Military metaphors are commonplace when people talk about cancer — or should we say the “fight against cancer.” Since John McCain announced his brain cancer diagnosis, the senior senator from Arizona has received a barrage of supportive statements featuring martial language. Politicians and other well-wishers have explicitly connected his war hero reputation with a favorable outcome. “Cancer doesn’t know what it’s up against,” former president Barack Obama tweeted. Vice President Pence wrote: “John McCain is a fighter & he’ll win this fight too.”

McCain’s daughter Meghan posted a tribute on Instagram, saying: “Cancer may afflict him in many ways: But it will not make him surrender. Nothing ever has.”

On television, newscasters discussing McCain’s diagnosis talked up his toughness, too. “There is nobody who is the kind of fighter that John McCain is,” said CNN’s Dana Bash. “. . . He has a fighter pilot’s mentality.”

There’s no denying McCain’s fortitude. It was on full display this past week, when he bucked his party to block the repeal of the Affordable Care Act. But can personality traits alter the course of cancer, as his well-wishers seem to want to believe? Can a positive mental stance tame an aggressive malignancy such as glioblastoma ?

As a doctor and cancer survivor, I know there is no evidence to support the idea that personality can influence the growth of malignant cells. There is no cancer for which attitude can halt the progression of disease. And, despite medical progress against other tumors, glioblastoma remains lethal. Even with treatment, patients have a slim chance of living long with this condition; the five-year survival rate is just over 5 percent. Both Sen. Ted Kennedy (D-Mass.) and former vice president Joe Biden’s son Beau died within two years of diagnosis.

Still, the words of support for McCain shouldn’t be written off as empty platitudes — phrases that belong on Mylar balloons, as the Atlantic’s James Hamblin suggested. Language can be a powerful tool in medicine. As with physical remedies, there are potential harms and risks to consider, but potential upsides, too.

The questionable relationship between cancer and psychological traits has percolated through scientific and popular literature for decades.

In her landmark 1978 essay, “Illness as Metaphor,” Susan Sontag railed against the view, popularized by psychoanalyst Wilhelm Reich, that cancer is “a disease following emotional resignation — a bio-energetic shrinking, a giving up of hope.” Sontag wrote: “Widely believed psychological theories of disease assign to the luckless ill the ultimate responsibility both for falling ill and for getting well. And conventions of treating cancer as no mere disease but a demonic enemy make cancer not just a lethal disease but a shameful one.” She rejected these notions.

Modern researchers have debunked the idea that negative emotions heighten an individual’s susceptibility to developing cancer, or that maintaining a positive outlook can stave off cancer’s return or delay its progression. As Jimmie Holland, a psychiatrist at New York’s Memorial Sloan Kettering Cancer Center, has said, “The idea that we can control illness and death with our minds appeals to our deepest yearnings, but it just isn’t so.”

In 2007, the Radiation Therapy Oncology Group confronted the belief that psychology affects cancer patients’ survival. This well-established clinical-trials organization studied more than 1,000 patients with head and neck cancers. After controlling for tumor stage and demographic factors, such as income, the researchers found no relationship whatsoever between patients’ outcomes and their emotional well-being.

Another informative, large study drew on personality questionnaires completed by nearly 60,000 Swedish and Finnish people. Years later, investigators identified 4,631 cancer cases among the participants. In 2010, they reported that neither “extraversion” nor “neuroticism” increased the likelihood of a cancer diagnosis or survival after a cancer diagnosis.

Although a handful of studies have found that women who are anxious or depressed are more likely to suffer recurrences of breast cancer and die from the condition, it’s plainly true, and understandable, that dying women are more likely to be anxious and depressed. These analyses are confounded by the fact that attitudes influence patients’ treatment decisions: their willingness to participate in clinical trials, try new drugs, seek second opinions and travel for their care.

What’s more, social determinants of health — education and economic circumstances — can mask what might be construed as grit or a fighting spirit. Many people cannot afford to try new cancer medications or seek multiple opinions. In some disadvantaged communities, fatalism about cancer affects whether patients get screened, go for checkups upon noticing worrisome symptoms or, even after a diagnosis, accept care provided by oncologists.

Meanwhile, some doctors and advocacy groups worry about the potential harms of applying battle language to the experience of having cancer. Patients may feel they are to blame if they fail to “beat” the tumor. They may think that their recurrence, or impending death, is not due to the nature of their malignancy but a failure of will.

An added concern is that military language and tales of courage can discourage acceptance of palliative care. Patients may become trapped by a positive mentality — pressured by family and friends who encourage them to keep trying more treatments, or compelled by an internal drive to fight to the end — and they may push themselves beyond what’s sensible or realistic.

Yet I recall some of my patients who liked to say they were “fighting” cancer. So did my father, who lived with lymphoma for three decades before dying at age 83 from a pancreatic tumor. When I received my own breast cancer diagnosis, in 2002, I didn’t think of it in terms of battle language. I’m not a military-oriented person; although I aspire to mental fortitude, fighting words don’t suit me. However, I accept that just as some people derive strength and comfort in prayer and others don’t, patients’ responses to words, images and stories about cancer do vary.

Recent research suggests that participating in support groups can reduce cancer patients’ anxiety, fatigue and depression. We can’t dismiss the possibility that embracing an optimistic attitude toward cancer may help some individuals to feel happier and enjoy a better quality of life even while bad cells grow and spread.

McCain may be one of those people. He displayed a battling mind-set this past week, telling his Senate colleagues that, after treatment, “I have every intention of returning here and giving many of you cause to regret all the nice things you said about me.”

McCain’s diagnosis serves as a reminder that cancer does not discriminate; everyone is vulnerable. But he also has the potential to inspire and improve the lives of other cancer patients.

When I heard about his diagnosis, I thought of the portrait of McCain that David Foster Wallace wrote for Rolling Stone in 2000. The description of the senator as a young Navy pilot is especially memorable. As Wallace tells it, in October 1967, McCain was flying a bombing mission over Hanoi when his plane was hit by enemy fire. He ejected from the craft, breaking his arms and a leg before landing in a lake. “The crowd pulled him out and then just about killed him,” Wallace wrote. “. . . McCain got bayoneted in the groin; a solider broke his shoulder apart with a rifle butt.” When he arrived at the infamous Hoa Lo prison, “they made him beg a week for a doctor and finally set a couple of the fractures without anesthetic.”

Months later, McCain was offered the chance to leave. Evidently the North Vietnamese sought to appease his father, Adm. John S. McCain Jr., who’d been promoted to lead Pacific naval forces. John S. McCain III, “100 pounds and barely able to stand, refused,” Wallace wrote. He didn’t want to violate the code that prisoners who had been detained longer should be released first. And so he spent much of the next four years alone in a small, dark “punishment cell.”

Just as his bravery 50 years ago can inspire people who have never fallen from a plane into a hostile crowd, been imprisoned or experienced torture, McCain might now set an example for others, including patients who are less strong, less fortunate and with fewer resources, as he moves forward and chooses his treatment.

Perhaps he’ll find a way to avoid entrapment by the tyranny of positive thinking. It takes a certain strength, and maybe even fierceness, to select a plan of care that doesn’t necessarily match the expectations of family, doctors and the public. He might opt for aggressive glioblastoma treatment. He might be brave enough to choose a palliative care plan, with or without potentially curative therapy. For sure, McCain will find support among Americans, who admire him for his years of service and his courage.

Twitter: @ESchattner

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