Radiation – Induced Malignancies :Radiation – Induced Malignancies Christopher Estrada Jason Chok Mathew Variamattom


Objectives :Objectives List the different types of Radiation – Induced Malignancies Describe the latent periods of each malignancies Explain the dose relationships of the malignancies Describe the different types of Radiation – Induced Malignancies


What is Leukemia? :What is Leukemia? Leukemia is a general term for blood cancer. It begins in the bone marrow, where blood cells are produced and can be acute (rapid and severe) or chronic (slow and progressive). Leukemia is one of the most frequently observed radiation-induced cancers. It is responsible for approximately one-sixth of the fatalities from radiocarcinogenesis. It may be either lymphoid (in lymph tissue) or myeloid (in marrow). Leukemia can occur at any age, but is most common in people over 60.


Types of Leukemia? :Types of Leukemia? There are two main types of Leukemia, i.e., lymphocytic leukemia and myeloid leukemia. When leukemia affects lymphoid cells, it is called lymphocytic leukemia and when myeloid cells are affected, the disease is called myeloid leukemia. Leukemia is either acute or chronic. In acute leukemia, the abnormal blood cells remain very immature and cannot carry out their normal functions. In chronic leukemia, some immature cells are present, but in general, these cells are more mature and can carry out some of their normal functions.


Most common types of leukemia :Most common types of leukemia The most common types of leukemia are: Acute lymphocytic leukemia, Acute myeloid leukemia, Chronic lymphocytic leukemia and Chronic myeloid leukemia. Acute lymphocytic leukemia is the most common type of leukemia in young children. This disease also affects adults, especially those aged 65 and older. Acute myeloid leukemia occurs in both adults and children. This type of leukemia is sometimes called acute nonlymphocytic leukemia. Chronic lymphocytic leukemia most often affects adults over the age of 55. It sometimes occurs in younger adults, but it almost never affects children. Chronic myeloid leukemia occurs mainly in adults. A very small number of children also develop this disease. There are also other less common type of chronic leukemia.


Effects of Leukemia? :Effects of Leukemia? Leukemia is one of the most frequently observed radiation-induced cancers. It is responsible for approximately one-sixth of the fatalities from radiocarcinogenesis. When leukemia develops, the body produces large numbers of abnormal blood cells. In most types of leukemia, the abnormal cells are white blood cells. There are several types of leukemia. They are grouped in two ways. One way is by how quickly the disease develops and gets worse. The other way is by the type of blood cell that is affected.


Studies on radiation-induced leukemia :Studies on radiation-induced leukemia Historically, incidence of leukemia has been recorded from the atomic bomb survivors from Hiroshima and Nagasaki demonstrate a substantial increase in the incidence of leukemia when comparing the exposed with the unexposed population. From 1950-1956, 64 out of 117 new cases of leukemia were associated with radiation. In Hiroshima 61 leukemia deaths were observed as compared with the expected incidence of 12 and In Nagasaki 20 leukemia deaths were observed as compared with the expected incidence of 7. For finding out the relative risk of cases we can use the following formula: Relative Risk = Observed cases/Expected cases, here it is 61/12 = 5.08


Leukemia in the U.S. :Leukemia in the U.S. With the incidence of leukemia in the U.S. at approximately 70/10,000, it is considered a rare disease. Even so, leukemia is one of the most frequently observed radiation-induced cancers. It is responsible for approximately one-sixth of the fatalities from radiocarcinogenesis. Radiation-induced leukemia is judged to be linear, nonthreshold, and has a latent period of 4-7 years with an at-risk period of 15-20 years.


Skin Carcinoma :Skin Carcinoma Skin carcinoma means cancer that begins in skin or tissues that line the inside or cover the outside of internal organs. Within 15 years of discovery of x-rays, hundreds of cases of skin carcinoma were reported by radiology personnel. It has occurred because people were treated with radiation for acne and ringworm and developed skin cancer years later. These people were exposed to unfiltered low kV x-rays which deliver very high doses to the superficial skin layers.


Effects of Radiation-induced skin carcinoma :Effects of Radiation-induced skin carcinoma Radiation-induced skin carcinoma follows a threshold dose-response relationship, and has a latent period of 5-10 years. In the 500 to 2,000 rad range, the relative risk for skin cancer is 4 to 1. Radiation-induced skin carcinomas are not present in current radiology personnel.


