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Hematology/oncology Clinics of North... Dec 2019Proton therapy is a form of external beam radiotherapy that has several advantages over conventional photon (x-ray) radiotherapy. Protons are useful in 2 scenarios that... (Review)
Review
Proton therapy is a form of external beam radiotherapy that has several advantages over conventional photon (x-ray) radiotherapy. Protons are useful in 2 scenarios that apply to a large proportion of cancer patients: lack of exit dose allows for delivery of a therapeutic radiation dose to tumors in challenging anatomic locations, and reduction in integral dose (low-dose bath) to normal tissues that may reduce the risk of late toxicities and secondary cancers. The emergence of smaller, more economically viable single-room proton units has led to the expansion in use of this technology across the world.
Topics: Humans; Neoplasms; Organs at Risk; Proton Therapy; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted
PubMed: 31668216
DOI: 10.1016/j.hoc.2019.08.006 -
Advanced Drug Delivery Reviews Jan 2017In principle, proton therapy offers a substantial clinical advantage over conventional photon therapy. This is because of the unique depth-dose characteristics of... (Review)
Review
In principle, proton therapy offers a substantial clinical advantage over conventional photon therapy. This is because of the unique depth-dose characteristics of protons, which can be exploited to achieve significant reductions in normal tissue doses proximal and distal to the target volume. These may, in turn, allow escalation of tumor doses and greater sparing of normal tissues, thus potentially improving local control and survival while at the same time reducing toxicity and improving quality of life. Protons, accelerated to therapeutic energies ranging from 70 to 250MeV, typically with a cyclotron or a synchrotron, are transported to the treatment room where they enter the treatment head mounted on a rotating gantry. The initial thin beams of protons are spread laterally and longitudinally and shaped appropriately to deliver treatments. Spreading and shaping can be achieved by electro-mechanical means to treat the patients with "passively-scattered proton therapy" (PSPT) or using magnetic scanning of thin "beamlets" of protons of a sequence of initial energies. The latter technique can be used to treat patients with optimized intensity modulated proton therapy (IMPT), the most powerful proton modality. Despite the high potential of proton therapy, the clinical evidence supporting the broad use of protons is mixed. It is generally acknowledged that proton therapy is safe, effective and recommended for many types of pediatric cancers, ocular melanomas, chordomas and chondrosarcomas. Although promising results have been and continue to be reported for many other types of cancers, they are based on small studies. Considering the high cost of establishing and operating proton therapy centers, questions have been raised about their cost effectiveness. General consensus is that there is a need to conduct randomized trials and/or collect outcomes data in multi-institutional registries to unequivocally demonstrate the advantage of protons. Treatment planning and plan evaluation of PSPT and IMPT require special considerations compared to the processes used for photon treatment planning. The differences in techniques arise from the unique physical properties of protons but are also necessary because of the greater vulnerability of protons to uncertainties, especially from inter- and intra-fractional variations in anatomy. These factors must be considered in designing as well as evaluating treatment plans. In addition to anatomy variations, other sources of uncertainty in dose delivered to the patient include the approximations and assumptions of models used for computing dose distributions for planning of treatments. Furthermore, the relative biological effectiveness (RBE) of protons is simplistically assumed to have a constant value of 1.1. In reality, the RBE is variable and a complex function of the energy of protons, dose per fraction, tissue and cell type, end point, etc. These uncertainties, approximations and current technological limitations of proton therapy may limit the achievement of its true potential. Ongoing research is aimed at better understanding the consequences of the various uncertainties on proton therapy and reducing the uncertainties through image-guidance, adaptive radiotherapy, further study of biological properties of protons and the development of novel dose computation and optimization methods. However, residual uncertainties will remain in spite of the best efforts. To increase the resilience of dose distributions in the face of uncertainties and improve our confidence in dose distributions seen on treatment plans, robust optimization techniques are being developed and implemented. We assert that, with such research, proton therapy will be a commonly applied radiotherapy modality for most types of solid cancers in the near future.
Topics: Humans; Neoplasms; Proton Therapy; Quality of Life; Radiotherapy Planning, Computer-Assisted
PubMed: 27919760
DOI: 10.1016/j.addr.2016.11.006 -
International Journal of Molecular... Sep 2020FLASH radiotherapy is the delivery of ultra-high dose rate radiation several orders of magnitude higher than what is currently used in conventional clinical... (Review)
Review
FLASH radiotherapy is the delivery of ultra-high dose rate radiation several orders of magnitude higher than what is currently used in conventional clinical radiotherapy, and has the potential to revolutionize the future of cancer treatment. FLASH radiotherapy induces a phenomenon known as the FLASH effect, whereby the ultra-high dose rate radiation reduces the normal tissue toxicities commonly associated with conventional radiotherapy, while still maintaining local tumor control. The underlying mechanism(s) responsible for the FLASH effect are yet to be fully elucidated, but a prominent role for oxygen tension and reactive oxygen species production is the most current valid hypothesis. The FLASH effect has been confirmed in many studies in recent years, both and , with even the first patient with T-cell cutaneous lymphoma being treated using FLASH radiotherapy. However, most of the studies into FLASH radiotherapy have used electron beams that have low tissue penetration, which presents a limitation for translation into clinical practice. A promising alternate FLASH delivery method is via proton beam therapy, as the dose can be deposited deeper within the tissue. However, studies into FLASH protons are currently sparse. This review will summarize FLASH radiotherapy research conducted to date and the current theories explaining the FLASH effect, with an emphasis on the future potential for FLASH proton beam therapy.
