Siddhartha Mukherjee in The New Yorker:
One evening this past June, as I walked along the shore of Lake Michigan in Chicago, I thought about mussels, knotweed, and cancer. Tens of thousands of people had descended on the city to attend the annual meeting of the American Society of Clinical Oncology, the world’s preëminent conference on cancer. Much of the meeting, I knew, would focus on the intrinsic properties of cancer cells, and on ways of targeting them. Yet those properties might be only part of the picture. We want to know which mollusk we’re dealing with; but we also need to know which lake.
A few weeks before the ASCO meeting, at Columbia University’s hospital on 168th Street, I met a woman with breast cancer. Anna Guzello, a supermarket cashier from Brooklyn, had noticed a small lump in her left breast a few months earlier. (I’ve changed some of her identifying details.) A mammogram then revealed a hazy, spidery mass, and a biopsy confirmed that the tumor was malignant. Guzello had a total mastectomy of the breast—a simple lumpectomy would not have sufficed, given the size and the location of the mass—and planned to have surgical reconstruction. On an afternoon in May, she came to see Katherine Crew, a breast oncologist at Columbia, to discuss the next steps in her treatment. Crew’s office, on the tenth floor of the hospital, is a small, square, sparsely furnished room. The light from a fluorescent desk lamp was flickering, and Crew switched it off. She wanted no distractions. Guzello, her hair coiled into a tight bun, leaned forward, frowning intently, as Crew drew pictures and wrote notes on a sheet of paper. “Can you read my writing?” Crew asked. “You can keep the notes and always come back with questions.” Her tone was gentle, but it was as if the weight of every word were multiplied. Guzello nodded. She drummed her fingernails on the table, producing a staccato, military sound—click-click-click—a nervous tic that seemed to calm her.
“First, the good news,” Crew said. “There’s no visible cancer left in your body.” The surgeons had removed the tumor, with wide margins on all sides. The lymph nodes in the armpits—a frequent site of cancer metastasis—also contained no sign of cancer. In oncology parlance, Guzello would be classified as N.E.D.: “no evidence of disease.” But that’s a squirrelly phrase: “evidence” refers to the state of our knowledge, not the state of the disease. Breast-cancer cells could have escaped and settled in Guzello’s brain, spinal cord, or bones, where they might be invisible to scans and tests. Women with complete mastectomies and “no evidence of disease” can relapse with metastatic breast cancer months, years, or even decades after the removal of the primary cancerous mass. Patients who succumb to cancer generally die of these metastases, not of their primary tumors. (Notable exceptions are brain cancers, which can kill patients by occupying the skull, and blood cancers, in which the cancerous cells are inherently metastatic.)