Radiation Therapy for Hodgkin’s Lymphoma
Radiation therapy is an important treatment modality for patients with Hodgkin’s disease. However, radiation therapy is usually not the sole treatment for Hodgkin’s disease except in selected circumstances. Chemotherapy alone or combined modality treatment with chemotherapy and radiation therapy is typically utilized even for early stage disease. Therefore, it is essential for patients with Hodgkin’s disease to be treated at medical centers where medical oncologists, radiation oncologists and surgeons work together.
The objective of radiation therapy is to kill cancer cells for a maximum probability of cure with a minimum of side effects. Radiation is usually given in the form of high-energy beams that deposit the radiation dose into the body where cancer cells are located. 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 the radiation field, the cancer cells are not destroyed by the radiation. It is also important to realize that the treatment of Hodgkin’s disease with radiation therapy and chemotherapy is still evolving, with a trend towards the use of less radiation therapy and more chemotherapy in order to decrease the long-term side effects of radiation.
Delivery of Radiation Therapy for Hodgkin’s Lymphoma
Modern radiation therapy for Hodgkin’s lymphoma 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 radiation to areas of Hodgkin’s lymphoma.
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 of 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 material 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 15 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.”
Radiation “Fields” Used to Treat Hodgkin’s Disease
Involved Field Radiation: Patients with Hodgkin’s disease treated with radiation always receive treatment to the area where the lymphoma is located including adjacent lymph nodes. Usually a “boost” or extra dose of radiation is given to the area where the primary lymphoma was located.
Mantle Field Radiation: Mantle field radiation is administered to patients with Hodgkin’s lymphoma in the mediastinum (behind the breast bone), lymph nodes in the neck or under the armpits and is designed to encompass the area of the cancer and the common lymph node drainage. The areas irradiated include the mediastinum, some lung tissue and the lymph draining areas of the neck and armpits. Radiation oncologists attempt to avoid, as much as possible, radiation to the lungs and breast which are the most sensitive to damage.
Inverted Y: This describes radiation to the lymph nodes in front of the lower spine (para-aortic) and the groin. Each groin makes up an arm of the inverted Y.
Treatment of the spleen: The spleen is often involved with Hodgkin’s lymphoma. In the past, when radiation therapy was the primary treatment, patients had the spleen removed and radiation treatment to the area where the blood vessels were tied off. In some instances, radiation therapy is given to the spleen without removal. However, most of these types of radiation treatment have been abandoned with the development of effective systemic combination chemotherapy.
A typical course of radiation for Hodgkin’s lymphoma would involve daily radiation treatments, Monday through Friday, for 3 to 5 weeks. The actual treatment with radiation generally last 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 Hodgkin’s lymphoma 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.
Blood counts can be affected by radiation therapy but this is not usually the case in patients with Hodgkin’s lymphoma. 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.
A significant late complication following radiation treatment for Hodgkin’s disease is lung damage with fibrosis and difficulty breathing. In one study of 36 patients with stage I-IIA Hodgkin’s lymphoma treated with radiation therapy, a decrease in lung function was noted in all patients. However, this decrease in lung function appeared to improve over time and was thought to be reversible.
Hypothyroidism (abnormally low levels of thyroid hormone) is one of the more frequently encountered late complications of radiation therapy for Hodgkin’s lymphoma, occurring in approximately one-third of patients receiving radiation therapy alone or combined with chemotherapy. This is not a complication that occurs when chemotherapy alone is used to treat Hodgkin’s lymphoma. It is important for patients who have received radiation therapy to be tested on a regular basis because signs and symptoms of hypothyroidism occur very late and are subtle. Heart disease is also a late complication of radiation to the mediastinum. In one group of 157 patients receiving primary treatment with radiation to the mediastinum, 8.3% died of heart disease, which was 5 times what would have been expected for this age group. The risk of heart disease is associated with higher radiation doses and larger field sizes.
