Brachytherapy
Brachytherapy is a form of radiation therapy where a sealed radiation source is placed inside or next to the area requiring treatment. The word "brachytherapy" comes from the Greek word, meaning "short-distance" or "short". Brachytherapy is commonly used as an effective treatment for cervical, prostate, breast, esophageal and skin cancer and can also be used to treat tumours in many other body sites. Treatment results have demonstrated that the cancer-cure rates of brachytherapy are either comparable to surgery and external beam radiotherapy or are improved when used in combination with these techniques. Brachytherapy can be used alone such as in early prostate cancer or in combination with other therapies such as surgery, EBRT and chemotherapy such as in advanced cervical cancer
Brachytherapy contrasts with unsealed source radiotherapy, in which a therapeutic radionuclide is injected into the body to chemically localize to the tissue requiring destruction. It also contrasts to External Beam Radiation Therapy, in which high-energy x-rays are directed at the tumour from outside the body. Brachytherapy instead involves the precise placement of short-range radiation-sources directly at the site of the cancerous tumour. These are enclosed in a protective capsule or wire, which allows the ionizing radiation to escape to treat and kill surrounding tissue but prevents the charge of radioisotope from moving or dissolving in body fluids. The capsule may be removed later, or it may be allowed to remain in place.
A feature of brachytherapy is that the irradiation affects only a very localized area around the radiation sources. Exposure to radiation of healthy tissues farther away from the sources is therefore reduced. In addition, if the patient moves or if there is any movement of the tumour within the body during treatment, the radiation sources retain their correct position in relation to the tumour. These characteristics of brachytherapy provide advantages over EBRT – the tumour can be treated with very high doses of localised radiation whilst reducing the probability of unnecessary damage to surrounding healthy tissues.
A course of brachytherapy can be completed in less time than other radiotherapy techniques. This can help reduce the chance for surviving cancer-cells to divide and grow in the intervals between each radiotherapy dose. Patients typically have to make fewer visits to the radiotherapy clinic compared with EBRT, and may receive the treatment as outpatients. This makes treatment accessible and convenient for many patients. These features of brachytherapy mean that most patients are able to tolerate the brachytherapy procedure very well.
The global market for brachytherapy reached US$680 million in 2013, of which the high-dose rate and LDR segments accounted for 70%. Microspheres and electronic brachytherapy comprised the remaining 30%. One analysis predicts that the brachytherapy market may reach over US$2.4 billion in 2030, growing by 8% annually, mainly driven by the microspheres market as well as electronic brachytherapy, which is gaining significant interest worldwide as a user-friendly technology.
Medical uses
Brachytherapy is commonly used to treat cancers of the cervix, prostate, breast, and skin.Brachytherapy can also be used in the treatment of tumours of the brain, eye, head and neck region, respiratory tract, digestive tract, urinary tract, female reproductive tract, and soft tissues.
As the radiation sources can be precisely positioned at the tumour treatment site, brachytherapy enables a high dose of radiation to be applied to a small area. Furthermore, because the radiation sources are placed in or next to the target tumour, the sources maintain their position in relation to the tumour when the patient moves or if there is any movement of the tumour within the body. Therefore, the radiation sources remain accurately targeted. This enables clinicians to achieve a high level of dose conformity – i.e. ensuring the whole of the tumour receives an optimal level of radiation. It also reduces the risk of damage to healthy tissue, organs or structures around the tumour, thus enhancing the chance of cure and preservation of organ function.
The use of HDR brachytherapy enables overall treatment times to be reduced compared with EBRT.
Patients receiving brachytherapy generally have to make fewer visits for radiotherapy compared with EBRT, and overall radiotherapy treatment plans can be completed in less time.
Many brachytherapy procedures are performed on an outpatient basis. This convenience may be particularly relevant for patients who have to work, older patients, or patients who live some distance from treatment centres, to ensure that they have access to radiotherapy treatment and adhere to treatment plans. Shorter treatment times and outpatient procedures can also help improve the efficiency of radiotherapy clinics.
