Why do some cancers suddenly grow exponentially, and what factors influence this rapid
progression?

ALL cancers grow exponentially, unless they become so large that their blood supply can
no longer keep up with their demands, in which case a lot of the cancer cells die as a
result of being starved of oxygen and nutrients, and the growth slows.

The smallest detectable cancer is about a gramme of tissue, which is roughly 1,000,000,000 cells.

Starting from a single cell that means that it has doubled in size roughly 30 times, so
working backwards from there and using the mathematics of exponential growth, and
taking a typical doubling time of an early cancer of, say, 6 months, that means that most
cancers will have been there for 10 - 20 years before they are large enough to be
diagnosed.

Another 10 doublings and there will be 1Kg of tissue, probably scattered round the body
by then in the form of metastases.
This is about as much as the body can cope with, and that amount is usually fatal.

Usually by the time a cancer becomes large enough to diagnose there have been a lot of
mutations, some of which will have increased the growth rate, so more advanced cancers often grow faster than early ones.

If a cancer is successfully treated to the point where it is no longer detectable, there still
may be up to a billion malignant cells left, which is why they often recur.

It is a curious thought that oncologists only every see the last few years of a cancer that
is there for decades.

Full story: https://www.quora.com/Why-do-some-cancers-suddenly-grow-exponentially-and-what- factors-influence-this-rapid-progression

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