One of the major side effects of treatment of Hodgkin’s lymphoma is the development of a second cancer. These second cancers are induced by the radiation, chemotherapy or the combination of radiation and chemotherapy used to treat Hodgkin’s lymphoma. In one study of over 5,500 patients treated for Hodgkin’s lymphoma, there were 322-second cancers. Thus, 6% of all patients treated with Hodgkin’s disease developed a second cancer. These included cancers of the gastrointestinal tract, lung, breast, bone, soft tissue and leukemia. The incidence was highest in older individuals, but many treated at a younger age have not yet reached the period of risk. In another study of 1,120 patients with Hodgkin’s lymphoma, the risk of developing a second cancer at 15 years was 11.7%. The risk of developing leukemia was 1%, the risk of non-Hodgkin’s lymphoma was 3% and the risk of solid cancers was 7.7%. Treatment at a young age will ultimately result in a high incidence of second cancers following treatment of Hodgkin’s lymphoma.
The majority of patients diagnosed with Hodgkin’s disease can expect to be cured of their cancer when modern treatment strategies are appropriately utilized. Many different treatment strategies can cure patients with stage I or IIA Hodgkin’s lymphoma. The current goal of treatment is to cure patients while producing as few treatment-related side effects as possible.
Radiation Therapy for Stage IA and IIA Hodgkin’s Lymphoma
Historically, radiation therapy has been the primary mode of treatment for patients with stage I – IIA Hodgkin’s disease with a high rate of cure. One negative aspect of the use of radiation therapy in the treatment of Hodgkin’s is pre-treatment staging (determining the extent of spread of the disease), which involves extensive surgery. Because radiation is a localized therapy, its cancer killing effects exist only at the site of its placement, not throughout the body. Therefore, knowing exactly where the cancer exists, through exploratory surgery and the removal of the spleen, seemed imperative to obtain precise placement of the radiation in order to obtain optimal results. Some risk factors involved in receiving radiation therapy include, but are not limited to, the occurrence of secondary cancers, sterility, skin burns and cataracts. However, researchers from New York have recently reported promising results of patients with clinically staged Hodgkin’s lymphoma treated initially with radiation therapy alone. Clinically staged means that indirect methods, without surgery, are used to determine the extent (or stage) of the lymphoma.
Researchers at Presbyterian Hospital in New York evaluated 94 patients with stage I and IIA Hodgkin’s lymphoma. All of these patients had the extent, or stage, of their lymphoma determined by x-rays and scans. Their treatment consisted of radiation therapy to areas affected by the lymphoma that were detected by these tests. Ten percent of these patients relapsed (the cancer returned) within an average of 38 months after treatment. However, all of the patients who had relapsed were treated with chemotherapy and radiation and achieved complete disappearance of their cancer. All patients involved in this study are currently alive without Hodgkin’s lymphoma. These findings indicate that careful clinical staging and initial treatment with radiation therapy alone is a viable treatment option for patients with early stage Hodgkin’s lymphoma. Treatment with chemotherapy for patients who relapse allows the majority of patients to be cured. More recently, combinations of low-dose chemotherapy and radiation have also been used as primary treatment modalities, which may reduce some of the side effects of radiation therapy.
Radiation Therapy and Chemotherapy for Stage I-IIA Hodgkin’s Lymphoma
Historically, patients with stage I or IIA disease were successfully treated with radiation therapy alone. Radiation therapy is a “local” therapy unable to kill cancer cells outside its field of delivery. Therefore, patients with Hodgkin’s lymphoma had to undergo extensive staging with surgery and removal of the spleen (staging laparotomy) to ensure that the cancer could be adequately treated with radiation therapy alone. Full doses of radiation therapy also cause significant long-term side effects to many patients.
Chemotherapy is also capable of curing early and advanced stage Hodgkin’s lymphoma. Chemotherapy has an advantage over radiation therapy because it kills cancer cells anywhere in the body. Chemotherapy also has long-term side effects, which may be less severe than those produced by radiation therapy. Recently, patients with stage I or IIA disease have been treated with a combination of chemotherapy and radiation therapy in reduced doses. By utilizing combination therapy, high cure rates can be achieved and the long-term side effects of each treatment may be decreased. Additionally, the extensive surgical staging evaluation can be avoided. Currently a short duration of chemotherapy with ABVD (doxorubicin, bleomycin, Velban®, and dacarbazine) followed by local radiation treatment consistently cures over 95% of patients with stage I or IIA Hodgkin’s lymphoma.
Doctors in Germany designed and conducted a clinical trial that combined chemotherapy with radiation therapy and compared this to treatment with radiation therapy alone. In this clinical study, 640 patients with stage I or II Hodgkin’s lymphoma who were at a low risk of cancer recurrence were treated with radiation therapy alone or 2 cycles of chemotherapy with ABVD (doxorubicin, bleomycin, Velban®, and dacarbazine) followed by treatment with radiation.
