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YSPH Alumna Leads Research into Second Cancer Risks at NCI
Dr. Lindsay Morton, a 2004 Ph.D. graduate of the Division of Chronic Disease Epidemiology, recently returned to the room in LEPH where she once defended her dissertation, this time to present to faculty and students her study findings on second cancer risks among non–Hodgkin lymphoma patients. Morton is now an investigator at the National Cancer Institute (NCI), where she conducts research in its Radiation Epidemiology Branch in the Division of Cancer Epidemiology and Genetics. Second cancers are a burgeoning area of research, despite challenges such as the relatively rare occurrence of second cancers compared with first cancers, as well as the difficulty in obtaining treatment information from the first cancer, often an essential component of the research. “To study second cancers, we use the same epidemiological methods that we use to study first primary cancer research, viewed through a slightly different lens,” Morton said. Even as the ranks of cancer survivors in the United States have grown over the past three decades, survivors often contend with a higher rate of new malignancies than the general population. Non–Hodgkin lymphoma survivors face an elevated risk for “solid” cancers (e.g. lung, melanoma, kidney, bladder), as well as Kaposi sarcoma and leukemia. Because lymphomas arise from abnormalities in the white blood cells, or lymphocytes, that course throughout the body, they are more complex than more localized cancers in the breast or prostate, said Morton. Although the causes of most lymphomas are unknown, the strongest risk factor is suppressed immunity, whether genetic or acquired; exposure to infections, chemicals, radiation or hormones; or other congenital or medical conditions. The study compiled data from 11 SEER registries in the U.S. from 1992–2005, tracking patients who had survived at least one year following diagnosis of the most common NHL subtypes: diffuse large B–cell lymphoma, follicular lymphoma and chronic lymphocytic leukemia/small lymphocytic leukemia (CLL/SLL). The cohort was stratified by HIV/AIDS status at the time of lymphoma diagnosis. The 852 patients with known HIV/AIDS at the time of lymphoma diagnosis were shown to face a far higher risk for second cancers, particularly anal cancer and Kaposi sarcoma—likely due to their shared risk factors. Among the 38,485 patients without known HIV/AIDS at the time of lymphoma diagnosis, second cancer risks were much lower, but still elevated compared with the general population for survivors of CLL/SLL. Increased risks of acute non–lymphocytic leukemia and chronic myeloid leukemia among lymphoma survivors may be traced to the effects of chemotherapy, said Morton. Risk of lung cancer and melanoma was significantly increased only among patients with CLL/SLL and follicular lymphoma, whereas a decreased risk of breast cancer was seen among follicular lymphoma survivors only. Morton said the findings require a re–examination of previous research holding that second lung cancers and melanoma in lymphoma patients may be due to alterations in the immune system, radiation treatment or chemotherapy, or smoking. Instead, she said, “we hypothesize a shared underlying susceptibility to DNA damage in lung cancer, melanoma, CLL/SLL and follicular lymphoma.” Morton says she hopes to continue underscoring key differences in risk factors among the subtypes of one particular cancer. ~ Story by Melissa Pheterson |
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