But could there be some minimal number of treatments that could be deployed to treat a majority of these cancers effectively and less expensively? More than any other scientist, perhaps, Bert Vogelstein, a cancer geneticist at Johns Hopkins University, has tackled that conundrum. The combination of genetic mutations in any individual cancer is singular, Vogelstein acknowledges. But these genetic mutations can still act through common pathways. Targeting pathways, rather than individual genes, might reorganize the way we perceive and treat cancer.

Imagine, again, the cell as a complex machine, with thousands of wheels, levers and pulleys organized into systems. The machine malfunctions in the cancer: Some set of levers and pulleys gets jammed or broken, resulting in a cell that continues to divide without control. If we focus on the individual parts that are jammed and snapped, the permutations are seemingly infinite: Every instance of a broken machine seems to have a distinct fingerprint of broken cogs. But if we focus, instead, on systems that malfunction, then the seeming diversity begins to collapse into patterns of unity. Ten components function, say, in an interconnected loop to keep the machine from tipping over on its side. Snap any part of this loop, and the end result is the same: a tipped-over machine. Another 20 components control the machine’s internal thermostat. Break any of these 20 components, and the system overheats. The number of components — 10 and 20 — are deceptive in their complexity, and can have endless permutations. But viewed from afar, only two systems in this machine are affected: stability and temperature.

Cancer, Vogelstein argues, is analogous. Most of the genes that are mutated in cancer also function in loops and circuits — pathways. Superficially, the permutations of genetic flaws might be boundless, but lumped into pathways, the complexity can be organized along the archetypal, core flaws. Perhaps these cancer pathways are like Hollywood movies; at first glance, there seems to be an infinite array of plot lines in an infinite array of settings — gold-rush California, the Upper West Side, a galaxy far, far away. But closer examination yields only a handful of archetypal narratives: boy meets girl, stranger comes to town, son searches for father.

How many such pathways, or systems, operate across a subtype of cancer? Looking at one cancer, pancreatic, and mapping the variations in mutated genes across hundreds of specimens, Vogelstein’s team proposed a staggeringly simple answer: 12. (One such “core pathway,” for instance, involves genes that enable cells to invade other tissues. These genes normally allow cells to migrate through parts of the body — but in cancer, migration becomes distorted into invasion.) If we could find medicines that could target these 12 core pathways, we might be able to attack most pancreatic cancers, despite their genetic diversity. But that means inventing 12 potential ways to block these core paths — an immense creative challenge for scientists, considering that they haven’t yet figured out how to target more than, at best, one or two.

Immunological therapies provide a second solution to the impasse of unlimited diversity. One advantage of deploying a patient’s own immune system against cancer is that immunological cells are generally agnostic to the mutations that cause a particular cancer’s growth. The immune system was designed to spot differences in the superficial features of a diseased or foreign cell, thereby identifying and killing it. It cares as little about genes as an intercontinental ballistic missile cares about the email addresses, or dietary preferences, of the population that it has been sent to destroy.

A few years ago, in writing a history of cancer, I interviewed Emil Freireich. Freireich, working with Emil Frei at the National Cancer Institute in the 1960s and ’70s, stumbled on the idea of deploying multiple toxic drugs simultaneously to treat cancer — combination chemotherapy. They devised one of the first standard protocols — vincristine, Adriamycin, methotrexate and prednisone, known as VAMP — to treat pediatric leukemias. Virtually nothing about the VAMP protocol was individualized (although doses could be reduced if needed). In fact, doctors were discouraged from trying alternatives to the formula.