Cancer’s invasion equation – Will a tumor spread? That may depend as much your body as on your cancer

As I’m growing older and seeing loved ones go and cancer becoming a closer reality, this article on this new focus in research around the host tissue “soil” rather than “seed” really picked my interest.


It certainly hit the nail head on with questions I always ask myself (given how I’m often the one getting sick after a public transport episode):

You ride the subway one morning. The train is delayed at Fifty-ninth Street, and a man in a Yankees cap sneezes on you. At work later that week, you feel the chill entering you quietly, on little cat feet. You take a cab home, now sniffling, cursing the C line and retracing your steps: the culprit with the cap; the empty seat that should have raised suspicion; that slightly moist steel bar you should never have touched. What you do not think about are the six other passengers, sitting nearby, who also got sneezed on. None of them are sick.

This is medicine’s “denominator problem.” The numerator persists. The denominator vanishes. Why didn’t the denominators get sick? The pathogen exposure was the same; the hosts were different.

The story of Anna Guzello, a supermarket cashier from Brooklyn, who has a mother with a severe disability to care for, and few vacation days really resonated with me. What would I do in her situation? She had a total mastectomy of the breast, the surgeons had removed the tumor and was

N.E.D.: “no evidence of disease.”

Unfortunately, the issue is that evidence refers to the state of our knowledge, not the state of the disease. Even with NED, women can relapse with metastatic breast cancer months, years, or even decades later (Breast-cancer cells could have escaped and settled in brain, spinal cord, or bones, where they might be invisible to scans and tests). Patients who succumb to cancer generally die of these metastases, not of their primary tumors. So treatments aim decrease the chance of metastasis—the growth of cancer cells in sites outside the breast. Anna just said something very obvious:

“If I don’t have those metastases, then I’ll be taking risks for no reason,”

Was there any way to know whether she was likely to suffer metastasis? “Then I’d be able to assess the risks and benefits more realistically,”

Unfortunately, we don’t know: Only some fraction of patients who receive toxic chemotherapy will really benefit from it, but we don’t know which fraction.

I truly believe that our metabolisms are not created equal and in the deep roots to the idea that a cancer’s metastases depend on local habitats.


The other interesting angle in this article is the unfulfilled promise of early detection and the story of an epidemic-that-wasn’t.

In South Korea, starting about fifteen years ago, doctors began to screen aggressively for thyroid cancer. Primary-care offices in Seoul were outfitted with small ultrasound devices, and doctors retrained themselves to catch the earliest signs of the disease. When a suspicious-looking nodule was found, it was biopsied. If the pathology report was positive, the patient’s thyroid gland was surgically removed.

By 2014, thyroid-cancer incidence was fifteen times what it was in 1993 [..] a “tsunami of thyroid cancer”. […] Yet the rate at which people died from thyroid cancer remained unchanged. The patients had been […] overdiagnosed.

It seems counter-intuitive to read about over diagnostics but then this experiment in 1985, in Finland autopsied a group of a hundred and one men and women who had died of unrelated causes—car accidents or heart attacks and found thyroid cancer in more than a third of the glands inspected. This suggests that hyperzealous early-detection program might overdiagnose breast cancer with startling frequency, leading to needless interventions.

Wow, just like that.

“It’s not just early detection that we want to achieve,”. “It’s early prediction.”

Early detection helped us with when and what but not with whether.

That’s what Anna is worried about in the difficult decision she has to make.

We err toward risk aversion, even at the cost of bodily damage; we don’t learn what would happen if we did nothing.

I would be the 1st one to ask: “Would you sit and do nothing if someone found this tumor in you?”

Anna refused the chemo.

Suppose we could install tiny sensors in people which would regularly scan their blood to find circulating tumor cells, conducting an ongoing “liquid biopsy.” We’d be catching cancers earlier than ever before. But, as with the doctors in Seoul, we might also end up overtreating more cancers than ever before.

Why don’t the mets take hold? The old answer was: the cancer wasn’t the right kind of guest. The new question is: should we be looking, too, for the right kind of host?

We thought there was a roll-of-the-dice aspect to falling ill. There absolutely is.

But what Medzhitov calls “new rules of tissue engagement” may help us understand why so many people who are exposed to a disease don’t end up getting it.

By talking about cancer in ecological terms, [researchers] pay more attention to the soil.

There are important consequences of taking soil as well as seed into account. Among the most successful recent innovations in cancer therapeutics is immunotherapy, in which a patient’s own immune system is activated to target cancer cells.

Even if “holistic” has become a patchouli-scented catchall for untested folk remedies; as ambitious cancer researchers study soil as well as seed […] the true meaning of “holistic” returns: to take the body, the organism, its anatomy, its physiology as a whole.

Once we think of diseases in terms of ecosystems, then, we’re obliged to ask why someone didn’t get sick. Clinically speaking, it’s tough to study those who haven’t fallen ill.

That makes sense, although I never thought about it before, it’s harder to isolate the ones who in majority don’t fall sick.