Brachytherapy can be used with the aim of curing the cancer in cases of small or locally advanced tumours, provided the cancer has not metastasized. In appropriately selected cases, brachytherapy for primary tumours often represents a comparable approach to surgery, achieving the same probability of cure and with similar side effects.
However, in locally advanced tumours, surgery may not routinely provide the best chance of cure and is often not technically feasible to perform. In these cases radiotherapy, including brachytherapy, offers the only chance of cure.
In more advanced disease stages, brachytherapy can be used as palliative treatment for symptom relief from pain and bleeding.
In cases where the tumour is not easily accessible or is too large to ensure an optimal distribution of irradiation to the treatment area, brachytherapy can be combined with other treatments, such as EBRT and/or surgery. Combination therapy of brachytherapy exclusively with chemotherapy is rare.
Cervical cancer
Brachytherapy is commonly used in the treatment of early or locally confined cervical cancer and is a standard of care in many countries.Cervical cancer can be treated with either LDR, PDR or HDR brachytherapy.
Used in combination with EBRT, brachytherapy can provide better outcomes than EBRT alone.
The precision of brachytherapy enables a high dose of targeted radiation to be delivered to the cervix, while minimising radiation exposure to adjacent tissues and organs.
The chances of staying free of disease and of staying alive are similar for LDR, PDR and HDR treatments.
However, a key advantage of HDR treatment is that each dose can be delivered on an outpatient basis with a short administration time providing greater convenience for many patients.
Research shows locally advanced carcinoma of the cervix must be treated with a combination of external beam radiotherapy and intracavity brachytherapy.
Prostate cancer
Brachytherapy to treat prostate cancer can be given either as permanent LDR seed implantation or as temporary HDR brachytherapy.Permanent seed implantation is suitable for patients with a localised tumour and good prognosis and has been shown to be a highly effective treatment to prevent the cancer from returning. The survival rate is similar to that found with EBRT or surgery, but with fewer side effects such as impotence and incontinence. The procedure can be completed quickly and patients are usually able to go home on the same day of treatment and return to normal activities after one to two days.
Permanent seed implantation is often a less invasive treatment option compared to the surgical removal of the prostate.
Temporary HDR brachytherapy is a newer approach to treating prostate cancer, but is currently less common than seed implantation. It is predominantly used to provide an extra dose in addition to EBRT as it offers an alternative method to deliver a high dose of radiation therapy that conforms to the shape of the tumour within the prostate, while sparing radiation exposure to surrounding tissues.
HDR brachytherapy as a boost for prostate cancer also means that the EBRT course can be shorter than when EBRT is used alone.
Breast cancer
Radiation therapy is standard of care for women who have undergone lumpectomy or mastectomy surgery, and is an integral component of breast-conserving therapy.Brachytherapy can be used after surgery, before chemotherapy or palliatively in the case of advanced disease. Brachytherapy to treat breast cancer is usually performed with HDR temporary brachytherapy. Post surgery, breast brachytherapy can be used as a "boost" following whole breast irradiation using EBRT.
More recently, brachytherapy alone is used to deliver APBI, involving delivery of radiation to only the immediate region surrounding the original tumour.
The main benefit of breast brachytherapy compared to whole breast irradiation is that a high dose of radiation can be precisely applied to the tumour while sparing radiation to healthy breast tissues and underlying structures such as the ribs and lungs. APBI can typically be completed over the course of a week. The option of brachytherapy may be particularly important in ensuring that working women, the elderly or women without easy access to a treatment centre, are able to benefit from breast-conserving therapy due to the short treatment course compared with WBI.
There are five methods that can be used to deliver breast brachytherapy: Interstitial breast brachytherapy, Intracavitary breast brachytherapy, Intraoperative radiation therapy, Permanent Breast Seed Implantation and non-invasive breast brachytherapy using mammography for target localization and an HDR source.