QUALITY ASSURANCE IN BRACHYTHERAPY FOR PROSTATE CANCER
The Prostate
The prostate is a fibromuscular glandular organ that surrounds the prostatic urethra. It is about 1 ¼ inches (3 cm) long and lies between the neck of the bladder above and the urogenital diaphragm below. It is surrounded by a fibrous capsule. Outside the capsule is a fibrous sheath, which is part of the visceral layer of pelvic fascia. The numerous glands of the prostate are embedded in a mixture of smooth muscle and connective tissue, and their ducts open into the prostatic urethra. The prostate is incompletely divided into five lobes (2000).
The function of the prostate is the production of a thin, milky, fluid containing citric acid and acid phospatase. It is added to the seminal fluid at the time of ejaculation. The prostatic secretion is alkaline and helps neutralize the acidity in the vagina.
The prostate gland has a reputation as a health destroyer. Prostate cancer is the most common malignancy (2003), and is the third most prevalent cancer in men (2004). Prostate cancer is a vexing disease because the cure – removal of the prostate – often causes impotence or incontinence. In the past, the main alternative was a combination of hormone therapy to shrink the tumor and radiation treatments to kill cancer cells, which was often less effective and still caused considerable discomfort (1999). As a rule, prostatic cancer is a slow-growing, hidden condition, but it can also be a swift and deadly killer. The treatment of localized prostate cancer is highly controversial, with many treatment options.
Treatment of prostate cancer can include surveillance, “watchful waiting,” radical prostatectomy, androgen hormone ablation, internal or external radiation, surgery, chemotherapy, or a combination of any of these modalities (2002; 2004). Treatment decisions should consider the patient’s age, medical history, tumor stage, and contributing family medical history. The risk/benefit ratio of each treatment option should be considered and discussed thoroughly with the patient and his significant other. The use of radioactive seeds in brachytherapy to provide radiation therapy is one of the three recommended treatment options for localized carcinoma of the prostate (1998). Brachytherapy, or the insertion of radioisotopes directly into the cancer-bearing organ, is gaining acceptance as a treatment, with survival outcomes similar to other treatments. This outpatient procedure has the advantage of patient convenience and cost effectiveness (2003).
Overview of Radiation Therapy
Radiation therapy, or radio therapy, is a branch of radiology used to treat cancer. Radiation is the emission of electromagnetic waves or atomic particles that result from the disintegration of nuclei of unstable or radioactive elements. The treatment of malignant disease of radiation may be referred to as radiation therapy, brachytherapy, or radiotherapy. Ionizing radiation is used for this type of therapy, which involves the use of high-voltage radiation and other radioactive elements to injure or destroy cells. Like surgical resection and photodynamic therapy, radiation therapy is localized therapy that is applicable for a limited number of specific tumors (2004).
A patient is exposed to ionizing radiation in doses to kill a malignancy. Malignant tissues are more sensitive than normal tissues to radiation exposure and can be treated if they have not spread throughout the body and are not surrounded by normal tissue that is especially sensitive to radiation, such as the spinal cord. Sophisticated physical and biological techniques are used for radiation therapy, often accompanied by computer analyses. A radiation therapist develops a treatment plan that permits the absorption of a fatal amount of radiation by all tumor cells but causes relatively minor damage to normal tissue. The usual mode of therapy is an external high-energy beam directed at the tumor site for a few minutes a day for 2 to 6 weeks, depending on the type of malignancy. X-rays, gamma rays, and such isotopes as cobalt-60 and iodine-31 are often used.
To further understand why quality assurance in radiotherapy is vital and why it is important in treatment delivery, a discussion on the effects of radiation on cells will first be provided.
Effects of Radiation on Cells
Cancer cells multiply out of normal body control; they are in a state of active, uncontrolled mitosis (the nuclear division of the cytoplasm and nucleus). Radiation affects the metabolic activity of the cells. Cells in an active state of mitosis are most susceptible. Over time, gamma rays and x-rays cause a cessation of cell growth and a regression of the tumor mass. Cells die and are replaced by fibrous tissue ( 2004).
