Christelle D'Sa, Class of 2022
Radiation therapy is a common method used to help eradicate cancer cells in the body (7). It can be used to potentially eliminate cancer in its early stages or to keep cancerous tumors from coming back after surgery (4). For breast cancer specifically, there are two main types of radiation therapy: external beam radiation and internal radiation. External beam radiation involves a machine that is placed outside of the body. Depending on whether the patient has had a mastectomy or a breast-conserving surgery, the radiation will be concentrated on different areas of the chest. After a mastectomy the beam will be focused on the incision points and drainage points while after a breast-conserving surgery the beam will be focused mostly on the area where the tumor was excised (1). In contrast, internal radiation involves placing a device containing radioactive material inside the body. This type of radiation therapy is usually used for breast cancer in its early stages because the radiation is concentrated, so it minimizes the damage to the tissue surrounding the tumor (1). A new external radiation therapy machine called the 6-MV flattening-filter-free O-ring linear accelerator (6X-FFF OR) is being tested to see whether or not it is better in clinical settings than a traditional c-arm gantry.
C-arm gantries are commonly used in medical settings to help doctors guide a device into a patient. They are large machines with an arm that has a c-shaped attachment on the end. This c-shaped portion rotates around a person while beaming radiation and the machine then creates a picture of a person’s organs and where they are positioned. The accuracy of this picture increases when there is a smaller error in the 3D vector couch correction, which accounts for the error in the positioning of tissue in the image that was created. C-arm gantries are used in conjunction with an x-ray machine to allow a doctor to view a surgical instrument move through the body during surgery and can help administer minimally invasive surgeries (6).
Recently, research has been conducted to determine whether or not 6-MV flattening-filter-free O-ring linear accelerator (6X-FFF OR) technology can provide radiation therapy with less consequences than C-arm gantries, which are currently the most commonly used technology in clinical settings. The benefits to using 6X-FFF OR are that it provides a more focused beam that will better contain the radiation to a specific area of tissue and is quicker to use, which could in turn reduce the overall time the radiation therapy takes and increase the efficiency of the radiation therapy (3). The 6X-FFF OR also rotates around the patient faster, which creates a clearer picture of the tissue and its surroundings. Specifically in breast cancer treatments, this allows doctors to more clearly pinpoint the location of a tumor and focus the beam radiation at that point.
The research team found women who had recently done either a mastectomy or lumpectomy and then received radiation therapy to the breast or chest wall using 6X-FFF OR. Researchers then collected the womens' clinicopathological information, radiation therapy details, acute toxicities, dose-volume histogram data, couch corrections, and treatment times (2).
From this data the researchers were able to determine that the most common acute toxicities resulting from the radiation therapy were fatigue and dermatitis and that the 3-D vector couch correction, the error in creating the breast tumor image, was 0.77 cm on average for the treatment with 6X-FFF OR. This means that 6X-FFF OR has a similar level of accuracy as a c-arm gantry. Researchers also found that treatment times using 6X-FFF OR were sometimes delayed because of software faults, interlocks requiring physics override, equipment-related delays, and time spent waiting for setup approval. By excluding these issues, the average treatment time per patient was less when using 6X-FFF OR versus a traditional c-arm gantry (2).
Overall, the 6X-FFF OR technology was able to successfully treat a wide variety of patients with breast cancer who undertook different treatment plans, such as radiation therapy administered to either breast in unilateral radiation treatment or both in bilateral radiation treatment. The shorter amount of time required to administer the treatment also suggests that this would be useful in busy clinics and for patients with time sensitive schedules. Many patients could also start their radiation therapy earlier as a result of the additional timeslots that would become available (2). This early treatment could reduce the spread of the cancer and the extent of metastasis to the surrounding organs and lymph nodes. This could potentially lead to more patients being admitted daily and offer them more options for scheduling their appointment.
References
C-arm gantries are commonly used in medical settings to help doctors guide a device into a patient. They are large machines with an arm that has a c-shaped attachment on the end. This c-shaped portion rotates around a person while beaming radiation and the machine then creates a picture of a person’s organs and where they are positioned. The accuracy of this picture increases when there is a smaller error in the 3D vector couch correction, which accounts for the error in the positioning of tissue in the image that was created. C-arm gantries are used in conjunction with an x-ray machine to allow a doctor to view a surgical instrument move through the body during surgery and can help administer minimally invasive surgeries (6).