Topics: Humans; Neoplasms; Proton Therapy; Protons; Radiotherapy; Radiotherapy Dosage; Reactive Oxygen Species
PubMed: 32899466
DOI: 10.3390/ijms21186492 -
The British Journal of Radiology Mar 2022Localized prostate cancer can be treated with several radiotherapeutic approaches. Proton therapy (PT) can precisely target tumors, thus sparing normal tissues and... (Review)
Review
OBJECTIVE
Localized prostate cancer can be treated with several radiotherapeutic approaches. Proton therapy (PT) can precisely target tumors, thus sparing normal tissues and reducing side-effects without sacrificing cancer control. However, PT is a costly treatment compared with conventional photon radiotherapy, which may undermine its overall efficacy. In this review, we summarize current data on the dosimetric rationale, clinical benefits, and cost of PT for prostate cancer.
METHODS
An extensive literature review of PT for prostate cancer was performed with emphasis on studies investigating dosimetric advantage, clinical outcomes, cost-effective strategies, and novel technology trends.
RESULTS
PT is safe, and its efficacy is comparable to that of standard photon-based therapy or brachytherapy. Data on gastrointestinal, genitourinary, and sexual function toxicity profiles are conflicting; however, PT is associated with a low risk of second cancer and has no effects on testosterone levels. Regarding cost-effectiveness, PT is suboptimal, although evolving trends in radiation delivery and construction of PT centers may help reduce the cost.
CONCLUSION
PT has several advantages over conventional photon radiotherapy, and novel approaches may increase its efficacy and safety. Large prospective randomized trials comparing photon therapy with proton-based treatments are ongoing and may provide data on the differences in efficacy, toxicity profile, and quality of life between proton- and photon-based treatments for prostate cancer in the modern era.
ADVANCES IN KNOWLEDGE
PT provides excellent physical advantages and has a superior dose profile compared with X-ray radiotherapy. Further evidence from clinical trials and research studies will clarify the role of PT in the treatment of prostate cancer, and facilitate the implementation of PT in a more accessible, affordable, efficient, and safe way.
Topics: Cost-Benefit Analysis; Forecasting; Humans; Male; Prostatic Neoplasms; Proton Therapy; Radiotherapy Dosage
PubMed: 34558308
DOI: 10.1259/bjr.20210670 -
The British Journal of Radiology Mar 2020
Topics: Humans; Neoplasms; Proton Therapy
PubMed: 32081045
DOI: 10.1259/bjr.20209004 -
Seminars in Radiation Oncology Jan 2018Because of its sharp lateral penumbra and steep distal fall-off, proton therapy offers dosimetric advantages over photon therapy. In head and neck cancer, proton therapy... (Review)
Review
Because of its sharp lateral penumbra and steep distal fall-off, proton therapy offers dosimetric advantages over photon therapy. In head and neck cancer, proton therapy has been used for decades in the treatment of skull-base tumors. In recent years the use of proton therapy has been extended to numerous other disease sites, including nasopharynx, oropharynx, nasal cavity and paranasal sinuses, periorbital tumors, skin, and salivary gland, or to reirradiation. The aim of this review is to present the physical properties and dosimetric benefit of proton therapy over advanced photon therapy; to summarize the clinical benefit described for each disease site; and to discuss issues of patient selection and cost-effectiveness.
Topics: Cost-Benefit Analysis; Head and Neck Neoplasms; Humans; Patient Selection; Proton Therapy; Radiotherapy Dosage
PubMed: 29173756
DOI: 10.1016/j.semradonc.2017.08.004 -
Current Treatment Options in Oncology May 2018The application of proton beam radiation therapy in the treatment of head and neck cancer has grown tremendously in the past few years. Globally, widespread interest in... (Review)
Review
The application of proton beam radiation therapy in the treatment of head and neck cancer has grown tremendously in the past few years. Globally, widespread interest in proton beam therapy has led to multiple research efforts regarding its therapeutic value and cost-effectiveness. The current standard of care using modern photon radiation technology has demonstrated excellent treatment outcomes, yet there are some situations where disease control remains suboptimal with the potential for detrimental acute and chronic toxicities. Due to the advantageous physical properties of the proton beam, proton beam therapy may be superior to photon therapy in some patient subsets for both disease control and patient quality of life. As enthusiasm and excitement for proton beam therapy continue to increase, clinical research and widespread adoption will elucidate the true value of proton beam therapy and give a greater understanding of the full risks and benefits of proton therapy in head and neck cancer.