Thyroid Cancer :Thyroid Cancer Thyroid cancer is responsible for approximately 12% of the deaths attributed to radiation-induced malignancies. Females have approximately a 3-5 times greater risk for radiation-induced thyroid cancer than males, because of hormonal influences on thyroid function.


Effects of radiation-induced thyroid cancer :Effects of radiation-induced thyroid cancer Radiation-induced thyroid cancers are either papillary (nipple-like protrusion) or follicular (cavity), which are usually benign and slow growing, with a mortality rate of about 5%. The latent period for benign nodules nodules is 5-35 years, and for malignant nodules 10-35 years. Internal irradiations from radionuclides such as iodine-131 have not been proven to cause thyroid cancer. The dose-response relationships for thyroid cancers are linear, nonthreshold.


Breast Cancer :Breast Cancer The United States’ breast cancer for women is approximately 85/10,000 year. With low LET radiation, breast cancer risks seems to be age dependent. So the younger you the more you are at risk. Breast cancer data appear to fit a linear dose – response relationship. The latent period varies from 10 – 40 years. Absolute risk is estimated to be approximately six cases/106 persons/rad/year.


Breast Cancer :Breast Cancer


Osteosarcoma :Osteosarcoma Osteosarcoma is the most common type of malignant bone cancer, accounting for 35% of primary bone malignancies The tumor may be localized at the end of the long bones. Most often it affects the upper end of tibia or humerus, or lower end of femur. The absolute risk is 0.11 cases/106 persons/rad/year. Osteosarcoma follows a linear quadratic dose – response relationship.


Osteosarcoma :Osteosarcoma


Lung Cancer :Lung Cancer Lung cancer is a disease of uncontrolled cell growth in tissues of the lung. This growth may lead to metastasis, invasion of adjacent tissue and infiltration beyond the lungs. Dose – response relation ship for radiation – induced lung cancer are linear nonthreshold Absolute risk of 1.3 cases/106 persons/rad/year has been calculated.


Lung Cancer :Lung Cancer


Question #1 :Question #1 What is Leukemia?


Answer #1 :Answer #1 Leukemia is a general term for blood cancer


Question #2 :Question #2 What are the two main types of Leukemia?


Answer #2 :Answer #2 The two types are lymphocytic leukemia myeloid leukemia


Question #3 :Question #3 How do we calculate the relative risk of leukemia in a study, what is the formula?


Answer #3 :Answer #3 Relative Risk = Observed case Expected cases Example: Observed = 60 Expected = 12 Relative Risk = 61/12 = 5.08


Question #4 :Question #4 What is the latent period for leukemia?


Answer #4 :Answer #4 Leukemia has a latent period of 4-7 years


Question #5 :Question #5 What is the dose – response relationship and latent period for skin carcinoma?


Answer #5 :Answer #5 Radiation-induced skin carcinoma follows a threshold dose-response relationship, and has a latent period of 5-10 years


Question #6 :Question #6 Which cancer is responsible for approximately 12% of the deaths attributed to radiation-induced malignancies?


Answer #6 :Answer #6 Thyroid Cancer


Question #7 :Question #7 What is the latent period of breast cancer?


Answer #7 :Answer #7 It varies from 10 – 40 years


Question #8 :Question #8 What is the ratio of breast cancer in the U.S.?


Answer #8 :Answer #8 The United States’ breast cancer for women is approximately 85/10,000 a year.


Question #9 :Question #9 What is the most common type of malignant bone cancer?


Answer #9 :Answer #9 Osteosarcoma is the most common type of malignant bone cancer, accounting for 35% of primary bone malignancies.


Question #10 :Question #10 What is lung cancer?


Answer #10 :Answer #10 Lung cancer is a disease of uncontrolled cell growth in tissues of the lung.


References :References http://www.google.com/search?hl=en&q=radiation+affected+Leukemia http://www.molbiolcell.org/cgi/content/abstract/10/8/2493 (2004 Aug 31). Retrieved June 10, 2008, from Radiation-induced malignancies following radiotherapy for breast cancer Web site: http://www.ncbi.nlm.nih.gov/pubmed/15292931