Initial experience of hypofractionated radiation retreatment with true beam and flattening filter free beam in selected case reports of recurrent nasopharyngeal carcinoma

Alongi, Filippo; Clerici, Elena; Pentimalli, S.; Mancosu, P.; Scorsetti, Marta

doi:10.1016/j.rpor.2012.07.012

Cited by 13 publications

(5 citation statements)

References 35 publications

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“…There are only a few reports that have mentioned the use of modern VMAT technique for recurrent nasopharyngeal cancer in the salvage SBRT setting [31]. Here, we report the dosimetric results of 10 recurrent NPC patients by creating salvage SBRT treatment plans and demonstrate the feasibility of such salvage re-irradiation approaches by comparing the noncoplanar VMAT (HA) with the coplanar VMAT (RA) technique.…”

Section: Discussionmentioning

confidence: 92%

Dosimetric comparison between RapidArc and HyperArc techniques in salvage stereotactic body radiation therapy for recurrent nasopharyngeal carcinoma

Lee

Lin

et al. 2020

Radiat Oncol

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Background: To evaluate dosimetric differences of salvage irradiations using two commercially available volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) techniques: RapidArc (RA) and HyperArc (HA), for recurrent nasopharyngeal carcinoma (NPC) after initial radiation therapy. Methods: Ten patients with recurrent NPC status previously treated with radiation therapy were considered suitable candidates for salvage SBRT using VMAT approach. Two separate treatment plans were created with HA and RA techniques for each case, with dosimetric outcomes compared with respect to tumor target coverage and organs-atrisk (OARs) sparing. Furthermore, the cumulative radiobiological effects to the relevant OARs from the original radiotherapy to the respective salvage SBRT plans were analyzed in terms of biologically effective dose (BED). Results: Treatment with HA exhibited similar target dose coverage as with RA, while delivering a higher mean dose to the targets. Using RA technique, the mean maximal doses to optic apparatus and the mean brain dose were reduced by 1 to 1.5 Gy, comparing to HA technique. The conformity index, gradient radius, and intermediate dose spillage in HA plans were significantly better than those in RA. With HA technique, the volume of brain receiving 12 Gy or more was reduced by 44%, comparing to RA technique. The cumulative BEDs to spinal cord and optic apparatus with RA technique were 1 to 2 Gy 3 less than those with HA. HA technique significantly reduced the volume within body that received more than 100 Gy. Conclusions: With better dose distribution than RA while maintaining sufficient target dose coverage, HA represents an attractive salvage SBRT technique for recurrent NPC.

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Section: Discussionmentioning

confidence: 92%

Dosimetric comparison between RapidArc and HyperArc techniques in salvage stereotactic body radiation therapy for recurrent nasopharyngeal carcinoma

Lee

Lin

et al. 2020

Radiat Oncol

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“…Hence, further studies with a range of fractionated does with OER correction and equivalent BED on in-vivo models as well as fine-tuning of the chemoRT regimen might be necessary to ascertain the exact dose for translating this to the clinics. Although previous studies have found hypofractionation schemes for re-RT in NPC patients to be generally safe, effective and timesaving (36)(37)(38), the number of patients treated with this technique is too small make any definite conclusions.…”

Section: Discussionmentioning

confidence: 93%

Patient-Derived Nasopharyngeal Cancer Organoids for Disease Modeling and Radiation Dose Optimization

Lucky

Law²,

Lui

et al. 2021

Front. Oncol.

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Effective radiation treatment (RT) for recurrent nasopharyngeal cancers (NPC), featuring an intrinsic hypoxic sub-volume, remains a clinical challenge. Lack of disease‐specific in-vitro models of NPC, together with difficulties in establishing patient derived xenograft (PDX) models, have further hindered development of personalized therapeutic options. Herein, we established two NPC organoid lines from recurrent NPC PDX models and further characterized and compared these models with original patient tumors using RNA sequencing analysis. Organoids were cultured in hypoxic conditions to examine the effects of hypoxia and radioresistance. These models were then utilized to determine the radiobiological parameters, such as α/β ratio and oxygen enhancement ratio (OER), characteristic to radiosensitive normoxic and radioresistant hypoxic NPC, using simple dose-survival data analytic tools. The results were further validated in-vitro and in-vivo, to determine the optimal boost dose and fractionation regimen required to achieve effective NPC tumor regression. Despite the differences in tumor microenvironment due to the lack of human stroma, RNA sequencing analysis revealed good correlation of NPC PDX and organoid models with patient tumors. Additionally, the established models also mimicked inter-tumoral heterogeneity. Hypoxic NPC organoids were highly radioresistant and had high α/β ratio compared to its normoxic counterparts. In-vitro and in-vivo fractionation studies showed that hypoxic NPC was less sensitive to RT fractionation scheme and required a large bolus dose or 1.4 times of the fractionated dose that was effective against normoxic cells in order to compensate for oxygen deficiency. This study is the first direct experimental evidence to predict optimal RT boost dose required to cause sufficient damage to recurrent hypoxic NPC tumor cells, which can be further used to develop dose-painting algorithms in clinical practice.

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“…with summation of series of MLC shaped fields. [32][33][34][35][36][37] There are multiple factors that influence the Sc values: in particular, photons are scattered by structures in the accelerator head (primary collimator, flattening filter, the secondary collimator), tertiary collimators (MLCs and wedges), photons and electrons backscatter into the monitor chamber, and at very small field sizes, a portion of the X-ray source is obscured by the collimators. In recent times, linear accelerator manufacturers have made provisions to deliver radiation therapy treatments with the flattening filter removed from a traditional medical accelerator.…”

Section: Discussionmentioning

confidence: 99%

Measurement and comparison of head scatter factor for 7 MV unflattened (FFF) and 6 MV flattened photon beam using indigenously designed columnar mini phantom

Sigamani

Nambiraj

Sinha

et al. 2015

Reports of Practical Oncology & Radiotherapy

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Initial experience of hypofractionated radiation retreatment with true beam and flattening filter free beam in selected case reports of recurrent nasopharyngeal carcinoma

Cited by 13 publications

References 35 publications

Dosimetric comparison between RapidArc and HyperArc techniques in salvage stereotactic body radiation therapy for recurrent nasopharyngeal carcinoma

Dosimetric comparison between RapidArc and HyperArc techniques in salvage stereotactic body radiation therapy for recurrent nasopharyngeal carcinoma

Patient-Derived Nasopharyngeal Cancer Organoids for Disease Modeling and Radiation Dose Optimization

Measurement and comparison of head scatter factor for 7 MV unflattened (FFF) and 6 MV flattened photon beam using indigenously designed columnar mini phantom

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