Recently, research has been conducted to determine whether or not 6-MV flattening-filter-free O-ring linear accelerator (6X-FFF OR) technology can provide radiation therapy with less consequences than C-arm gantries, which are currently the most commonly used technology in clinical settings. The benefits to using 6X-FFF OR are that it provides a more focused beam that will better contain the radiation to a specific area of tissue and is quicker to use, which could in turn reduce the overall time the radiation therapy takes and increase the efficiency of the radiation therapy (3). The 6X-FFF OR also rotates around the patient faster, which creates a clearer picture of the tissue and its surroundings. Specifically in breast cancer treatments, this allows doctors to more clearly pinpoint the location of a tumor and focus the beam radiation at that point.
The research team found women who had recently done either a mastectomy or lumpectomy and then received radiation therapy to the breast or chest wall using 6X-FFF OR. Researchers then collected the womens' clinicopathological information, radiation therapy details, acute toxicities, dose-volume histogram data, couch corrections, and treatment times (2).
From this data the researchers were able to determine that the most common acute toxicities resulting from the radiation therapy were fatigue and dermatitis and that the 3-D vector couch correction, the error in creating the breast tumor image, was 0.77 cm on average for the treatment with 6X-FFF OR. This means that 6X-FFF OR has a similar level of accuracy as a c-arm gantry. Researchers also found that treatment times using 6X-FFF OR were sometimes delayed because of software faults, interlocks requiring physics override, equipment-related delays, and time spent waiting for setup approval. By excluding these issues, the average treatment time per patient was less when using 6X-FFF OR versus a traditional c-arm gantry (2).
Overall, the 6X-FFF OR technology was able to successfully treat a wide variety of patients with breast cancer who undertook different treatment plans, such as radiation therapy administered to either breast in unilateral radiation treatment or both in bilateral radiation treatment. The shorter amount of time required to administer the treatment also suggests that this would be useful in busy clinics and for patients with time sensitive schedules. Many patients could also start their radiation therapy earlier as a result of the additional timeslots that would become available (2). This early treatment could reduce the spread of the cancer and the extent of metastasis to the surrounding organs and lymph nodes. This could potentially lead to more patients being admitted daily and offer them more options for scheduling their appointment.
References
- American Cancer Society. 2019 Sep 18. Radiation for Breast Cancer. American Cancer Society. [accessed 2019 Nov 15]. https://www.cancer.org/cancer/breast-cancer/treatment/radiation-for-breast-cancer.html
- Barsky AR, Ogrady F, Kennedy C, Taunk NK, Dong L, Metz JM, Li T, Freedman GM. 2019. Initial Clinical Experience Treating Patients with Breast Cancer on a 6-MV Flattening-Filter-Free O-Ring Linear Accelerator. Advances in Radiation Oncology 4:571–578. [accessed 2019 Nov 14]. https://www.sciencedirect.com/science/article/pii/S2452109419300600
- Clark RM. 2019. A Guide for Creating Optimal Breast Plans Utilizing 6X-Flattening-Filter-Free Tangential Fields. AAMD CE Center. [accessed 2019 Nov 15]. https://edu.medicaldosimetry.org/education/catalog/detail.cfm?id=428
- Lu J-Y, Zheng J, Zhang W-Z, Huang B-T. 2016 Jan 6. Flattening Filter-Free Beams in Intensity-Modulated Radiotherapy and Volumetric Modulated Arc Therapy for Sinonasal Cancer. PloS one. [accessed 2019 Nov 15]. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4703390/
- Max Pixel. 2016. Free photo Breast Cancer Awareness Month Pink Ribbon Health - Max Pixel. Free photo Breast Cancer Awareness Month Pink Ribbon Health - Max Pixel. [accessed 2019 Nov 23]. https://www.maxpixel.net/Breast-Cancer-Awareness-Month-Pink-Ribbon-Health-3713632
- Reference. What Is a C-Arm Machine? Reference. [accessed 2019 Nov 15]. https://www.reference.com/health/c-arm-machine-6c447d888a55cad2
- Smith Y. 2019 Feb 26. Radiotherapy for Breast Cancer. News. [accessed 2019 Nov 15]. https://www.news-medical.net/health/Radiotherapy-for-Breast-Cancer.aspx
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