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Lymphoma and Pets
Radiotherapy - Dosage
The terms you may find in your treatment for lymphoma may be different than terms used by others. While older literature may list dosage in rads, current treatment may be listed in grays. This section attempts to explain some of the terms used in lymphoma therapy and discuss what dosage may be given.
Radiation treatment for lymphoma usually comes in the form of x-rays or gamma radiation (high energy photons). The dose is usually measured in roentgens, grays, or sieverts. The roentgen (abbreviation R or rad) is the amount of x or gamma ionizing radiation in the air. The gray (Gy) is the amount of energy absorbed by a substance or tissue. The roentgen and the centigray (1/100 of a Gray abbreviated cGy) are essentially equivalent. The sievert (abbreviated Sv) equals the gray adjusted by a quality factor for the biologic effect - for x and gamma radiation the Sv equals the Gy.
If you have older records or see your treatment written differently you can make the conversion between rad and rem to gray and sievert as follows:
|1 Gy = 100 rad||1 Sv = 100 rem||1 centigray (cGy) = 1 rad|
If your chart says you are to receive 3500 cGy you know that it is also 35 gray or 3500 rads.
Dosages commonly used
This is where it becomes tricky. Radiation doses vary with each type of lymphoma and how far it has spread (among other factors). It is difficult to say that all stage 2 lymphoma patients receiving radiation therapy will be given so many centigray.
Oncolink states that radiation dosage for Hodgkin's is somewhat controversial. It is possible one hospital may decide on a dosage slightly different from another based on their experience. This is why the professional radiation therapy team works closely to assess the patient's condition and formulate a treatment plan.
One figure Oncolink used for Hodgkin's lymphoma therapy was at least 35 Gray (3500 rads or cGy). NCI stated that in adult Hodgkin's, doses of radiation usually vary between 3,000 and 3,600 cGy to clinically uninvolved sites, and 3,500 to 4,400 cGy to regions of initial nodal involvement. They also state these recommendations are often modified in pediatric or advanced-staged adult patients who also receive chemotherapy.
For Non-Hodgkin's, NCI stated: although localized presentations are uncommon in non-Hodgkin's lymphoma (NHL), the goal of treatment should be cure in those who are shown to have truly localized disease after undergoing appropriate staging procedures. Long-term disease control within radiation fields can be achieved in a significant number of patients with indolent stage I or stage II NHL by using doses of radiation that usually range from 2,500 to 4,000 cGy to involved sites or to extended fields which cover adjacent nodal sites.
In October 2005, doctors found that halving the usual dose of radiation and combining it with chemotherapy can produce high survival rates in people with early-stage Hodgkin's lymphoma. That finding was presented Monday by German researchers at the American Society for Therapeutic Radiology and Oncology (ASTRO) annual meeting in Denver, Colorado.
The researchers noted that, if caught early, Hodgkin's lymphoma can be cured and most patients live for many years after their diagnosis. However, they often have to cope with side effects of radiation treatment. The researchers wanted to examine whether those side effects could be reduced by decreasing the amount of radiation needed to treat patients.
The four-year study of 1,131 patients looked at whether reducing the amount of radiation (from 30 Gy to 20 Gy) and combining it with chemotherapy would cure the patients. More than 98 percent of the patients who received this treatment experienced complete remission, while 13 patients died from Hodgkin's lymphoma during the study, the researchers said.
"Although this was an interim study, the results are very encouraging that we can cure patients with early stage Hodgkin's lymphoma of their cancer while reducing the amount of radiation we give them, thus allowing them to have a higher quality of life after treatment," study author Dr. Hans Theodor Eich, a radiation oncologist at the University of Cologne, said in a prepared statement.
Again: dosages can and will vary from patient to patient. A qualified medical professional should be consulted.