Among survivors of the most common types of cancer, bladder cancer survivors had the highest risk for developing a second primary cancer, with lung cancer being the leading type, according to a recent study.
Second malignancies are not only very common among cancer survivors but also highly lethal, researchers found.
“In 2012, there were 14 million cancer survivors in the United States, and that number is expected to reach close to 20 million by 2024. Our study underscores the point that there is a large cohort of patients who will develop a second primary cancer and die from it,” lead author Nicholas Donin, MD, told Urology Times.
“In addition, it is one of the first studies to formally show a connection between lung cancer and bladder cancer. Although the finding may not be surprising considering that a smoking history increases risk for both types of cancers, it is important because it should alert urologists to how common and dangerous lung cancer is as a second primary malignancy among bladder cancer survivors and raise awareness that there is Level 1 evidence to show that screening for lung cancer saves lives,” added Dr. Donin, of the University of California, Los Angeles, working with Karim Chamie, MD, and co-authors.
For the study, which was published online in Cancer (July 5, 2016), the authors used the Surveillance, Epidemiology, and End Results database to identify 2,116,163 adults who were diagnosed between 1992 and 2008 with a primary malignancy from the 10 most common cancer sites (prostate, breast, lung, colon, rectum, bladder, uterus, kidney, melanoma, and non-Hodgkin lymphoma). During a mean follow-up of 7.1 years, 170,865 patients—1 in 12—developed a second primary malignancy, defined as a cancer with a different pathologic diagnosis diagnosed >1 year after the first malignancy. Lung cancer was the most common type of second primary cancer, accounting for 18% of those malignancies.
Among bladder cancer survivors, 19% developed a second primary malignancy within 10 years of their primary cancer diagnosis and 34% developed a second primary malignancy after 20 years. Lung cancer accounted for 25% of the second primary malignancies.
Cancer was the leading cause of death among patients who developed a second primary malignancy across all primary malignancy subgroups. Overall, more patients who developed a second primary malignancy died of their second primary malignancy than of their first (55% vs. 13%); the rates of death from second and first primary malignancies were similar among bladder cancer survivors (54% and 11%, respectively). Lung cancer accounted for 12% of deaths in patients with two primary malignancies and 57% of patients who developed second primary lung cancer died from that second primary lung cancer.
Based on findings from multiple randomized clinical trials, screening for lung cancer is now recommended in adults aged 55 to 80 years with a 30 pack-year smoking history and who are current smokers or quit within the last 15 years. Whether or not screening for lung cancer should be done routinely in survivors of bladder cancer or other cancers regardless of their smoking history is a question that will need to be answered by further research, Dr. Donin said.
“Trials demonstrating the benefit of lung cancer screening for reducing mortality excluded patients with a prior malignancy, so we don’t necessarily know if the findings from those trials are applicable to this patient population. It has also been shown that the number needed to screen to prevent mortality decreases significantly using more selective selection criteria that includes people with higher risk,” Dr. Donin said.
“Currently, therefore, we are conducting research exploring the hypothesis that there may be certain subcohorts of bladder cancer patients who are at extremely high risk for developing lung cancer. Perhaps lung cancer screening would be justified independent of smoking history in such a cohort.”
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