An introduction to HDR Brachytherapy
In Canada, prostate cancer is the most common cancer for males, and it is the fourth most common cancer of all people. Surgery is the most widespread way of treating prostate cancer. However, it is an invasive strategy that requires excessive openings on the patient’s body and may lead to pain, fatigue, or sexual disabilities. In recent years, radiotherapy has been accepted as a substitution for traditional prostate cancer treatments. High Dose Rate brachytherapy is a new way of prostate cancer treatment using gamma radiation to damage cancer cells. It has many advantages over other types of radiotherapy and surgery treatments for prostate cancer. Meanwhile, HDR brachytherapy still has long-term success rates, side effects, and social problems for the patients.
High Dose Rate brachytherapy(HDR brachytherapy) is a kind of radiation cancer treatment that involves inserting radioactive materials internally into the patient’s body. Unlike Low Dose Rate brachytherapy, the radioactive materials only stay inside the patient’s body for short periods of time(usually less than twenty minutes) instead of permanently staying inside the patient’s body. HDR brachytherapy can be used as a treatment itself, and it is also commonly used together with External Beam Radiation Therapy(EBRT). The inserted radioactive material mainly targets splitting cancer cells, helping to slow or stop the unhealthy cells' spread and duplication. The principle behind this is that during the life cycle of any cell, the process is being classified into five phases: G0, G1, S, G2, M. During each of these phases, the likelihood of the cell being damaged is different. Radiosensitivity is a term used to describe this. During the M phases(Mitosis phase), where the cell division happens, a cell has the highest radiosensitivity, meaning that the radioactive materials are most likely to cause higher amounts of damage to these cells. Cancer cells in other states will also be affected with less damage. Radiation released by the radioactive insertion damaged the genes(DNA) in cells that control the growth and split. Once the genes inside a cell were damaged, the cells can no longer complete these two processes, causing the cell to die eventually. Cancer cells that were damaged usually die in a few days or weeks.
The most common radioactive material used in HDR brachytherapy is Iridium 192, with a half-life of 73.8 days. During 95% of its decay, Iridium 182 decays into Platinum 182 through beta decay(77192Ir → -10e + 78192Pt). The other 5% of the time, it decays into Osmium 192 through electron capture(77192Ir + -10e → 76192Os). Meanwhile, it releases gamma radiation, which serves as a weapon to damage cancer cells. Iridium 192 forms a special decay pattern involving 29 gamma radiation emission peaks from 0.110 to 1.378 MeV. In a brachytherapy process, doctors will first visualize the tumour inside the patient’s body using ultrasound, computed axial tomography, or x-ray radiography. Using this information, doctors will choose the right radioactive materials and their dose and order them. After this step, doctors will insert these radioactive materials into a capsule called the applicator. Applicators can be needles, tubes, wires, or nuclear seeds. Once the applicator is made, doctors commonly use an “after loading” technique by an “after loader.” The applicator is put inside the “after loader” and delivered inside the patient’s body using tubes. After certain amounts of time, the applicator will return through the guide tube.
Compared to LDR brachytherapy, HDR brachytherapy has its strengths and weaknesses. Firstly, in HDR brachytherapy, radioactive insertions were all taken out after the treatment, leaving nothing inside. In LDR brachytherapy, these materials often stay permanently inside the patient’s body, causing a higher risk of other side effects. Secondly, studies found that “LDR prostate brachytherapy was associated with significantly better relapse and serious adverse event profile than HDR brachytherapy when combined with External Beam Radiation Therapy (EBRT). ”(Casey Gray and Kaitryn Campbell, 2019). This proves that HDR has better long-term results in comparison to LDR brachytherapy when used together with other kinds of radiotherapy. One disadvantage of HDR brachytherapy is that it is not suitable for patients that seek active treatments. Since HDR brachytherapy releases higher amounts of radiation, the process is fast and harder to control, increasing the chance of accidentally damaging healthy cells. In contrast, LDR brachytherapy only delivers lower amounts of radiation. To sum up, HDR and LDR have their respective benefits. However, research shows that “There is not currently direct clinical evidence supporting the superiority of HDR or LDR brachytherapy concerning tumour control or reduced toxicity.” The selection of HDR or LDR brachytherapy needs to depend on the specific circumstance of the patients.
HDR brachytherapy also has advantages over traditional surgery treatment methods. To begin with, unlike surgery, HDR brachytherapy doesn’t involve excessive openings on the patient’s body. This prevents the patient from having a large surgical cut or experiencing pain and fatigue. The recovery time is also significantly shorter since cancer surgery patients need 1 month to 9 months to recover. In contrast, patients who undergo HDR brachytherapy can recover in less than five days or even immediately after the treatment. Secondly, HDR brachytherapy is more precise than surgery. HDR brachytherapy is controlled and processed by computers. On the contrary, prostate cancer surgery is done by humans manually. This means that surgery has more risk of manual mistakes. However, there are also disadvantages that HDR brachytherapy has. For instance, during prostate cancer surgery, the prostate is removed, which means there are fewer possibilities that prostate cancer will occur again. What’s also worth notice is that after a patient undergoes prostate surgery, they can still use HDR brachytherapy. However, once a patient uses HDR brachytherapy, they can no longer have prostate surgeries. Both treatments have major side effects, with HDR brachytherapy mainly causing urinary problems and surgery causing sexual malfunction problems.
From an economic perspective, for patients, the cost of HDR brachytherapy is an issue in choosing this treatment method over traditional surgery treatments. The mean cost of HDR brachytherapy $9,535 (range $8,800–10,380). On top of that, patients usually need active surveillance after the treatment, with an average of $7,298. In contrast, according to the result of the study: The cost of prostate cancer care to society and patients in the United States. The most cost of a prostate surgery averaging $2203 (8,883 performed, average $2,003 each, total $17,694,508) with accompanying anesthesia costing $1262 each.(7,960 performed, total $10,048,653). In comparison, HDR brachytherapy has a total cost of $16833, and prostate surgery has a total cost of $3465, with a difference of $13368. Since prostate cancer mostly happens in people that are retired, with an average diagnosis at 66. According to Statistics Canada, people that were older than 65 years old only have an average income of $6249, which is significantly lower than the average cost of HDR brachytherapy. This makes HDR brachytherapy not a cost-effective treatment as traditional surgery.
To sum up, even though HDR brachytherapy has its limitations, such as unaffordable price and higher recurrence rate after the treatment than surgery, it is still a good option for people who can afford it considering its benefits of being a non-invasive method, no radioactive materials left inside the body and better precision. In the future, a lower cost of HDR brachytherapy will make it a more applicable prostate cancer treatment option for many patients.
