Radiation Therapy for Testicular Cancer
The objective of radiation therapy is to kill testicular cancer cells for a maximum probability of cure with a minimum of side effects. The role of radiation in the treatment for testicular cancer depends predominantly on the histologic classification and the stage of the cancer. Radiation is generally given in the form of high-energy beams that deposit the radiation dose in the body where the risk of cancer cells is greatest. Radiation therapy, unlike chemotherapy, is considered a local treatment. Cancer cells can only be killed where the actual radiation is delivered to the body. If cancer exists outside of the radiation field, the cancer cells are not destroyed by the radiation. Therefore, radiation therapy is typically used as primary treatment for early stage cancers confined to a single location (field) in the body.
Histology. The great majority (95%) of testicular cancers derive from germinal elements (i.e. involved in reproduction) and are referred to as germ cell cancers. Testicular cancers, in general, are classified as either seminoma or non-seminomatous germ cell cancers. Seminomas are the most common type of germ cell cancers, accounting for about 40%. Examples of non-seminomatous germ cell cancers include embryonal cell carcinoma, teratocarcinoma, teratoma, and choriocarcinoma. The non-seminomatous germ cell cancers frequently appear in mixed combinations, i.e. more than one type present. Radiation therapy is a major component of the overall treatment approach for seminomas because the cancer cells can be easily destroyed with radiation therapy. Radiation therapy is used less frequently as treatment of non-seminomatous germ cell cancers because these cancers are more difficult to kill with radiation.
Stage I Seminoma is a cancer confined to the testes. The initial diagnosis and treatment is established with orchiectomy (surgical removal of the testes). Following surgery, the treatment of choice traditionally has been radiation therapy to the pelvis and para-aortic lymph node regions where cancer cells can spread. Cure rates in excess of 95% are routinely achieved with radiation therapy following surgery.
The development of improved staging techniques, including CT scanning, and the realization that patients who experience cancer recurrences still have an excellent chance of being cured with additional chemotherapy following surgical treatment alone for stage I seminoma has raised the question of whether all patients should be treated with radiation therapy as initial treatment. Seventy-five to eighty-five percent of patients who present with stage I cancer are cured with surgery alone and may not need radiation therapy. Fifteen to twenty-five percent of patients will relapse without radiation therapy. While the side effects of modern radiation therapy are mild, and the probability of complications low, as many as 75% of patients would be treated with radiation therapy unnecessarily.
Patients may choose to receive treatment with surgery alone followed by frequent visits to the doctor for the purpose of detecting early cancer recurrence. Radiation or chemotherapy is administered at the time of recurrence with similar success.
If the decision is made to not receive radiation therapy, patients need to be frequently evaluated by their doctor to ensure early detection of cancer recurrence. A typical schedule for patients who choose to be observed rather than to immediately undergo radiation therapy would be monthly physical examinations, blood work and chest and abdominal X-rays, with CT scans every two to three months. The frequency of these tests are scheduled progressively further apart in subsequent years. This approach of intense observation is often referred to as surveillance and is necessary for a minimum of 5 years and possibly 10 years after orchiectomy.
Because of the many considerations involved, the decision whether or not to undergo radiation therapy may not be an easy one to make. A compromise approach that is receiving increasing acceptance is to undergo radiation therapy to the para-aortic region, omitting treatment of the pelvis. In stage I seminoma, the incidence of pelvic lymph node involvement with cancer is thought to be less than 2%. Avoiding radiation to the pelvic region greatly diminishes the probability of radiation side effects, including infertility and gastrointestinal discomfort. Treatment of areas above the diaphragm (i.e. “mediastinal irradiation”) is no longer practiced for stage I or II seminoma.
Stage II Seminoma is cancer that has spread to regional lymph nodes. Patients are usually divided into 2 groups, those with “minimal” or “bulky” (greater than 5 cm) lymph nodes. Therefore, a patient with cancer in the para-aortic lymph nodes less than or equal to 5 cm in size would be classified as having a stage IIA cancer. Patients with cancer in the lymph nodes measuring more than 5 cm have stage IIB cancer.
Patients with stage IIA disease are treated with radiation therapy techniques similar to stage I, with the exception that a higher dose of radiation is often used. Treatment results are excellent, with most medical centers reporting 5-year survival in excess of 95%. The treatment of stage IIB seminoma is more complicated. The cure rate with radiation therapy alone is lower, and a significant proportion of the patients will subsequently develop recurrent cancer elsewhere in the body. With the demonstration that Platinol®-based chemotherapy regimens are highly effective treatment for seminoma, patients with stage IIB cancer are increasingly offered treatment with chemotherapy instead of radiation. Radiation therapy is reserved for the 10-15% of patients who then develop evidence of cancer recurrence after chemotherapy.
Stage III Seminoma is cancer that has spread beyond the para-aortic lymph nodes. Patients are typically treated with a Platinol®-based chemotherapy treatment regimen. Radiation therapy is usually reserved for those patients who recur or do not respond to chemotherapy.
Non-Seminomatous Testicular Cancers. As described elsewhere, the treatment for non-seminomatous germ cell cancers after orchiectomy depends on the stage of the cancer. Radiation therapy is not used routinely, but is reserved for those patients who have failed chemotherapy or who have metastases outside the lymph node regions. Possible sites of distant metastases in testicular cancers include the lungs, brain, liver, bones and other areas.
