by Oliver Moras
Radiotherapy is a technique which uses high energy electromagnetic waves to break the DNA of cancer cells. This is achieved as high energy waves are likely to cause a double strand break in DNA during mitosis, the process in which cells divide. A double strand break is when both polynucleotide strands are damaged at the same point which results in the damage being harder to repair. An accumulation of double strand breaks results in cell death and the cancer cells would be unable to divide and spread. Healthy cells are also affected and their DNA is damaged by radiotherapy however, normal cells are able to repair better than cancer cells and since cancer cells are dividing cells, a drop in the division efficiency of cancer cells has a larger impact than compared to when healthy cells divide less (as the sole purpose of cancer cell is is rapid division, unlike healthy cells).
The 2 main types of radiation treatment for prostate cancer are beam radiation and seed implantation. Permanent seed brachytherapy, is a minimally invasive procedure which is carried out under a light general anaesthetics. Thin needles are used with ultrasound guidance in order to implant small seeds which contain radioactive material into the cancerous prostate gland. The needle is inserted through the perineum and the areas where seeds are placed are determined using computer software which maps out the procedure beforehand. This procedure is also known as low dose-rate brachytherapy as a lower dose of radiation is released. This reduces the risk of injury to organs such as the bladder, hips and small bowel. It is used to treat low risk, localised prostate cancer since the radiation will not trace beyond the prostate, although it may be suitable for certain intermediate risk cases. This makes it unsuitable for advanced prostate cancer which has spread to other areas of the body but also, it is unsuitable for those with an enlarged prostate and so hormonal therapy may be carried out to shrink the gland beforehand in a combination therapy.
Furthermore, this treatment may further bladder complications for those with Crohn’s disease (an inflammatory bowel disease) or ulcerative colitis (a condition causing the colon and rectum to become inflamed) and it has other possible side effects such as urinary problems and erectile dysfunction. Due to the radioactive materials used, the patient would need to distance themselves from children and pregnant women for the first 2 months after the treatment and in addition to the side effects of making an incision (infection, etc), the side effects of a spinal anaesthetic, etc are present too. The advantages of this treatment are similar to other minimally invasive procedures, where there is a short recovery time (where it is possible to return to normal actives as short as 1 or 2 days after the procedure), the time spent is hospital is short (1-2 days) and in addition, having further treatments is possible in case of resurgence, unlike for many other treatment options.
https://prostatecanceruk.org/prostate-information/treatments/permanent-seed-brachytherapy
Temporary seed brachytherapy also known as High Dose Rate Brachytherapy is type of internal radiotherapy which passes the source of radiation (radioactive seeds) through around 12-16 plastic catheters which enter the body through the perineum with the patient under anesthesia and lead to the prostate, just like with permanent seed brachytherapy. The source is left there for a few minutes, with the exact time determined by a computer, in order to kill the cancer cells before being removed. It is a procedure where many doses are given over the course of a few days in order to thoroughly eliminate the cancer. While it may be less convenient than permanent seed brachytherapy as regular hospital trips are required, by controlling the dosage size delivered to the prostate, the cancer cells are better targeted and the healthy tissue is less affected. Other than these differences, the two types of seed brachytherapy share similar side effects and cure rates.
https://prostatecanceruk.org/prostate-information/treatments/high-dose-rate-brachytherapy
External beam radiation is the other common type of radiation treatment. A machine called a linac aims high energy x-rays at the cancer cells. Three-dimensional conformal radiation therapy, a type of external beam radiation therapy, uses CT scans, PET scans, etc to map out the prostate and then beams of radiation of the same strength are delivered from many directions to treat the cancer and the precise shaping and mapping allows for higher doses of radiation to be used without damaging the healthy tissue. Intensity-modulated radiation therapy, also known as IMRT, is another type of external beam radiation where while beams are similarly aimed at the cancer from several directions after mapping the prostate, smaller beams are used which can have their strength adjusted in order to deliver a higher dose to certain areas of the tumor. This helps to reduce the chance of neighboring healthy tissue getting damaged.
https://prostatecanceruk.org/prostate-information/treatments/external-beam-radiotherapy
When comparing surgical and radiation treatments, in the past, surgical had always been prefered but with the recent development of permanent seed brachytherapy, etc, it is much different. Radioactive seed treatments have the best cure rates out of any treatment option but while it has the highest rates, other treatments are very similar and the difference isn't significant. Nonetheless, it still has higher cure rates and in terms of side effects, the incidence of impotence is much lower compared to surgery and in terms of incontinence, radiation does not increase the chance of developing it at all whereas surgery does. Until recently, the main disadvantage of a radiation approach over surgery was that radiation can cause burns to the rectum wall whereas damage to the rectum due to surgery was much more rare: however, SpaceOAR, a gel spacer, has been developed which when injected between the rectum and prostate, is able to push away the rectum wall, eliminating the risk of burns. On the other hand, the main benefit of surgery over radiation methodologies in the present is that there are more skilled surgeons than radiation therapists. The reason for this, especially in areas such as the Unites States of America without a free healthcare system, is that it is more lucrative to the doctor to perform a robotic-assisted laparoscopic radical prostatectomy than a permanent seed brachytherapy and so many more train in surgical areas.
Source: ‘Prostate Cancer Research Institute’
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