Evolution of Radiation Therapy for Prostate Cancer
Hugh Hampton Young, M.D., performed the first radical prostatectomy—the surgery to remove a cancerous prostate—at Johns Hopkins Hospital more than a century ago in 1904. Although hailed as a success, the operation was difficult to perform because doctors had to operate in a virtual sea of blood, which made it extremely hard to see what they were doing.
In addition, the surgery came with two devastating side effects. One in four men experienced severe problems with urinary control, and every man lost the ability to have an erection.
The result was that both doctor and patient felt that the side effects from the surgery were almost worse than having prostate cancer. In the ensuing decades, not many men opted for prostate surgery.
The beginnings of radiation therapy
Young was not daunted in his quest in finding a prostate cancer cure. In the early 1900s, while perfecting surgical techniques, he also began experimenting with placing radioactive radium pellets into the prostate as a treatment for prostate cancer. Unfortunately, radiation injury to patients and physicians limited the application of those initial attempts.
Still, he saw the real potential of the therapy. He noted, “In radium we undoubtedly have a therapeutic agent of great value in urology and with improved apparatus many brilliant results should be obtainable.”
Fast forward to the 1990s, and Young’s prophecy came to be. Thanks to a much better understanding of radiation and improved technology that saw the advent of three-dimensional imaging using computed tomography (CT) scanners, combined with linear accelerators that could produce a high-energy photon beam, it became possible to deliver high dosages of radiation more precisely to the prostate deep within the pelvis.
Computer programs were developed to plan radiation dosages based on a three-dimensional image of the prostate. Now referred to as three-dimensional conformal radiotherapy, or 3DCRT, it allowed the use of precisely directed high-radiation dosages and at the same time reduced the injury to nearby healthy rectal and bladder tissue from the radiation.
Many more choices exist
The good news today for men with localized prostate cancer is that there are now many ways to successfully treat the cancer. And the bad news is that there are now many ways to successfully treat prostate cancer. Deciding what therapy to choose is often very difficult for most men.
There is no scientific evidence that any one treatment for localized prostate cancer—whether radiation or surgery—will result in a better cancer-free outcome than another. This means that a man and his family will have to play a much larger role in decision making. The same men who are candidates for surgical treatment of stage T1 and T2 cancers are also eligible for radiation therapy.
Radiation therapy has some advantages, including no hospital stay or lengthy at-home rehabilitation. External radiation treatments are administered daily but are brief, and men can lead relatively normal lives around their treatment times. But there are some side effects, including fatigue, bladder irritation, and loose, frequent stools, though they are generally mild and can be eased with medication and changes in diet.
A more precise therapy
Radiation therapy for prostate cancer continues to evolve. Radiation oncologists and medical physicists have made a number of improvements in external beam radiation therapy in an attempt to increase cure rates and reduce the risk of complications.
These improvements include three-dimensional conformal radiation therapy (3DCRT), intensity modulated radiation therapy (IMRT), and image-guided radiation therapy (IGRT).
We are now in the era of IGRT, since the patient can be moved to realign his anatomy, ensuring that the radiation is precisely focused on the target at every treatment session. Treatment can also be adapted if the patient loses weight, for example, which results in changes in anatomy.
IGRT uses daily computed tomography (CT) scanning to create three-dimensional images that pinpoint the exact size and location of the prostate just before treatment. This information is then transmitted to a computer, allowing doctors to compare the current image with earlier images taken on previous treatment days.
During IGRT, doctors continually compare those images to see if the treatment area needs to be adjusted. Radiation specialists use IGRT to deliver more radiation to the tumor, ultimately leading to higher cure rates and more tolerable side effects.
How radiation kills cancer cells
Normal cells in the body divide and replace themselves in an orderly process, keeping you healthy and repairing structures as needed. However, cancer develops when the cells lose the ability to control their own growth. The cancer cells keep dividing, eventually forming clumps of tissue called tumors, or sometimes infiltrating throughout normal tissue and spreading beyond the organ where they originated—a process called metastasis.
DNA is the genetic information inside the cell necessary for life. Radiation therapy kills cells by damaging their DNA—either directly or by creating the charged particles called free radicals that can cause DNA damage.
When the injured DNA cannot be repaired, cells die. But radiation kills normal cells as well as cancerous cells, and so treatment must be directed precisely at the tumor. Since the prostate is a dispensable organ, radiation can be given at doses that will destroy all prostate tissue, normal and cancerous.
However, radiation dosages are limited by the damage caused to surrounding structures. So the radiation oncologist must achieve a delicate balance between delivering enough radiation that it destroys all the cancer but without causing collateral damage to neighbors such as the bladder and rectum, which can bring about serious side effects—some of them permanent if great care is not taken.
These can include urinary and bowel frequency and urgency, pain with urination and bowel movements, and bleeding. And, just as with radical prostatectomy, there is the potential for the radiation to damage the erectogenic nerves and vessels, resulting in erectile dysfunction.
Phuoc T. Tran, M.D., Ph.D., is associate professor of radiation oncology and molecular radiation sciences, oncology and urology, at the Johns Hopkins Sidney Kimmel Comprehensive Cancer Center. A Johns Hopkins faculty member since 2009, he treats patients with cancers of the genitourinary system and uses stereotactic radiation techniques (such as SRS and SBRT/SABR) for the treatment of patients with oligometastatic disease. His research focuses on the improvement of clinical radiotherapy for the treatment of prostate, adrenal, bladder, penile, testicular, and urethral cancer as well as patients with oligometastatic disease.