Delivery of Radiation Therapy for Testicular Cancers
Modern radiation therapy for testicular cancers is given via machines called linear accelerators, which produce high-energy external radiation beams that penetrate the tissues and deliver the radiation dose deep into the areas where the cancer resides. These modern machines and other state-of-the-art techniques have enabled radiation oncologists to significantly reduce side effects while improving the ability to deliver a curative radiation dose to cancer-containing areas and minimizing the radiation dose to normal tissue. For example, with modern radiation therapy, skin burns almost never occur, unless the skin is being deliberately targeted or because of unusual patient anatomy.
After an initial consultation with a radiation oncologist, the next session is usually a planning session which is called a simulation. During this session, the radiation treatment fields and most of the treatment planning are determined. Of all the visits to the radiation oncology facility, the simulation session may actually take the most time. During simulation, patients lie on a table somewhat similar to that used for a CT scan. The table can be raised and lowered and rotated around a central axis. The “simulator” machine is a machine whose dimensions and movements closely match that of an actual linear accelerator. Rather than delivering radiation treatment, the simulator lets the radiation oncologist and technologists see the area to be treated. The simulation is usually guided by fluoroscopy, so that a patient’s internal anatomy can be observed (mainly the skeleton, but if contrast is given, the kidneys, bowels, bladder or esophagus can be visualized as well). The room is periodically darkened while the treatment fields are being set and temporary marks may be made on the patient’s skin with magic markers. The radiation oncologist is aided by one or more radiation technologists and often a dosimetrist, who performs calculations necessary in the treatment planning. The simulation may last anywhere from fifteen minutes to an hour or more, depending on the complexity of what is being planned. Once the aspects of the treatment fields are satisfactorily set, x-rays representing the treatment fields are taken. In most centers, the patient is given multiple “tattoos,” which mark the treatment fields, and replace the marks previously made with magic markers. These tattoos are not elaborate and consist of no more than pinpricks followed by ink, appearing like a small freckle. Tattoos enable the radiation technologists to set up the treatment fields each day with precision, while allowing the patient to wash and bathe without worrying about obscuring the treatment fields.
Radiation treatment is usually given in another room separate from the simulation room. The treatment plans and treatment fields resulting from the simulation session are transferred over to the treatment room, which contains a linear accelerator focused on a patient table similar to the one in the simulation room. The treatment plan is verified and treatment started only after the radiation oncologist and technologists have rechecked the treatment field and calculations, and are thoroughly satisfied with the “setup”.
A typical course of radiation for early stage seminoma would entail daily radiation treatments, Monday through Friday, for 3 to 5 weeks. The actual treatment with radiation generally lasts no more than a few minutes, during which time the patient is unlikely to feel any discomfort. Anesthesia is not needed for radiation treatments and patients generally have few restrictions on activities during radiation therapy. Many patients continue to work during the weeks of treatment. Patients are encouraged, however, to carefully gauge how they feel and not overexert themselves.
Side Effects and Complications
The vast majority of patients are able to complete radiation therapy for testicular cancer without significant difficulty. Side effects and potential complications of radiation therapy are infrequent and when they do occur are typically limited to the areas that are receiving treatment with radiation. The chance of a patient experiencing side effects, however, is highly variable. A dose that causes some discomfort in one patient may cause no side effects in other patients. If side effects occur, the patient should inform the technologists and radiation oncologist because treatment is almost always available and effective.
Radiation therapy to the abdominal/pelvic area may cause diarrhea, abdominal cramping or increased frequency of bowel movements or urination. These symptoms are usually temporary and resolve once the radiation is completed. Occasionally abdominal cramping may be accompanied by nausea. Pelvic radiation therapy in men in the past has also been associated with decreased sperm counts, resulting in infertility. Special blocks and shields are used to minimize the scattered radiation and reduce the effect on sperm counts.
Blood counts can be affected by radiation therapy. In particular, the white blood cell and platelet counts may be decreased. This is dependent on how much bone marrow is in the treatment field and whether the patient has previously received or is receiving chemotherapy. These changes in cell counts are usually insignificant and resolve once the radiation is completed. However, many radiation therapy institutions make it a policy to check the blood counts at least once during the radiation treatments. It is not unusual for some patients to note changes in sleep or rest patterns during the time they are receiving radiation therapy and some patients will describe a sense of tiredness and fatigue.
Late complications are infrequent following radiation treatment of testicular cancer. Potential complications do include bowel obstruction, ulcers or second cancers caused by the radiation. The probabilities of these late complications are also affected by previous extensive abdominal or pelvic surgery, radiation therapy and/or concurrent chemotherapy.
Radiation for Chemotherapy-Resistant Cancers, Palliation, or Distant Metastases
As mentioned previously, chemotherapy is the mainstay of treatment of non-seminomatous testicular cancers. Occasionally, a cancer may stop responding to chemotherapy, especially large cancers. In these instances, radiation therapy may also be needed to have the best chance of cure. In other instances, cancer may have invaded critical areas, such as near the spinal cord and may be causing considerable symptoms, such as pain or weakness. Radiation therapy in these instances may also be necessary and is usually effective in “palliating” the symptoms. In some patients, the cancer may have spread widely and have gone into areas that are difficult to treat with chemotherapy, such as the brain. These metastases are often treated with radiation therapy. As discussed earlier, side effects resulting from radiation therapy for each of these situations are usually limited to the area being treated. The radiation oncologist usually selects a dose that is expected to be effective, but is also under the tolerance of the nearby normal tissues and organs, also taking into account whether chemotherapy is being administered.