The sensitivity of a tumor to radiation varies. Some tumors can be destroyed by a small amount of radiation, whereas others require a large amount. The sensitivity of the tumor cells is determined by the sensitivity of the normal cells from which the tumor cells are derived.
The effects of radiation therapy also depend to a large extent on tissue oxygenation. As a tumor grows, the periphery is well oxygenated but the central portion becomes necrotic and poorly oxygenated. The number of cells killed by radiation therapy is directly related to the amount of tissue and oxygen within the tumor. Therefore the hypoxic effect is a factor in determining therapeutic dosage of radiation.
Radiation therefore cannot be limited solely to the area being treated. The danger of injuring normal surrounding tissue is a limiting factor in the dosage and selection of the most appropriate type of radiation therapy. A factor of dosage is the ratio of tumor tissue to the surrounding normal tissue. The penetration of radiation energy is calculated from the rate of decay or disintegration, known as half-life. Half-life is the time required for half of the radioactive material to disintegrate and to lose one half of its activity through decay.
Treatment Modality/Implantation of Radiation Source – Brachytherapy
All radiation sources for implantation are prepared in the desired therapeutic dosages by personnel in the nuclear medicine department. Many types of sources are used to deliver maximum radiation to the primary tumor. It is important to remember that no single type is ideal for every tumor or anatomic site.
Brachytherapy is on type of radiation therapy. The term brachytherapy comes from a Greek term meaning “short-range treatment.” Brachytherapy, or “seeding” the cancer directly with radioactive isotopes embedded in capsules the size of rice grains (1999). Tiny titanium cylinders that contain a radioactive isotope are implanted to deliver a dose of radiation from the inside out that kills cancer cells while sparing healthy tissue. Brachytherapy is performed fro many types of cancers including breast and prostate. It is useful for delivering higher cell-killing doses in shorter periods than conventional radiation treatments. The capsules are placed under ultrasound guidance (2004).
Brachytherapy requires the implantation of radioactive iodine-125 or palladium-103 seeds directly into the prostate. They emit highly localized radiation energy to kill localized cancer cells without excessive harm to nearby healthy cells. Proper placement of these seeds is critical, and a preprocedural map of the prostate gland, using ultrasound or CT, is obtained. A grid is then placed over the perineum and ultrasonic or CT imaging used to deliver seeds to the prostate alone. These seeds remain in the body, but their radioactivity declines over a period of months (2004). It has only been over the past couple of years that seeding has become the treatment of choice for a growing number of doctors and their patients (1999).
Quality Assurance Systems in Place that Govern the Safe Delivery of Brachytherapy
Preparation for brachytherapy typically includes bowel cleansing and administration of prophylactic antibiotics. An oral bowel stimulant such as magnesium citrate may be combined with a cleansing enema to prepare the bowel. The patient should be advised to maintain a clear liquid diet 12 to 24 hours preceding the study as directed. The patient should also be instructed that the procedure is likely to produce rectal pressure or mild discomfort when the ultrasound probe is placed, but pain is not associated with implantation of radioactive seeds ( 2004).
The patient should be educated and informed that the implantation will cause inflammation of the prostate that is likely to provoke bothersome LUTS, including daytime voiding frequency, an increase in nocturia, and difficulty initiating a urinary stream. These manifestations are typically transient and subside as prostatic inflammation diminishes (2004).
In general, the patient and the caregiver should be taught the principles of radiation safety before, during and following brachytherapy. This should be in consultation with the radiation oncologist and based on institutional policies. The cardinal factors of protection from radiation sources, regardless of implantation sites, are distance, time, and shielding. For both personnel and patients, the following principles of radiation safety also apply to handling all types of radioactive materials:
- The intensity of radiation varies inversely with the square of the distance from it. Personnel should stay as far from the source as feasible.
