In January 2021, mathematician Hannah Fry was diagnosed with cervical cancer. When she received her diagnosis, the oncologist told her there was still uncertainty whether the cancer was already at stage three and had spread to the lymph nodes. If it hadn’t, Fry’s chances of survival were 90 percent. If it had spread, however, those odds were about 60 percent. “It looked as though the cancer was in four of the nodes, but we weren’t totally sure,” she says. “The surgeons decided to do a very radical and aggressive surgery. They essentially took out about a third of my abdomen.”
Even though Fry was obviously concerned, she also struggled with the calculation of risk involved in deciding whether to undertake a specific cancer treatment. “These are not nice treatments—they have life-changing repercussions,” she says. “With cancer, you’re often fighting an invisible enemy that may or may not be there. And even if it is there, it may or may not pose a real threat.”
This assertion is backed by evidence. For instance, in the 1970s a group of Danish pathologistson 77 recently deceased women. They had died of various causes, such as heart attacks or car crashes, and had never been diagnosed with cancer. The researchers performed double mastectomies to search for signs of cancer and found abnormal tissues—cancerous or precancerous—in approximately 25 percent of the group. “This is an astonishing result,” Fry says. “This experiment has been repeated over and over for all different kinds of cancers, like prostate cancer and thyroid cancer. The best estimates that we have now indicate that between 7 and 9 percent of us, at any point in time, are wandering around with cancer in our bodies that we have no idea about.”
Although this statistic sounds terrifying, Fry contextualizes it with another number: This is only about 10 times the number of people who end up getting diagnosed with cancer. “What this means is that, most of the time, our bodies are actually quite good at finding cancer cells and killing them and removing them,” she says. “Even when our bodies fail on that, quite often the cancer is so slow-growing that you will die of something else.”
In another, researchers looked at around 1,600 men who had been diagnosed with prostate cancer. This cohort was split into three groups: one group received surgery, another radiotherapy, and a third didn’t receive any medical intervention but was instead regularly monitored. “At the end of this study, after a number of years, there was no difference in overall survival,” Fry says. “And yet the people who received a medical intervention were left with problems like erectile dysfunction, incontinence, and bowel problems due to the radiotherapy.” A , in South Korea, looked at the effect of a national screening program for thyroid cancer on mortality rates. The conclusion was the same: Even though the number of diagnoses and treatments went up, the mortality rate remained the same.
Fry recalls when, during the course of her treatment, she visited a cancer clinic. There she met a woman in her mid-sixties who had just had a lump removed from her breast. Her oncologist talked her through the options, explaining that although they had removed all the cancerous tissue that they could detect, there was always the possibility of a recurrence, which could then be incurable. The doctor then gave her two options: continuing with chemotherapy or stopping the treatment. Her chances of survival were already very good—84 percent. Statistically, treatment would increase those odds by only 4 percent. “She was obviously very frightened,” Fry says. “She told me, ‘OK, I’ve thought about it, I’m going to have the chemo, because otherwise I’ll die.’” Fry was stunned. Was enduring such a harsh medical treatment worth the cost of such a marginal improvement in her survival rate?
Fry understands that, in the face of a scary cancer diagnosis, it’s often hard to make a rational decision based on statistical considerations. She had to go through the same process of decision. And although she considers herself one of the lucky ones—she’s been disease-free for nearly two years—because of treatment she now suffers from lymphedema, a chronic condition that makes her lower limbs swell. “Although we didn’t know at the time, we took a very risk-averse route that we didn’t need to,” she says. “It’s not really about regret. It’s just that I feel like the calculation was made without me having the chance to put what I really cared about into the equation.”
This article appears in the July/August 2023 edition of WIRED UK magazine.