High-Dose Spatially Fractionated GRID Radiation Therapy (SFGRT): A Comparison of Treatment Outcomes With Cerrobend vs. MLC SFGRT

Neuner, Geoffrey; Mohiuddin, Majid; Walde, Noam Vander; Goloubeva, Olga; Ha, Jonathan; Yu, C; Regine, William F.

doi:10.1016/j.ijrobp.2011.01.065

Cited by 92 publications

(123 citation statements)

References 14 publications

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“…Spatially fractionated radiation therapy (also known as grid therapy) is a technique that has been introduced for treatment of patients with advanced bulky tumors (2) . In this technique, an open X‐ray field is being converted to a set of pencil beam type radiation fields using an external block (3) .…”

Section: Introductionmentioning

confidence: 99%

Is grid therapy useful for all tumors and every grid block design?

Gholami

Nedaie

Longo

et al. 2016

J Applied Clin Med Phys

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Grid therapy is a treatment technique that has been introduced for patients with advanced bulky tumors. The purpose of this study is to investigate the effect of the radiation sensitivity of the tumors and the design of the grid blocks on the clinical response of grid therapy. The Monte Carlo simulation technique is used to determine the dose distribution through a grid block that was used for a Varian 2100C linear accelerator. From the simulated dose profiles, the therapeutic ratio (TR) and the equivalent uniform dose (EUD) for different types of tumors with respect to their radiation sensitivities were calculated. These calculations were performed using the linear quadratic (LQ) and the Hug‐Kellerer (H‐K) models. The results of these calculations have been validated by comparison with the clinical responses of 232 patients from different publications, who were treated with grid therapy. These published results for different tumor types were used to examine the correlation between tumor radiosensitivity and the clinical response of grid therapy. Moreover, the influence of grid design on their clinical responses was investigated by using Monte Carlo simulations of grid blocks with different hole diameters and different center‐to‐center spacing. The results of the theoretical models and clinical data indicated higher clinical responses for the grid therapy on the patients with more radioresistant tumors. The differences between TR values for radioresistant cells and radiosensitive cells at 20 Gy and 10 Gy doses were up to 50% and 30%, respectively. Interestingly, the differences between the TR values with LQ model and H‐K model were less than 4%. Moreover, the results from the Monte Carlo studies showed that grid blocks with a hole diameters of 1.0 cm and 1.25 cm may lead to about 19% higher TR relative to the grids with hole diameters smaller than 1.0 cm or larger than 1.25 cm (with 95% confidence interval). In summary, the results of this study indicate that grid therapy is more effective for tumors with radioresistant characteristics than radiosensitive tumors.PACS number(s): 87.55.‐x

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Section: Introductionmentioning

confidence: 99%

Is grid therapy useful for all tumors and every grid block design?

Gholami

Nedaie

Longo

et al. 2016

J Applied Clin Med Phys

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“…One can argue that a similar or better cancer cell killing rate can be achieved by using uniform dose radiotherapy with a large dose; however, nonuniform field radiotherapy has demonstrated improved radiation tolerance and response when compared with uniform field radiotherapy for most tumors. [24][25][26][27] HDR VCBT also has a varied dose distribution across the tumor target, so it possibly possesses similar therapeutic advantage to that seen in the external beam nonuniform dose radiotherapy [most known as spatially fractionated (grid) radiotherapy]. Additionally, assuming the distribution of cancer cells follows the dose variation, it may provide an even bigger therapeutic advantage than that seen in randomly modulated external beam nonuniform (grid) field, which does not take into account cancer cell distribution nor the normal cell distribution in its planning.…”

Section: Discussionmentioning

confidence: 99%

Therapeutic analysis of high-dose-rate ¹⁹² Ir vaginal cuff brachytherapy for endometrial cancer using a cylindrical target volume model and varied cancer cell distributions

et al. 2015

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Purpose: To evaluate high-dose-rate (HDR) vaginal cuff brachytherapy (VCBT) in the treatment of endometrial cancer in a cylindrical target volume with either a varied or a constant cancer cell distributions using the linear quadratic (LQ) model. Methods: A Monte Carlo (MC) technique was used to calculate the 3D dose distribution of HDR VCBT over a variety of cylinder diameters and treatment lengths. A treatment planning system (TPS) was used to make plans for the various cylinder diameters, treatment lengths, and prescriptions using the clinical protocol. The dwell times obtained from the TPS were fed into MC. The LQ model was used to evaluate the therapeutic outcome of two brachytherapy regimens prescribed either at 0.5 cm depth (5.5 Gy × 4 fractions) or at the vaginal mucosal surface (8.8 Gy × 4 fractions) for the treatment of endometrial cancer. An experimentally determined endometrial cancer cell distribution, which showed a varied and resembled a half-Gaussian distribution, was used in radiobiology modeling. The equivalent uniform dose (EUD) to cancer cells was calculated for each treatment scenario. The therapeutic ratio (TR) was defined by comparing VCBT with a uniform dose radiotherapy plan in term of normal cell survival at the same level of cancer cell killing. Calculations of clinical impact were run twice assuming two different types of cancer cell density distributions in the cylindrical target volume: (1) a half-Gaussian or (2) a uniform distribution. Results: EUDs were weakly dependent on cylinder size, treatment length, and the prescription depth, but strongly dependent on the cancer cell distribution. TRs were strongly dependent on the cylinder size, treatment length, types of the cancer cell distributions, and the sensitivity of normal tissue. With a half-Gaussian distribution of cancer cells which populated at the vaginal mucosa the most, the EUDs were between 6.9 Gy × 4 and 7.8 Gy × 4, the TRs were in the range from (5.0) 4 to (13.4) 4 for the radiosensitive normal tissue depending on the cylinder size, treatment lengths, prescription depth, and dose as well. However, for a uniform cancer cell distribution, the EUDs were between 6.3 Gy × 4 and 7.1 Gy × 4, and the TRs were found to be between (1.4) 4 and (1.7) 4 . For the uniformly interspersed cancer and radio-resistant normal cells, the TRs were less than 1. The two VCBT prescription regimens were found to be equivalent in terms of EUDs and TRs. Conclusions: HDR VCBT strongly favors cylindrical target volume with the cancer cell distribution following its dosimetric trend. Assuming a half-Gaussian distribution of cancer cells, the HDR VCBT provides a considerable radiobiological advantage over the external beam radiotherapy (EBRT) in terms of sparing more normal tissues while maintaining the same level of cancer cell killing. But for the uniform cancer cell distribution and radio-resistant normal tissue, the radiobiology outcome of the HDR VCBT does not show an advantage over the EBRT. This study strongly suggests that radiation therapy desi...

