Is the α/β Value for Prostate Tumours Low Enough to be Safely Used in Clinical Trials?

Daşu, Alexandru

doi:10.1016/j.clon.2007.02.007

Cited by 160 publications

(87 citation statements)

References 83 publications

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“…A lower

α / β

value of 1.5 Gy and clonogen density of 10 5 appeared to reproduce, on average, the observed control of 70%–80%, confirming the hypothesis that a lower

α / β

ratio could be more appropriate to model its TCP (26) . For prostate HDR brachytherapy, this result seems to be in accordance with the fact that large

α / β

ratios produce steeper dose response curves that are more sensitive to the large dose gradients characterizing these types of treatments.…”

Section: Discussionsupporting

confidence: 62%

“…Due to the variety of radiobiological parameters associated with prostate TCP modeling in the literature, 24 , 25 , 26 , 27 , 28 in this study various combinations were tested in order to match the average biochemical control recorded in ten years of HDR data collection at our institution. A lower

α / β

value of 1.5 Gy and clonogen density of 10 5 appeared to reproduce, on average, the observed control of 70%–80%, confirming the hypothesis that a lower

α / β

ratio could be more appropriate to model its TCP (26) .…”

Section: Discussionmentioning

confidence: 99%

“…TCP values were obtained by using a Poisson model, (21) while NTCP parameters were obtained by using a Lyman‐Kutcher‐Burman (LKB) model 22 , 23 . Since there is much discussion on the appropriate parameters to be used in order to model tumor control for prostate cases, 24 , 25 , 26 , 27 , 28 different combinations of modeling values were used in this analysis. As previously performed by Uzan and Nahum, (20) the

α / β

ratio was varied between 5 and 1.5 Gy.…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Comparison of IPSA and HIPO inverse planning optimization algorithms for prostate HDR brachytherapy

Panettieri

Smith

Mason

et al. 2014

J Applied Clin Med Phys

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Publications have reported the benefits of using high‐dose‐rate brachytherapy (HDRB) for the treatment of prostate cancer, since it provides similar biochemical control as other treatments while showing lowest long‐term complications to the organs at risk (OAR). With the inclusion of anatomy‐based inverse planning optimizers, HDRB has the advantage of potentially allowing dose escalation. Among the algorithms used, the Inverse Planning Simulated Annealing (IPSA) optimizer is widely employed since it provides adequate dose coverage, minimizing dose to the OAR, but it is known to generate large dwell times in particular positions of the catheter. As an alternative, the Hybrid Inverse treatment Planning Optimization (HIPO) algorithm was recently implemented in Oncentra Brachytherapy V. 4.3. The aim of this work was to compare, with the aid of radiobiological models, plans obtained with IPSA and HIPO to assess their use in our clinical practice. Thirty patients were calculated with IPSA and HIPO to achieve our department's clinical constraints. To evaluate their performance, dosimetric data were collected: Prostate PTV D90(%),V100(%),V150(%), and V200(%), Urethra D10(%), Rectum D2cc(%), and conformity indices. Additionally tumor control probability (TCP) and normal tissue complication probability (NTCP) were calculated with the BioSuite software. The HIPO optimization was performed firstly with Prostate PTV (HIPOPTV) and then with Urethra as priority 1 (HIPOurethra). Initial optimization constraints were then modified to see the effects on dosimetric parameters, TCPs, and NTCPs. HIPO optimizations could reduce TCPs up to 10%–20% for all PTVs lower than 74 cm3. For the urethra, IPSA and HIPOurethra provided similar NTCPs for the majority of volume sizes, whereas HIPOPTV resulted in large NTCP values. These findings were in agreement with dosimetric values. By increasing the PTV maximum dose constraints for HIPOurethra plans, TCPs were found to be in agreement with IPSA without affecting the urethral NTCPs.PACS numbers: 87.55.‐x, 87.55.de, 87.55.dh, 87.53.Jw

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“…A lower

α / β

value of 1.5 Gy and clonogen density of 10 5 appeared to reproduce, on average, the observed control of 70%–80%, confirming the hypothesis that a lower

α / β

ratio could be more appropriate to model its TCP (26) . For prostate HDR brachytherapy, this result seems to be in accordance with the fact that large

α / β

ratios produce steeper dose response curves that are more sensitive to the large dose gradients characterizing these types of treatments.…”

Section: Discussionsupporting

confidence: 62%

α / β

value of 1.5 Gy and clonogen density of 10 5 appeared to reproduce, on average, the observed control of 70%–80%, confirming the hypothesis that a lower