Topics: Head and Neck Neoplasms; Humans; Proton Therapy; Radiotherapy Planning, Computer-Assisted; Recurrence; Retreatment; Treatment Outcome
PubMed: 29744681
DOI: 10.1007/s11864-018-0546-9 -
Chinese Clinical Oncology Aug 2016Relative to conventional photon irradiation, proton therapy has distinct advantages in its ability to more precisely target tumor while shielding adjacent normal... (Review)
Review
Relative to conventional photon irradiation, proton therapy has distinct advantages in its ability to more precisely target tumor while shielding adjacent normal tissues. In the setting of skull base tumors, proton therapy plays a critical role in the dose-escalation required for optimal tumor control of chordomas, chondrosarcomas, and malignancies of the paranasal sinuses and nasal cavity. For benign tumors such as craniopharyngiomas, pituitary adenomas and meningiomas, proton therapy can limit long-term adverse effects, such as secondary malignancies. This review summarizes published literature to date regarding the role of proton therapy in skull base tumors and introduces emerging proton therapy approaches such as pencil-beam scanning (PBS).
Topics: Humans; Proton Therapy; Skull; Skull Base Neoplasms
PubMed: 27558252
DOI: 10.21037/cco.2016.07.05 -
Cancer Communications (London, England) Oct 2019Proton therapy offers dominant advantages over photon therapy due to the unique depth-dose characteristics of proton, which can cause a dramatic reduction in normal... (Review)
Review
Proton therapy offers dominant advantages over photon therapy due to the unique depth-dose characteristics of proton, which can cause a dramatic reduction in normal tissue doses both distal and proximal to the tumor target volume. In turn, this feature may allow dose escalation to the tumor target volume while sparing the tumor-neighboring susceptible organs at risk, which has the potential to reduce treatment toxicity and improve local control rate, quality of life and survival. Some dosimetric studies in various cancers have demonstrated the advantages over photon therapy in dose distributions. Further, it has been observed that proton therapy confers to substantial clinical advantage over photon therapy in head and neck, breast, hepatocellular, and non-small cell lung cancers. As such, proton therapy is regarded as the standard modality of radiotherapy in many pediatric cancers from the technical point of view. However, due to the limited clinical evidence, there have been concerns about the high cost of proton therapy from an economic point of view. Considering the treatment expenses for late radiation-induced toxicities, cost-effective analysis in many studies have shown that proton therapy is the most cost-effective option for brain, head and neck and selected breast cancers. Additional studies are warranted to better unveil the cost-effective values of proton therapy and to develop newer ways for better protection of normal tissues. This review aims at reviewing the recent studies on proton therapy to explore its benefits and cost-effectiveness in cancers. We strongly believe that proton therapy will be a common radiotherapy modality for most types of solid cancers in the future.
Topics: Cost-Benefit Analysis; Humans; Neoplasms; Proton Therapy
PubMed: 31640788
DOI: 10.1186/s40880-019-0407-3 -
World Journal of Gastroenterology Jul 2018Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death, as few patients can be treated with currently available curative local modalities. In... (Review)
Review
Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death, as few patients can be treated with currently available curative local modalities. In patients with HCC where curative modalities are not feasible, radiation therapy (RT) has emerged as an alternative or combination therapy. With the development of various technologies, RT has been increasingly used for the management of HCC. Among these advances, proton beam therapy (PBT) has several unique physical properties that give it a finite range in a distal direction, and thus no exit dose along the beam path. Therefore, PBT has dosimetric advantages compared with X-ray therapy for the treatment of HCC. Indeed, various reports in the literature have described the favorable clinical outcomes and improved safety of PBT for HCC patients compared with X-ray therapy. However, there are some technical issues regarding the use of PBT in HCC, including uncertainty of organ motion and inaccuracy during calculation of tissue density and beam range, all of which may reduce the robustness of a PBT treatment plan. In this review, we discuss the physical properties, current clinical data, technical issues, and future perspectives on PBT for the treatment of HCC.
Topics: Carcinoma, Hepatocellular; DNA Damage; Digestive System; Humans; Liver Neoplasms; Proton Therapy; Radiation Injuries; Radiometry; Radiotherapy Dosage; Treatment Outcome
PubMed: 30065555
DOI: 10.3748/wjg.v24.i28.3090