St. John Providence Health System offers the area’s most comprehensive radiation therapy services. Our physicians are actively involved in clinical trials of new radiation treatments – often giving patients access to the newest, most promising cancer treatments before they are widely available.
What is Radiation Therapy?
Radiation therapy is the treatment of cancer using penetrating beams of high-energy waves called radiation. The radiation used for cancer treatment comes from special machines or from radioactive substances. In small doses over a period of several weeks, the diseased area is exposed to highly focused energy waves that disrupt the ability of the cancer cells to grow and multiply. Treatment is generally painless, though some patients experience side effects.
Types of Radiation Therapy
At Providence Cancer Institute, a variety of advanced radiation therapy options are available. Our expert radiation oncologists will work with you and your physician to determine the most effective and most appropriate treatment option.
Advanced Treatments for Different Types of Cancer
One of the most advanced forms of cancer treatment, Intensity Modulated Radiation Therapy (IMRT) utilizes computer-controlled x-ray accelerators to deliver precise radiation doses to a malignant tumor or specific areas of a tumor. The radiation dose is designed to conform to the shape of the tumor – focusing a high dose of radiation on the tumor while minimizing exposure to surrounding tissues.
With IMRT, higher and more effective radiation doses can safely be delivered to tumors with fewer side effects compared with conventional radiotherapy techniques.
High dose rate brachytherapy is termed temporary because the radioactive source does not remain within the body after the treatment, in contrast to permanent implants. A special applicator is used which is specific for each cancer. The applicator is placed within the tumor and the high dose rate machine moves a radioactive source through the tube to deliver dose from within the tumor. After a specified period of time within the tube the source retracts into the machine. The applicator may remain in place for 1-2 weeks, but patients are rarely aware of its presence due to custom fitting and placement. Often 2 to 3 separate treatments are done days apart. High dose rate treatment is most commonly used for gynecological cancers such as endometrial, vaginal, or cervix carcinoma. It is often combined with external beam radiation.
Tiny radioactive seeds are implanted into the tumor. Radiation from the seeds then kills nearby cancer cells. One advantage of this type of treatment is that it is completed within one day, but the radiation continues to kill cancer cells for weeks or months. Permanent seed implants are commonly used for prostate cancer, and are commonly combined with external beam treatment (see Specialized Prostate Cancer Treatments below)
Using an external stereotactic device and advanced imaging technologies, radioactive implants can be precisely placed into the brain to destroy cancer cells in the brain. This technique is useful in recurrent adult brain tumors and does not require craniotomy (surgical opening of the skull). The source is placed within a tiny catheter and passed through a small hole in the skull to the center of the tumor.
Specialized Prostate Cancer Treatments
The vessel-sparing radiation technique was pioneered by Dr. McLaughlin at Providence Hospital and reported in the January 2005 issue of the International Journal of Radiation Oncology, Biology, and Physics. This technique is currently only available at Providence Hospital.
In addition to the desire for the highest cure rate possible, a critical concern for men treated for prostate cancer is quality of life following treatment. Several critical functions pass near or through the prostate and if dose is limited to these structures, long-term effects on these critical functions may be minimal. Among the critical quality of life concerns sexual function after prostate cancer therapy ranks very high for sexually active men. Dose to critical erectile tissues can be limited if the tissues are visualized. In a special protocol, prostate cancer patients who want to preserve erectile function can undergo special scans to define the blood vessels responsible for erections. When dose is limited to these critical structures, the risk of erectile dysfunction is very low. In the process of obtaining images of these erectile tissues, extremely clear images of the urinary sphincters and rectum are obtained. As a result, these structures can be avoided, lowering the risk of urinary or rectal problems following treatment.
Vessel sparing radiation is similar to nerve-sparing prostatectomy. Over a decade ago it was discovered that nerves responsible for erections could be spared during prostate removal for cancer. Interestingly, the nerves are not affected by radiation, and the mechanism of erection problems after radiation is vessel related rather than nerve related. Both procedures – nerve-sparing surgery and vessel-sparing radiation – demonstrate that physicians treating cancer want to accomplish two things: cure the cancer and preserve quality of life.
One of the most effective treatments for prostate cancer is the combination of seed implantation with external radiation. Radioactive seeds implants (a half-day, outpatient procedure) provide a very high dose of radiation to the prostate cancer because the seeds are actually placed within the prostate and within the cancer. The dose to surrounding tissues is extremely low. Radiation beam treatment can deliver a cloud of radiation around the prostate to destroy any cancer cells which may have escaped the prostate.
In a unique protocol only available at Providence Hospital, the beam radiation is delivered after the implant and the dose delivered by the beam is adjusted to take the implant dose into consideration. This requires an elaborate computer program pioneered at the University of Michigan to precisely calculate dose from the implant and combine it with dose from the beam to achieve the ultimate goal of treatment – delivering a very high dose to the tumor while limiting the dose to normal tissues. The prior strategy – beam followed by implantation, did not allow correction and adjustment of implant dose irregularities.
Seed implants for prostate cancer are a proven effective treatment for prostate cancer. Seed implant alone is appropriate for some prostate cancers or may be combined with beam radiation (see IMRT Beam Radiation Combined With Permanent Seed Implant). The most critical predictor of cure following implants is implant quality. This refers to the degree to which the seeds remain in proper position and deliver the desired dose to the prostate. This must be checked after the seeds are placed and after the postoperative swelling changes have resolved. Unfortunately, the seeds interfere with the CT scan and it is difficult to define the prostate due to the blurring effect of seeds.
One solution to the problem is combining CT scans and MRI scans. Although the prostate is blurred on CT scans after seed implant, it is clearly defined on MRI. On the other hand the seeds are difficult to see on MRI. Thus the combination of the CT scan and the MRI provide a clear picture, allowing a true and accurate check of the implant quality. If seeds have moved out of position and the prostate is not well covered by dose, corrective seeds can be placed in a brief 15-minute correction procedure (rarely required).
Combining MRI and CT scans is a complex process, and accurate combining of scans in an efficient fashion has been an important research effort at Providence Hospital. Due to the efficiency and accuracy achieved, all patients undergoing prostate seed implant have combined MRI and CT check. In addition this same technology to combine MRI and CT scans is used in patients treated with external beam therapy to better define critical adjacent structures (see Vessel-Sparing Radiation).