In this era of minimally invasive medicine, one of the options for the treatment of prostate cancer is the use of radiation therapy. This form of therapy allows treatment of the prostate cancer in a non-invasive way. There are various options, including IMRT (intensity modulated radiation therapy), IGRT (image guided radiation therapy, brachytherapy (regular and high dose), proton beam and cyberknife therapy. The properties of the radiation source that is utilized determines the effects on the tumor as well as the side-effects that may be associated with the treatment.
Proton beam therapy, although approved by the FDA in 1988, is offered at very few locations in the US. A particle accelerator is used, and the charged protons, which are relatively large positively charged particles,are released. This damages the DNA of the cell, resulting in cellular death or altered cellular division. This technology involves a proton beam that enters the patient at a low dose and at a precise depth. A large burst of energy is delivered to the targeted cells. After the release of the proton beam no further energy is emitted. Tumors that are deeper within the body are treated with higher energy levels.The finite period of energy release is supposed to limit the damage to the surrounding healthy tissue, and therefore result in fewer short and long-term side effects. Reportedly there is a decreased risk of the development of secondary malignancies as well.
Traditional radiation therapy involves the use of photon therapy which has different properties than the proton beam. X-ray therapy(which includes IMBRT, Brachytherapy, Cyberknife) utilizes electromagnetic waves which do not have mass or charge. The energy enters the body at a relatively higher dose that dissipates over the depth of tissue which it has to penetrate. Proton therapy differs in that it penetrates the tissue and releases its maximum dose at a precise depth.
However, availabilty of this treatment is still an issue. A recent study in the Archives of Internal Medicine has identified that the likelihood of patients undergoing treatment with proton beam therapy is related to the distance that they live from one of these facilities; "if you build it, they will come."
Cyberknife therapy is another minimally invasive alternative for the treatment of prostate cancer. Although it sounds like it is a surgical technique, it involves the use of a compact linear accelerator that is mounted on a robotic arm that delivers high dose radiation to tumors with great accuracy. It utilizes image guidance software that allows constant feedback during the treatment, allowing ongoing adjustment during the treatment. The robotic arm stops at positions that are predetermined by computer software corresponding to the location of the prostate. The more than 1,000 possible treatment positions minimize radiation to adjacent structures.
The convergence of many fine beams of radiation results in a high dose of radiation to the tumor and avoiding nearby normal tissue. This technique usually involves five days of therapy and does not require inpatient hospitalization. It was originally approved by the FDA in 2001 for the treatment of solid organ tumors and more recently has been used for the treatment of prostate cancer. Long-term cure rates with the use of this technology have not yet been determined. Due to the nature of the treatment, relapse rates at the edge of the treated target remains a concern. It is presently being offered as either a primary treatment or as a boost treatment after standard external beam radiation therapy.
When performing IGRT, CT image guidance provides detailed information about the target, thus allowing the use of a smaller radiation field and less radiation to surrounding normal tissue, similar to the cyberknife. During the bladder's "filling phase," there is some minor movement of the prostate, and this technology helps account for the prostatic motion. This technique uses 3-D imaging techniques to localize the tumor, thus delivering a radiation treatment with a higher dose of radiation. The ability to carefully target tissue allows minimal exposure to organs that surround the prostate such as the rectum and bladder. IGRT is often used as a companion to IMRT and can be used to guide the IMRT to the target.
IMRT is a radiation technique which focuses very small beams of radiation at a targeted tumor from many different angles. This type of technology allows for a direct treatment of the tumor. A collimator is used to adjust the shape and size of the radiation beam, allowing for the careful focusing of the beam. The careful focusing and shaping of the treatment beam leads to a precise treatment with little tissue damage to surrounding tissues. However, limitations to this form of treatment exist, but these limitations are overcome when coupling this with IGRT.
Brachytherapy involves the placement of radioactive seeds of either Iodine-125 or Palladium-103 into the prostate. The radioactive properties of these seeds vary with Iodine-125 having a radioactive half-life of 60 days and Palladium-103 having a 17 day half-life. The properties of the tumor will help the radiation therapist determine which type of seed to use. The seeds are placed under anesthesia through the perineum directly into the prostate in an out-patient procedure. High-dose brachytherapy involves the placement of thin catheters containing radioactive sources into the prostate. The catheters are left in place for a period of time depending on the treatment protocol. The high dose treatment is not utilized very frequently as there are other techniques that can deliver a similar dose in a non-invasive manner.
Once diagnosed with prostate cancer, patients often are frenzied. They think that since they have cancer, they immediately need the cancer removed. With prostate cancer; this is not necessarily true. A careful consideration of non-invasive, minimally-invasive, and invasive therapies should be considered. A consultation with a radiation therapist should be considered, and perhaps after hearing all the options, one of these therapies may best be suited for you.
Published On: March 01, 2012