

confidence: 99%

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Treatment Planning of Bulky Tumors Using Pencil Beam Scanning Proton GRID Therapy

Halthore

Fellows²,

Tran³

et al. 2023

International Journal of Particle Therapy

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Purpose To compare spatially fractionated radiation therapy (GRID) treatment planning techniques using proton pencil-beam-scanning (PBS) and photon therapy. Materials and Methods PBS and volumetric modulated arc therapy (VMAT) GRID plans were retrospectively generated for 5 patients with bulky tumors. GRID targets were arranged along the long axis of the gross tumor, spaced 2 and 3 cm apart, and treated with a prescription of 18 Gy. PBS plans used 2- to 3-beam multiple-field optimization with robustness evaluation. Dosimetric parameters including peak-to-edge ratio (PEDR), ratio of dose to 90% of the valley to dose to 10% of the peak VPDR(D90/D10), and volume of normal tissue receiving at least 5 Gy (V5) and 10 Gy (V10) were calculated. The peak-to-valley dose ratio (PVDR), VPDR(D90/D10), and organ-at-risk doses were prospectively assessed in 2 patients undergoing PBS-GRID with pretreatment quality assurance computed tomography (QACT) scans. Results PBS and VMAT GRID plans were generated for 5 patients with bulky tumors. Gross tumor volume values ranged from 826 to 1468 cm3. Peak-to-edge ratio for PBS was higher than for VMAT for both spacing scenarios (2-cm spacing, P = .02; 3-cm spacing, P = .01). VPDR(D90/D10) for PBS was higher than for VMAT (2-cm spacing, P = .004; 3-cm spacing, P = .002). Normal tissue V5 was lower for PBS than for VMAT (2-cm spacing, P = .03; 3-cm spacing, P = .02). Normal tissue mean dose was lower with PBS than with VMAT (2-cm spacing, P = .03; 3-cm spacing, P = .02). Two patients treated using PBS GRID and assessed with pretreatment QACT scans demonstrated robust PVDR, VPDR(D90/D10), and organs-at-risk doses. Conclusions The PEDR was significantly higher for PBS than VMAT plans, indicating lower target edge dose. Normal tissue mean dose was significantly lower with PBS than VMAT. PBS GRID may result in lower normal tissue dose compared with VMAT plans, allowing for further dose escalation in patients with bulky disease.

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Comparison of Treatment Planning Approaches for Spatially Fractionated Irradiation of Deep Tumors

Cited by 2 publications

References 0 publications

A novel, yet simple MLC‐based 3D‐crossfire technique for spatially fractionated GRID therapy treatment of deep‐seated bulky tumors

A novel, yet simple MLC‐based 3D‐crossfire technique for spatially fractionated GRID therapy treatment of deep‐seated bulky tumors

Treatment Planning of Bulky Tumors Using Pencil Beam Scanning Proton GRID Therapy

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