α / β

ratio could be more appropriate to model its TCP (26) .…”

Section: Discussionmentioning

confidence: 99%

α / β

ratio was varied between 5 and 1.5 Gy.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Comparison of IPSA and HIPO inverse planning optimization algorithms for prostate HDR brachytherapy

Panettieri

Smith

Mason

et al. 2014

J Applied Clin Med Phys

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“…Based on the limited data available, this uncertainty seems to be larger for RBE min . It has been suggested that RBE min could take values larger as well as smaller than unity (Daşu 2007, Carabe-Fernandez et al 2007.…”

Section: Methodsmentioning

confidence: 99%

Clinical consequences of relative biological effectiveness variations in proton radiotherapy of the prostate, brain and liver

et al. 2013

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Proton relative biological effectiveness (RBE) is known to depend on the (α/β) x of irradiated tissues, with evidence of ∼60% variation over (α/β) x values from 1-10 Gy. The range of (α/β) x values reported for prostate tumors (1.2-5.0 Gy), brain tumors (10-15 Gy) and liver tumors (13-17 Gy) imply that the proton RBE for these tissues could vary significantly compared to the commonly used generic value of 1.1. Our aim is to evaluate the impact of this uncertainty on the proton dose in Gy(RBE) absorbed in normal and tumor tissues. This evaluation was performed for standard and hypofractionated regimens. RBE-weighted total dose (RWTD) distributions for 15 patients (five prostate tumors, five brain tumors and five liver tumors) were calculated using an in-house developed RBE model as a function of dose, dose-averaged linear energy transfer (LET d ) and (α/β) x . Variations of the dose-volume histograms (DVHs) for the gross tumor volume (GTV) and the organs at risk due to changes of (α/β) x and fractionation regimen were calculated and the RWTD received by 10% and 90% of the organ volume reported. The goodness of the plan, bearing the uncertainties, was then evaluated compared to the delivered plan, which considers a constant RBE of 1.1. For standard fractionated regimens, the prostate tumors, liver tumors and all critical structures in the brain showed typically larger RBE values than 1.1. However, in hypofractionated regimens lower values of RBE than 1.1 were observed in most cases. Based on DVH analysis we found that the RBE variations were clinically significant in particular for the prostate GTV and the critical structures in the brain. Despite the uncertainties in the biological input parameters when estimating RBE values, the results show that the use of a variable RBE with dose, LET d and (α/β) x could help to further optimize the target dose in proton treatment

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“…However, for less responsive tumor cells (SF 2 (36). However, the uncertainty of SF 2 could be notable (37).…”

Section: Contrast Between Hypofractionation and Standard Fractionationmentioning

confidence: 99%

Effect of Hypofractionation on Prostate Cancer Radiotherapy

Arabpour

Shahbazi‐Gahrouei

2017

Int J Cancer Manag

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Context: Prior research over the past few decades has shown that the hypofractionated external beam radiation therapy could be a valuable method with an outstanding potential to treat the prostate cancer. The alpha-beta ratio (α/β) is an indication of the fractionation sensitivity of a particular cell type. Values of α/β ≥ 10 Gy are responsible for early-responding normal tissues and most tumors, while values of α/β < 5 Gy are for late-responding normal tissues. The α/β ratio could be raised by either a local tumor control increase or a decrease of normal tissue late effects through the application of an unconventional fractionation schedules. Evidence Acquisition: This review article aimed to investigation the details of radiobiological and clinical trials which are reported to highlight the characteristics of hypofractionation for the prostate cancer treatment based on the investigation of clinical results from hypofractionated treatments. Results:With the sufficient radiobiological and physiological research studies, it may be claimed that if α/β value for prostate cancer is less than the adjacent surrounding organs at risk and by applying fewer and larger fractions; a better therapeutic ratio can be achieved for the patient. Conclusions: Radiobiological modeling can play a major role in the design of new protocols. Also, one should be aware that in modeling the hypofractionated treatment, normal tissue iso-effects are significantly important and some assumptions needed to be made regarding α/β values for the critical normal tissue complication endpoint.

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Is the α/β Value for Prostate Tumours Low Enough to be Safely Used in Clinical Trials?

Cited by 160 publications

References 83 publications

Comparison of IPSA and HIPO inverse planning optimization algorithms for prostate HDR brachytherapy

Comparison of IPSA and HIPO inverse planning optimization algorithms for prostate HDR brachytherapy

Clinical consequences of relative biological effectiveness variations in proton radiotherapy of the prostate, brain and liver

Effect of Hypofractionation on Prostate Cancer Radiotherapy

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