Limits...
Technical advances and pitfalls in head and neck radiotherapy.

Parvathaneni U, Laramore GE, Liao JJ - J Oncol (2012)

Bottom Line: However, these benefits come with a serious and sobering price.Proton therapy has a theoretical physical advantage over photon therapy due to a lack of "exit dose".The purpose of this article is to review the literature, discuss the salient issues and make recommendations that address the gaps in knowledge.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of Washington, Seattle, WA 98195, USA.

ABSTRACT
Intensity Modulated Radiotherapy (IMRT) is the standard of care in the treatment of head and neck squamous cell carcinomas (HNSCC) based on level 1 evidence. Technical advances in radiotherapy have revolutionized the treatment of HNSCC, with the most tangible gain being a reduction in long term morbidity. However, these benefits come with a serious and sobering price. Today, there is a greater chance of missing the target/tumor due to uncertainties in target volume definition by the clinician that is demanded by the highly conformal planning process involved with IMRT. Unless this is urgently addressed, our patients would be better served with the historically practiced non conformal radiotherapy, than IMRT which promises lesser morbidity. Image guided radiotherapy (IGRT) ensures the level of set up accuracy warranted to deliver a highly conformal treatment plan and should be utilized with IMRT, where feasible. Proton therapy has a theoretical physical advantage over photon therapy due to a lack of "exit dose". However, clinical data supporting the routine use of this technology for HNSCC are currently sparse. The purpose of this article is to review the literature, discuss the salient issues and make recommendations that address the gaps in knowledge.

No MeSH data available.


Related in: MedlinePlus

Depth dose curves for a 6 MV photon beam (solid line), a 170 MeV proton beam (dashed line), and a 330 MeV/amu carbon ion beam (dotted line) as a function of depth in a water phantom. The beams have been arbitrarily normalized to 100 at their maxima.
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fig5: Depth dose curves for a 6 MV photon beam (solid line), a 170 MeV proton beam (dashed line), and a 330 MeV/amu carbon ion beam (dotted line) as a function of depth in a water phantom. The beams have been arbitrarily normalized to 100 at their maxima.

Mentions: Unlike photon beams, charged particle beams have sharp cutoffs in their range due to the intrinsic physical principles underlying their interactions with matter. They deposit little energy until they near the end of their range at which point the rate of energy loss increases resulting in what is termed a Bragg peak. Figure 5 shows the energy loss in water for a typical megavoltage X-ray beam used in therapy, a proton beam, and a carbon ion beam with energies set to place the Bragg peaks at about a 20 cm depth in water. For practical clinical purposes, protons have the same biological properties as photon beams, apart from a small scaling factor of 1.1, which is taken to be the same for all tissues [49]. This ignores a very small region at the distal edge of the Bragg peak where increased linear energy transfer (LET) theoretically should result in an increase in relative biological effectiveness (RBE). For heavier ions such as carbon, the high LET along their path gives rise to higher RBEs, similar to fast neutrons, which are both tissue and dose regimen dependent. While the lateral beam edge is sharper for C-ions than for protons, fragmentation effects give rise to a “tail” at the distal edge of its Bragg peak.


Technical advances and pitfalls in head and neck radiotherapy.

Parvathaneni U, Laramore GE, Liao JJ - J Oncol (2012)

Depth dose curves for a 6 MV photon beam (solid line), a 170 MeV proton beam (dashed line), and a 330 MeV/amu carbon ion beam (dotted line) as a function of depth in a water phantom. The beams have been arbitrarily normalized to 100 at their maxima.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369487&req=5

fig5: Depth dose curves for a 6 MV photon beam (solid line), a 170 MeV proton beam (dashed line), and a 330 MeV/amu carbon ion beam (dotted line) as a function of depth in a water phantom. The beams have been arbitrarily normalized to 100 at their maxima.
Mentions: Unlike photon beams, charged particle beams have sharp cutoffs in their range due to the intrinsic physical principles underlying their interactions with matter. They deposit little energy until they near the end of their range at which point the rate of energy loss increases resulting in what is termed a Bragg peak. Figure 5 shows the energy loss in water for a typical megavoltage X-ray beam used in therapy, a proton beam, and a carbon ion beam with energies set to place the Bragg peaks at about a 20 cm depth in water. For practical clinical purposes, protons have the same biological properties as photon beams, apart from a small scaling factor of 1.1, which is taken to be the same for all tissues [49]. This ignores a very small region at the distal edge of the Bragg peak where increased linear energy transfer (LET) theoretically should result in an increase in relative biological effectiveness (RBE). For heavier ions such as carbon, the high LET along their path gives rise to higher RBEs, similar to fast neutrons, which are both tissue and dose regimen dependent. While the lateral beam edge is sharper for C-ions than for protons, fragmentation effects give rise to a “tail” at the distal edge of its Bragg peak.

Bottom Line: However, these benefits come with a serious and sobering price.Proton therapy has a theoretical physical advantage over photon therapy due to a lack of "exit dose".The purpose of this article is to review the literature, discuss the salient issues and make recommendations that address the gaps in knowledge.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of Washington, Seattle, WA 98195, USA.

ABSTRACT
Intensity Modulated Radiotherapy (IMRT) is the standard of care in the treatment of head and neck squamous cell carcinomas (HNSCC) based on level 1 evidence. Technical advances in radiotherapy have revolutionized the treatment of HNSCC, with the most tangible gain being a reduction in long term morbidity. However, these benefits come with a serious and sobering price. Today, there is a greater chance of missing the target/tumor due to uncertainties in target volume definition by the clinician that is demanded by the highly conformal planning process involved with IMRT. Unless this is urgently addressed, our patients would be better served with the historically practiced non conformal radiotherapy, than IMRT which promises lesser morbidity. Image guided radiotherapy (IGRT) ensures the level of set up accuracy warranted to deliver a highly conformal treatment plan and should be utilized with IMRT, where feasible. Proton therapy has a theoretical physical advantage over photon therapy due to a lack of "exit dose". However, clinical data supporting the routine use of this technology for HNSCC are currently sparse. The purpose of this article is to review the literature, discuss the salient issues and make recommendations that address the gaps in knowledge.

No MeSH data available.


Related in: MedlinePlus