Radiotherapy
In Malta, cancer represents a significant burden of disease, with 1 in 4 individuals being diagnosed with cancer by the age of 80 years. In 2016, 27% of all deaths locally were attributed to cancer (World Health Organisation, 2018). Approximately 50% of all patients diagnosed with cancer will receive radiotherapy as part of their treatment (Delaney, Jacob, Featherstone, & Barton, 2005). Therefore, radiotherapy represents a crucial part of cancer treatment, in conjunction with other therapies such as surgery and chemotherapy.
The discovery of X-rays over 100 years ago has allowed for numerous advances in technology and in the treatment of diseases. The use of radiation in medicine is not a new concept, however, only relatively recently has radiotherapy become an accepted, well-established therapy in the treatment of diseases such as cancer (Martins, 2018). Radiotherapy may be defined as the delivery of ionising radiation to a target in order to treat disease. It encompasses a wide range of treatment types and techniques, which have gradually developed throughout history with the advancement of new technologies (Martins, 2018).
Types of Radiotherapy Treatments
Briefly, radiotherapy treatments may be classified as external beam radiotherapy (EBRT), which is the most frequently utilised type, or internal radiotherapy. In EBRT the source of ionising radiation is located outside the patient’s body, typically delivered through a linear accelerator (LINAC) or similar units. Conversely, in internal radiotherapy, the source of ionising radiation is placed inside the patient’s body. The type of ionising radiation used is most commonly x-ray photons, where these particles are accelerated and targeted to the localised disease. However, other particles such as electrons or protons may be used to achieve the therapeutic effect. The radiotherapy technique used is dependent on the tumour site, disease characteristics (i.e. stage, grade and histology) and the patient’s overall fitness to receive the treatment. Treatment intent may be curative or palliative, which focuses on reducing the disease burden for the patient.
Radiobiology
Irrespective of the radiotherapy technique used, ionising radiation is utilised to damage diseased cells, while minimising the damage to the healthy tissues. Damage to healthy tissues will lead to the development of radiation associated side effects, such as skin erythema, dry desquamation, and fatigue (Beyzadeoglu, Ozyigit, & Ebruli, 2010).
Two pathways are responsible for the therapeutic effect of radiotherapy. The direct pathway occurs by directly depositing the energy from the ionising radiation, thereby resulting in cellular damage through ionisation. Conversely, the indirect pathway generates free radicals, most frequently from the water. This in turn leads to cellular damage and is responsible for the majority of the cellular damage in radiotherapy treatments. (Cherry & Duxbury, 2019), (Figure 1) In order for ionisation to lead to cell death, the damage must occur within the deoxyribonucleic acid (DNA) macromolecule of the cell. Moreover, several types of DNA damage may occur, which may be repaired by the cell. However, one type of damage termed “double-strand break” is frequently irreparable, thereby leading to apoptosis or mitotic catastrophe of the affected cell. (Cherry & Duxbury, 2019)
Illustration of DNA radiation damage (Retrieved from: Pocket Dentistry, 2015)
Overview of the Treatment Pathway
In Malta, all radiotherapy treatments take place at the Sir Anthony Mamo Oncology Centre (SAMOC). The treatment pathway may vary between centres; however most follow a standardised procedure. Figure 2 illustrates the key stages of radiotherapy treatments (The Society and College of Radiographers, 2020).
Radiotherapy Pathway
Prior to the localisation scan, which is performed using a dedicated computed tomography (CT) scanner, the patient is first provided an overview of the process and what he/she should expect. Similarly, this is done prior to starting the first radiotherapy treatment. The immobilisation is primarily used to minimise patient motion during irradiation and to allow for reproducible setups. In addition, throughout the radiotherapy treatment period, the patient is scheduled to meet with radiotherapy specialised nurses and the oncologist. During these sessions, any side-effects and issues may be addressed. The radiotherapy treatments are delivered on one of three LINACs present at SAMOC. Treatments are led by radiographers; however, radiotherapy requires a multidisciplinary approach, including without limitation: psychologists, occupational therapists and physiotherapists.
Radiotherapy Contraindications
Although radiotherapy treatments are widely used for several cancer types, the use of radiotherapy may be contraindicated in certain clinical scenarios. This may be due to the treatment being inappropriate for the disease characteristics or as it may compromise patient safety. The following are the most frequent relative contraindications for radiotherapy (Beyzadeoglu et al., 2010):
Treatment of radiation-insensitive lesions, such as soft tissue sarcomas;
Poor performance status prior to initiation radiotherapy;
Severe weight changes and/or cachexia associated with the lesion;
Development of complications associated with the lesion, such as large-volume ascites, plural effusions or bowel perforation;
Development of severe radiation-associated toxicities.
Nonetheless, in specific cases radiotherapy may still be used in the presence of these contraindications, with alterations in the treatment plan and appropriate precautions. Radiotherapy may also be stopped should such factors develop, since they may compromise the patient’s safety and quality of life.
Furthermore, radiotherapy is a loco-regional treatment, where the therapeutic effect is focused on the target area. This is as opposed to other cancer treatments such as chemotherapy or immunotherapy, which are systemic therapies. Therefore, although metastasis is routinely treated using radiotherapy, the intent of treatment is palliation and not curative.
Future Developments
The development of novel radiotherapy techniques allows for greater treatment accuracy, shorter treatment times and fewer radiation-associated side-effects. This thereby improves the efficacy of treatments and quality of life. At SAMOC, such new techniques are gradually being introduced. One such example is volume modulated arc therapy (VMAT), which was adopted locally in February 2017. Currently, VMAT has become the standard technique for several cancers, such as prostate cancer. Another recent advancement is the implementation of 4D CT scanning, which allows respiratory motion to be taken into account when planning treatments.
In conclusion, radiotherapy has a significant role in cancer treatment, where techniques may be utilised for treatment delivery depending on the clinical scenario. In Malta, radiotherapy is well established, with future advancements allowing local treatments to be improved further.
References
Beyzadeoglu, M., Ozyigit, G., & Ebruli, C. (2010). Radiobiology - chapter 2. In Springer (Ed.), Basic radiation oncology (2010th ed., ) Springer.
Cherry, P., & Duxbury, A., M. (2019). In Cherry P., Duxbury A. (Eds.), Practical radiotherapy physics and equipment (Third ed.). London: John Wiley & Sons.
Delaney, G., Jacob, S., Featherstone, C., & Barton, M. (2005). The role of radiotherapy in cancer treatment estimating optimal utilization from a review of evidence-based clinical guidelines. Cancer, 104(6), 1129-1137.
Martins, P., Nuno. (2018). A brief history about radiotherapy. International Journal of Latest Research in Engineering and Technology, 4(2), 8-11.
Pocket Dentistry. (2015). The biological effects associated with X-rays, risk and practical radiation protection. Retrieved 04/04, 2020, from https://pocketdentistry.com/5-the-biological-effects-associated-with-x-rays-risk-and-practical-radiation-protection/
The Society and College of Radiographers. (2020). An overview of radiotherapy. Retrieved 04/04, 2020, from https://www.sor.org/public-and-patient/overview-radiotherapy
World Health Organisation. (2018). Noncommunicable diseases country profiles 2018 No. 3)World Health Organisation.
Written by: Robert Pisani