Abstract:
The purpose of this study is to provide a comparative analysis in the performance of the LINAC and Proton therapy for Head and neck cancer. The study analyzes the precision, effect on surrounding organs, side-effects, quality or patient life, cost and accessibility of the technology. The results found weigh towards better efficiency of Proton therapy with a few counterpoints that are discussed in the paper. The paper also expands on the recent development in both the technologies and stresses on the increase in use of Proton therapy world wide.
Thesis statement:
Despite being costly and having low patient volume, Proton therapy is more efficient than LINAC for treating Head and neck cancer due to its precision, less damage to surrounding tissues and less side effects on the patient.
Introduction:
Radiation therapy has been one of the most efficient ways of cancer treatment, allowing for improved quality of life for cancer patients. However with the global trends indicating increase in the number of cancer cases world wide. 20 million new cancer cases were projected in 2024, with head and neck cancer contributing significantly to the burden. This brings a pressing question into light, what is the most efficient treatment in radiation therapy?The purpose of this paper is to provide a comparative analysis between LINAC and Proton therapy (PT), two leading radiation therapies for the treatment of head and neck cancer (HNC) by comparing factors like accuracy, effect on normal tissues, side effects, cost and accessibility. The paper brings awareness to increase the use of proton therapy and also
expands on the significant advancements made to both the LINAC and Proton therapy. This study combines the usage of primary and secondary sources to elaborate on the objectives.
Literature review:
In this paper, the literature is structured to provide experimental evidence like the investigation published in 2008 by Resto et al. involving 102 patients showed the success of PT in treating HNC and A study done by Dr. Baumann and his colleagues analyzed the data of 1500 adults receiving chemotherapy and radiation between 2011-2016. The paper then combines previous research works and comments by experts at Cytecare hospital to bring out the overall comparison and analysis.
Research & Analysis:
(1) Accuracy
LINAC is a device that uses high energy x-rays or electrons to treat cancer. The device accelerates electrons to produce high energy beams that are directed towards a mapped tumor site. The LINAC is capable of mapping and generating the shape of the tumor to minimize damage. However the X-ray beams still damage a certain area of surrounding tissue especially the ones located at the dorsal side of the tumor. Some of the radiation energy is absorbed by normal organs.
In the case of PT, the proton energy is accelerated to a point where the energy is sufficient to reach the distal edge of the tumor with the help of cyclotrons and synchrotrons. The Bragg peak property of the proton, allows it to penetrate through normal tissues and release maximum amount of energy at the end of the beam at the target location and then disappears instantly instead of being absorbed by the surrounding tissues.
Fig(1)- comparison of precision of PT and LINAC
In the case of HNC, qualitatively, the most efficient system should have high accuracy and minimum damage to surrounding tissue, due to the presence of vital organs like the brain. Quantitatively, an investigation published in 2008 by Resto et al. involving 102 patients showed the success of PT in treating HNC. The basic rubric of comparison you can take is the Conformity Index (CI)* . As per summarized data
CI=Tv*Ptv
CI=Treated volume* Planning target volume
(LINAC- )
Average CI= 1.2
Standard deviation= 0.1
(Proton therapy- )
Average CI= 1.1
Standard deviation= 0.05
P-value<0.05, this suggests that Proton therapy has a better CI than LINAC making it far more accurate and effective for treating delicate structures such as the HNC.
*Conformity index= Measures how well the radiation dose conforms to the target volume
(2) Dose to Organs at Risk & Side effects
Due to the Bragg Peak property of the Proton the damage to surrounding tissues is significantly less as compared to LINAC. By the NTCP (Normal tissue complication probability) specifically for HNC we get the following data-
(LINAC)
Dose- 60 Gy
D50-65 Gy
m- 0.35
(Proton therapy)
Dose-45 Gy
D50- 65 Gy
m-0.35
LINAC NTCP= 41.3%
Proton Therapy= 18.9%
PT has a lower NTCP for HNC demonstrating lower risks to surrounding structures making it more efficient for treatment.
Fig(2)- comparison of effect on surrounding organs by LINAC (left) and Proton therapy (right)
With lower NTCP, this also decreases the level of side-effects and increases the quality of life of the patient. Since the side-effects of HNC treatment can be quite jarring ranging from lymphoedema to issues in swallowing and speaking.
A study done by Dr. Baumann and his colleagues analyzed the data of 1500 adults receiving chemotherapy and radiation between 2011-2016. 400 received PT experienced fewer serious side effects as compared to traditional X-rays. PT also did not hinder a patient's ability to perform routine activities as much as traditional radiation.
(3) Cost and Set up
The LINAC equipment costs approximately 10-25 crores which is topped up with installation, infrastructure and maintenance costs. Additionally the LINAC requires a bunker design to allow safe escape of radiation
Fig(3)- Radio bunker therapy design
The LINAC also receives high patient volume due to cost-effectiveness and accessibility. Compared to the LINAC the PT is very costly with its equipment costing 300-500 crores topped with additional costs. The PT has also comparatively high electricity usage and requires an expert team to operate it. This is the primary reason for the low volume of patients for the PT. However, considering its significance and efficiency as compared to traditional rays, PT should be used more for cancer treatments especially for HNC which has many vital organs at risk.
(4) Advancements
The most recent advancement to the LINAC is the Reflexion system approved in 2021- to utilize PET scanners in the integrated image guidance system to give better accuracy when treating patients. A specific advancement in PT for HNC is the Pencil beam scanning to treat tumors with unparalleled precision. The technique adds a field mirroring the tumor's shape and the beam can be released with the precision of a few millimeters wide (width of a pencil). This advancement is very significant to treat complex cancers like HNC.
Conclusion:
Proton therapy is a far more efficient way for the treatment of HNC in terms of its precision, side-effects and the effect on surrounding tissues. Cost and accessibility are certain counter points to the efficiency of the PT however there is nothing that can rival its technological efficiency and the quality of life that it provides to the patient. The investment in fact will provide a far greater output than the commonly used LINAC. Advancements in PT such as the Pencil beam scanning technique add to its efficiency. PT should be further advocated for HNC and other complex cancer treatments.
Acknowledgement:
I would like to thank Mr.Amit for giving me an opportunity to undergo an observership at Cytecare cancer hospital Bangalore, which has allowed me to put forward this manuscript today. I would also like to extend my gratitude to Dr. Anand for his explanation and analysis on the LINAC radio- bunker therapy. Lastly, I would like to thank my mentor Ms. Kate Kauffman for her constant support and guidance in the completion of the manuscript.
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