Second bout with cancer often results from same risk factors

Cancer can, and sometimes does, strike twice. It famously happened to Justice Ruth Bader Ginsburg of the Supreme Court, who was successfully treated for colon cancer in 1999 and then for pancreatic cancer in 2011. If not for the regular checkups she underwent after colon cancer, it is quite likely that her pancreatic cancer, which is rarely found early, would not have been detected while still curable.

Depending on age, up to one in four cancer survivors is likely, sooner or later, to develop a second new cancer that is neither a recurrence nor spread of the original. Yet many survivors fail to take advantage of well-established ways to keep a future cancer at bay or take steps to detect a new cancer when it is still early enough for cure.

The matter is hardly trivial. The population at risk is huge and growing. As a result of better cancer screening and treatment and continuous aging of the population, the number of cancer survivors in the United States has increased fourfold in the last 30 years, reaching 15.5 million by 2016, and is expected to climb to 26.1 million by 2040.

Though it may seem counterintuitive, patients successfully treated for early breast or lung cancer are likely to live longer than people who never had cancer, giving them more years in which to develop a second cancer.

In a recent report in JAMA Oncology by researchers at the University of Texas Southwestern Medical Center in Dallas, approximately 25% of Americans 65 and older and 11% of younger adults who were previously treated for cancer were subsequently found to have one or more new cancers in a different site. Depending on the type of original cancer and the person’s age, the risk of developing a second unrelated cancer ranged from 3.5% to 36.9%. The study covered 765,843 new cancer diagnoses made between 2009 and 2013 and recorded in a population-based national registry, the Surveillance, Epidemiology and End Results program.

In many cases, the development of a second cancer resulted from the same risk factors that most likely precipitated the first malignancy. These factors include tobacco use, obesity and infection with human papillomavirus. For example, a smoker who has been successfully treated for lung cancer may later develop bladder cancer, which is also related to smoking, as well as a second lung cancer. An HPV infection, which most often causes cervical cancer, can also cause cancers of the vagina, penis, rectum and throat. And obesity is a known risk factor for at least 13 kinds of cancer, including cancers of the uterus, esophagus, stomach, liver, kidney, colon and pancreas.

Although much less common nowadays than in years past, sometimes the chemotherapy or radiation treatments used to control the first cancer cause genetic or other changes that lead to a new cancer. Examples include leukemia that can be induced by chemotherapy or radiation therapy, or uterine cancer caused by the drug tamoxifen used to treat breast cancer.

The Texas researchers, led by Caitlin C. Murphy, an epidemiologist, undertook the study of new cancers in cancer survivors in hopes of changing the common practice of excluding former cancer patients from clinical trials when they develop another cancer.

“This exclusion is not evidence-based,” Dr. Murphy said in an interview. “Patients with a prior cancer do not necessarily have a worse prognosis than those without a cancer history. They should be allowed to participate in clinical trials, which may be one of their only treatment options. If they’re excluded, a lot of patients are left out from what may be the best available treatment.”

Dr. David E. Gerber, a co-author and lung cancer researcher, said another message from the study was the importance of urging patients to eliminate or reduce cancer risk factors and pursue surveillance recommendations that can alert doctors to the development of a new cancer early enough for cure.

Based on his research, Gerber said that “among people found to have a Stage 4 lung cancer, 15% of them had a history of an earlier cancer.” Had they been counseled about their risk of developing a new cancer and properly monitored, they most likely would not have had such advanced disease, which is rarely curable. And if they had quit smoking after the first diagnosis, their risk of developing a new lung cancer could have fallen by almost 90%, he said.

Dr. Nancy E. Davidson, who wrote an accompanying commentary, said there were evidence-based guidelines for monitoring cancer survivors who had been treated for cancers of the breast, lung and colon.

“Just because you were successfully treated for one cancer doesn’t mean you’re not at risk for another cancer,” Davidson, of the Fred Hutchinson Cancer Research Center in Seattle, said in an interview. “There are appropriate surveillance guidelines for cancer survivors based on their age and previous diagnosis. Interventions should be tailored to the patient’s circumstances so that patients are spared unnecessary testing.”

She also emphasized the importance of counseling cancer survivors about caring for their general health. “When patients survive cancer, it doesn’t mean they won’t get heart disease, high blood pressure or diabetes,” she said.

In a previous study of 42 survivors of early-stage breast and prostate cancers, Dr. Shawna V. Hudson, medical sociologist at the Cancer Institute of New Jersey, and co-authors wrote in the Annals of Family Medicine that about “70% of cancer survivors have co-morbid conditions that require a comprehensive approach to their medical care. Survivors’ follow-up management entails more than routine surveillance for recurrence of cancer.”

After five years of survival, only about a third of cancer survivors continue to be cared for by specialists related to their original cancer, researchers at the Centers for Disease Control and Prevention have found.

Too often, Hudson’s team wrote, once they finish cancer treatment and its immediate aftermath, survivors fail to receive appropriate care from their primary care doctors. They said patients needed “a better understanding of what cancer follow-up care is, its lifelong duration, and the potential for varying degrees of monitoring.” Many of the participants in their study “were unaware that cancer follow-up care extends beyond surveillance for recurrence.”