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Section: Descriptionmentioning

confidence: 99%

“…Such fields have been known to allow a higher dose to the tumour at depth, while sparing normal tissue at shallower depths. Even though only a limited number of grid therapy cases are carried out in the clinic today, the responses have been encouraging with the achievement of a higher therapeutic ratio [5].Another technique, which by design incorporates high dose gradients within the treatment field, is microbeam radiation therapy (MRT), where the field is created as a composite of micro-scale beams using an x-ray synchrotron. The medical beam line of a synchrotron creates non-divergent photon beams with far higher dose rates than a linear accelerator, therefore delivering a high dose quickly, while maintaining dose modulation [6,7].…”

mentioning

confidence: 99%

Is There More to Radiotherapy than Hitting the Target?

Peng¹,

Suchowerska²,

Esteves³

et al. 2017

J Nurs Health Stud

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DescriptionOne in two cancer patients are routinely treated with radiotherapy, using a linear accelerator to deliver the radiation dose. Conventionally, a treatment meets guidelines when the tumour is uniformly irradiated, but the surrounding normal tissue is avoided [1]. However, our recent study upsets this radiation therapy "dogma" [2]. We have shown that a radiation field with many high dose gradients may have an advantage over a uniform field [2], because it is more lethal to cancer cells than to normal cells. We attribute this effect predominantly to the production, diffusion and response to radiation induced bystander signals, which is consistent with previous reports of up to 60% of cell death following irradiation being attributed to bystander effects [3,4].The use of a radiation field that delivers a non-uniform dose with high dose gradients is not new. Spatially fractionated radiotherapy or grid therapy, delivers radiation through a collimating grid block or by using the multileaf collimator of a linear accelerator. This approach creates an alternating peak and valley dose across the body surface with a spatial period of a few centimeters. At depth, the dose gradients will smear out and be reduced. Such fields have been known to allow a higher dose to the tumour at depth, while sparing normal tissue at shallower depths. Even though only a limited number of grid therapy cases are carried out in the clinic today, the responses have been encouraging with the achievement of a higher therapeutic ratio [5].Another technique, which by design incorporates high dose gradients within the treatment field, is microbeam radiation therapy (MRT), where the field is created as a composite of micro-scale beams using an x-ray synchrotron. The medical beam line of a synchrotron creates non-divergent photon beams with far higher dose rates than a linear accelerator, therefore delivering a high dose quickly, while maintaining dose modulation [6,7]. To date, only in-vitro [8] and in-vivo animal studies have been performed using MRT, achieving exceptional therapeutic outcomes with preferential tumour toxicity and high normal tissue tolerance [9]. The peak dose in the micro-sized beam is over a hundred times greater than conventional radiotherapy and the outcomes are difficult to explain using the conventional dogma of radiation therapy.The success of MRT has been attributed to the differential response between tumour and normal tissue, particularly in their vasculature [10], but this factor does not explain the invitro therapeutic advantages.Synchrotron facilities are currently not suitable for human cancer treatment, but it is feasible that the therapeutic advantages of MRT may in part be translated to the clinic using new generation linear accelerators. We questioned whether a radiation field created with linear accelerators, to give the finest possible collimated beams and therefore high dose gradients, could achieve a better therapeutic outcome than the conventional uniform field. By using the high definition micro-mult...

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High-Dose Spatially Fractionated GRID Radiation Therapy (SFGRT): A Comparison of Treatment Outcomes With Cerrobend vs. MLC SFGRT

Cited by 92 publications

References 14 publications

Is grid therapy useful for all tumors and every grid block design?

Is grid therapy useful for all tumors and every grid block design?

Therapeutic analysis of high-dose-rate ¹⁹² Ir vaginal cuff brachytherapy for endometrial cancer using a cylindrical target volume model and varied cancer cell distributions

Is There More to Radiotherapy than Hitting the Target?

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High-Dose Spatially Fractionated GRID Radiation Therapy (SFGRT): A Comparison of Treatment Outcomes With Cerrobend vs. MLC SFGRT

Cited by 92 publications

References 14 publications

Is grid therapy useful for all tumors and every grid block design?

Is grid therapy useful for all tumors and every grid block design?

Therapeutic analysis of high-dose-rate 192 Ir vaginal cuff brachytherapy for endometrial cancer using a cylindrical target volume model and varied cancer cell distributions

Is There More to Radiotherapy than Hitting the Target?

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Therapeutic analysis of high-dose-rate ¹⁹² Ir vaginal cuff brachytherapy for endometrial cancer using a cylindrical target volume model and varied cancer cell distributions