Wondering What Caused the Cancer

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Credit Stuart Bradford

“But what caused it?” my patient asked, referring to the failure of her bone marrow to make the blood cells the rest of her organs craved. She was profoundly anemic and seemed to tire from even asking the question.

Dozens of my patients have asked the same thing. Even a dozen dozen.

I think the question reflects a human desire to revisit events that occurred over a lifetime, and speculate whether a change in course could have avoided an untoward outcome.

In truth, though, except in very rare cases, it is almost impossible to say that a specific environmental exposure triggered a given person’s cancer. The majority of cancers arise randomly, as if thumbing their nose at our collective need to find a cause.

But that doesn’t stop me from trying, during the part of the clinic visit when it’s my turn to ask the questions. And sometimes, I even convince myself that I have uncovered that nugget of truth that explains disease.

One patient, a man in his 70s, told me he served in the military.

“Which branch?” I inquired.

“Navy,” he said proudly.

“Did you see any action?” I asked.

He glanced at his wife briefly, as if checking in with her that it was all right to tell this story she had probably heard hundreds of times before. She nodded slightly, giving her permission.

“I was on one of the ships that was active during the Cuban Missile Crisis,” he said.

“Wow!” I said, incredulous. “What was that like?”

“Hot,” he answered, laughing. “And humid. It was like a living hell.”

I shook my head in disbelief, not saying anything, encouraging him to go on.

“Yeah, in fact, the only way my buddy and I could escape the heat was at night. Instead of lying in our bunks, we put a mattress on the ground in the hull, in between these two metal cases. The metal was cool at night. They kept the nuclear weapons in those cases.”

A nuclear arsenal a foot from his bone marrow. Perhaps, more than 50 years ago, that was the culprit. Though I’ll never really know for sure.

Another patient, a few years ago, told me she used to live in Nevada.

“Any exposures to chemicals or radiation you’re aware of?” I asked her, as I ask all of my patients.

“Not that I can think of,” she answered, and then chewed on her lip as she thought about it. I stayed quiet.

“Well,” she started chuckling to herself. “I used to live in Nevada in the 1950s. And I remember a couple of times that fliers would be posted on the telephone poles inviting the entire town outside to watch the huge mushroom cloud that would follow the nuclear bomb testing nearby. So we’d all stand outside and watch, and then the hot winds from the explosion would pass through the town, almost knocking us over.”

I pictured the radioactive breeze, encircling her impressionable bone marrow stem cells when she was just a girl.

I’ve had patients who describe working in shoe stores where they would take an X-ray of a customer’s foot as a gimmick to measure them for the perfect-fitting shoe, without a lead vest for protection. Or of being employed by a tire manufacturer and soaking, day in and day out, in a vat of benzene, a chemical we now know to be a potent carcinogen. Even my uncle once revealed to me that the acne on his back was treated with radiation in the late 1940s. He died of leukemia a few years ago.

Is it possible that these exposures, which occurred decades earlier, could have initiated the cancer that reared its head in my septuagenarians and octogenarians?

Investigators at the Atomic Bomb Disease Institute, established in 1962 in Nagasaki, Japan, have followed survivors of the bomb we dropped in 1945 to study late effects of radiation on the human body. They even have information on precisely where each person was, in relation to the bomb’s epicenter, to measure how much radiation that person was exposed to. In one study, they examined the incidence of myelodysplastic syndrome, a type of bone marrow cancer, in people given the diagnosis between 1985 and 2004. Those who were closest to the explosion, who received higher doses of radiation and who were younger when the bombs were dropped were at highest risk of developing the cancer. The median age at the time of exposure to radiation was 9, and at the time of the myelodysplastic syndrome diagnosis was 71.

It isn’t entirely crazy, then, to think that toxic events that occurred when my patients were young could have induced damage to their bone marrow that remained quiescent until they were well past retirement age.

Or maybe I’m being just as eager as my patients in grasping for any etiology for their cancer other than “dumb luck.” As if identifying a cause would enable me somehow to control it better.

Dr. Mikkael Sekeres is director of the leukemia program at the Cleveland Clinic. Follow him on Twitter @MikkaelSekeres.