On average, people who have a first cancer have a 14% higher risk of a subsequent primary cancer than the general population, according to a major monograph just released by the National Cancer Institute (NCI). The report, "New malignancies among cancer survivors," looks at two million cancer survivors over a nearly 30-year period and is called "by far the largest study to date of subsequent cancers."
Second cancers are of burgeoning public health importance, said NCI researchers at a science writers seminar introducing the data. The number of cancer survivors is growing due to earlier diagnosis, more effective treatment, and decreasing death rates from other causes.
Crystal Mackall, M.D., acting chief of the NCI pediatric oncology branch, said that whatever the causes of second cancers, "for those of us currently in the trenches, the problem is at our doorstep." These patients need specialized treatment, she contended. "You can't open an oncology textbook and be taught how to treat these patients. You want a multi-modality medical team. You need a referral center," she said at the Jan. 24 seminar on the National Institutes of Health campus in Bethesda, Md.
She noted also the example of female survivors of Hodgkin's disease who were treated with chest wall irradiation and then developed breast cancer. There is less option for conserving the breast due to risk of further radiation, she noted, and anthracyclines are largely avoided because the patients have often received cardiac irradiation.
Beyond that, there are intense psychological issues, Mackall said. Patients who develop a secondary osteosarcoma, for example, are looking at the prospect of more chemotherapy, which is part of the reason they develop secondary tumors in the first place. "So you can imagine the ambivalence everybody feels in giving them more chemotherapy, and yet it is certainly part of the regimen." Although many second cancers are treatable and curable, Mackall said, the patients require "the expertise of experienced medical teams acquainted with the management of these patients."
Also of possible pharmacy interest as more medications for addiction become available is that the monograph emphasizes that tobacco and alcohol intake seems to account for many second cancers. "More than 11,000 of the 25,000 subsequent cancers observed, following initial cancer, that are typically related to tobacco and/or alcohol (e.g. oral cavity/ pharynx, esophagus, larynx, and lung) occurred at a variety of sites also related to these exposures," according to the publication. Since numerous other studies find a lower risk for survivors who change their behavior, notably by stopping smoking or drinking, there's a need for behavioral research and educational programs to reinforce lifestyle, according to the monograph.
NCI researchers at the seminar also agreed, however, that a short intervention with a physician, such as an oncologist, even after a patient has a first smoking-related cancer, is unlikely to cause most patients to quit.
The new monograph, based on data from NCI's population-based cancer registries in its Surveillance, Epidemiology, End Results Program (SEER), looks at each of dozens of types of first cancers and compares patients' risk of getting each of dozens of other types of cancers. The data show, according to NCI, that although cancer therapy does not put older adults at substantial risk for subsequent cancers, children and young adults do seem to be "especially prone to carcinogenic effects of intensive radiochemotherapy regimens."
For example, said NCI, although the study did not look directly at the effects of chemotherapy and hormonal therapy, it did find marked increased risk for acute leukemia following first cancers that are usually treated with potentially leukomogenic agents. Further, reported the monograph, "among breast cancer patients, hormonal therapy [primarily tamoxifen] appeared to increase the incidence of cancer of the uterine corpus while decreasing the risk of contralateral breast cancer."
Other factors that may contribute to subsequent cancers, according to the monograph, include nutrition and hormones, infections and immunosuppression, and genetic disposition.