The first interim analysis of this clinical trial has been performed in approximately 400 patients, with a minimum of almost 2 years of follow-up from treatment. This analysis shows that patients treated with the combination of chemotherapy and radiation therapy were less likely to experience cancer recurrence than patients treated with radiation therapy alone. Only one patient treated with the combination of chemotherapy and radiation therapy has experienced recurrence of cancer and 96% of patients are alive without evidence of cancer recurrence 2 years from treatment. In comparison, 17 patients treated with radiation therapy alone have experienced cancer recurrence and only 87% are alive without evidence of cancer recurrence 2 years from treatment. Analysis comparing the side effects will be forthcoming; however, both treatment approaches appear to be well tolerated.
In summary, the results of this clinical study strongly suggest that patients with early stage Hodgkin’s disease are likely to experience a higher cure rate if treated with 2 cycles of chemotherapy followed by radiation therapy compared to the historical standard treatment of radiation therapy alone.
Radiation Therapy for Advanced Hodgkin’s Lymphoma (Stage IIB-IV)
Over 70% of patients with advanced Hodgkin’s disease achieve a complete remission following initial treatment consisting of combination chemotherapy with or without radiation therapy. However, 20-30% of patients who achieve a complete remission ultimately experience cancer recurrence. The role of radiation therapy in achieving optimal control of advanced Hodgkin’s lymphoma has been controversial and there have been attempts to treat such patients with chemotherapy alone. The goal of treatment is to achieve the greatest cure rates coupled with the fewest side effects, so new combinations, doses and options are continually being explored.
In 1989, researchers in France began a clinical trial to compare chemotherapy alone with chemotherapy plus radiation therapy for treatment of patients with advanced Hodgkin’s lymphoma. They randomly allocated 559 patients with advanced Hodgkin’s lymphoma to receive chemotherapy plus total nodal irradiation (radiation therapy to lymph nodes in the chest, neck and abdomen) or chemotherapy alone. The 5-year survival without recurrence was 74% for patients who were treated with chemotherapy alone and 79% for those who were treated with chemotherapy plus radiation. Overall survival at 5 years was 94% for patients receiving chemotherapy alone and 78% for patients receiving chemotherapy and radiation therapy.
These results suggest that chemotherapy alone is superior to chemotherapy plus radiation for treatment of patients with advanced Hodgkin’s disease. The results of this study may prevent many patients from unnecessarily receiving radiation therapy and its associated side effects.
Radiation Treatment of Relapsed Hodgkin’s Lymphoma
Radiation therapy can be used with curative or palliative intent for recurrences. If the recurrences are localized and can be encompassed within a tolerable field of radiation, good results can be achieved. More often, patients with recurrent Hodgkin’s lymphoma receive radiation for palliation of local symptoms.
Strategies to Improve Treatment
The progress that has been made in the treatment of Hodgkin’s disease has resulted from development of better methods of delivering radiation, combining radiation with chemotherapy and doctor and patient participation in clinical trials. Future progress in the treatment of Hodgkin’s lymphoma will result from continued participation in appropriate clinical trials. Currently, there are several areas of active exploration aimed at improving the treatment of Hodgkin’s lymphoma.
Three-dimensional conformal radiation: Three-dimensional conformal radiation therapy is a promising approach to radiation treatment that decreases the amount of normal tissues exposed to radiation. Using computerized tomography (CT) scans and other scans, radiation oncologists have developed methods for determining the tumor size and shape in 3 dimensions. This allows high-dose external beam radiation therapy to be delivered primarily to the cancer with less damage to normal liver cells. For example, three-dimensional conformal radiation has allowed radiation oncologists to reduce by 50% the amount of radiation to the surrounding tissues.
Treatment with Radioactive Isotopes: Attempts are being made to link radioactive isotopes to substances that localize in areas of Hodgkin’s lymphoma. There have been no monoclonal antibodies identified that will localize to areas of Hodgkin’s lymphoma. However, there have been attempts to utilize radio-labeled antiferritin which does localize to areas of Hodgkin’s lymphoma. Antiferritin antibodies are linked to yttrium-90 and have produced significant responses in patients with relapsed Hodgkin’s lymphoma.