- Radiation sources such as needles, seeds, capsules, and suspensions are prepared by the personnel in the nuclear medicine department. Personnel prepare these sources behind a lead screen, and their hands are protected by lead-lined gloves, if possible, or special forceps during handling.
- Radiation sources are transported in a long-handled lead carrier so they are as close to the floor as and as far away from the body of the transporter as possible. The lead carrier should be stored away from personnel and patient traffic areas while it is in the operating room suite.
- When radiation sources are delivered to the operating room, each needle, seed, or capsule as are the ones placed in the prostate, is counted by the surgeon with the radiation therapist. This number is recorded.
- Glutaraldehyde solution is poured into the lead carrier to completely submerge the radiation sources. When ready to use, the radiation source is transported in the lead carrier into the operating room. The needles, seeds, or capsules are removed from the lead container with sterile, long-handled instruments and are rinsed thoroughly with sterile water.
- All radiation sources are handled with special long, ring-handled forceps from behind a lead protection shield. Radiation sources should never be touched with bare hands or gloves. Radiation sources are never handled with a crushing forceps because the seal of hollow containers can be broken. A groove-tipped forceps that is designed for this purpose is used.
- Radiation sources are handled as quickly as possible to limit the time that personnel are exposed to radiation.
- All radiation sources are accounted for before and after use, and any loss is immediately reported. Nothing should be removed from the room. To locate a lost radiation source, a radiation therapist or nuclear medicine department technician is called to bring a Geiger counter. A Geiger counter has a radiation-sensitive gauge with an indicator that moves and a sound that increases when near radioactive substances.
- A radiation documentation sheet is completed and put in the patient’s chart. The surgeon fills in the amount and exact time of insertion and the time the source is to be removed. Each health care professional who cares for the patient on the unit signs this sheet just before going off duty, thereby passing responsibility for checking the patient and radiation source to the health care professional who relieves.
- The patient’s bed and door to the room are conspicuously labeled with a radiation-in-use card or symbol.
- The radiation source is removed by the surgeon at the exact time indicated so the patient will not be overexposed.
- Radiation is neither seen nor felt. Therefore the rules are carefully observed. Exposure is monitored and minimized.
Effects of Radiation Therapy on the Patient
The patient may be undergoing several treatment modalities and may experience the specific tissue and systemic effects of each. Health care professionals caring for the patient should understand how radiation affects the patient and how it affects the attainment of desired outcomes. The plan of care therefore should include consideration for the potential side effects of radiation therapy.
In one study, it was demonstrated that when brachytherapy is evaluated 6 months after treatment, bowel, bladder, and sexual functioning are affected. The impact of brachytherapy on quality of life of the patient appears to be tolerable. Although each of the participants in the study made several statements related to their post treatment physical functioning, the negative statements were qualified by minimizing the problem, or stating the possibility that other factors may be influencing the difficulty (2003).
Acute urinary retention is also one of the most common complications following prostate brachytherapy, occurring in 1% to 22% of patients in various studies ( 2003). However, one study also demonstrated that reducing urethral dosage in patients undergoing brachytherapy for localized prostate cancer decreases the rate of post-implant urinary retention (2003)
Summary and Conclusion
The process of radiation therapy involves the use of rays that could be harmful to the body. Quality assurance is therefore vitally important in all aspects of radiation therapy to ensure that the treatments delivered are safe and effective. Brachytherapy for treatment of prostate cancer has been widely used and although found to have some side effects in the long run, are able to treat cancer patients well. Although some studies have shown negative effects as a result of brachytherapy, it is tolerable and is not without a remedy. A safe and effective brachytherapy could do wonders for the patient and its side effects are just minima compared to what harm could have been done if brachytherapy was not performed. The principles of radiation safety also apply to handling brachytherapy to ensure a safe and effective treatment.
Credit:ivythesis.typepad.com
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