sci.med.diseases.cancer: Re: "Early" and "Late" Cancers

                      Re: "Early" and "Late" Cancers

Source: http://sci.tech−archive.net/Archive/sci.med.diseases.cancer/2005−03/0027.html

Date: 03/02/05

Date: 1 Mar 2005 18:03:43 −0800

I really wonder how useful it is to think in these terms.

The definition of an advanced cancer here seems to be anything that is
detectable. A 1cm breast cancer lump would be advanced by your
(being 3/4 of the way through a cycle which could ultimately kill the
but as far as the patient is concerned surely such a tumour is in its
early stages and could be very curable. I don't think it would be
particularly useful − or meaningful − to tell such a patient that their
cancer is advanced.

With regard to treating advanced cancers − I struggle with the idea
that reducing a 1kg tumor down to 500g is not a significant event. I
only a few doublings have been lost, but how meaningful is this really?
If 1kg of cancer in a patient's liver will cause liver failure and
surely a reduction to 500g would delay this? Surely reductions in
bulk, whilst certainly not equivalent to cure, are important in terms
of how long a patient will survive?

Steph wrote:
> I've posted on this topic before, but there have been a lot of posts
> recently about "small" and "early" cancers, and the purported
benefits of
> catching primary cancers and recurrences early.
> Now, all other things being equal, it is certainly more likely that a

> primary cancer can be cured when it is smaller rather than larger,
but the
> issue is rather more complex. Recurrences after primary treatment are
> the same as small primary cancers, and are often incurable, and the

Re: "Early" and "Late" Cancers                                                          1
                      sci.med.diseases.cancer: Re: "Early" and "Late" Cancers
> of finding them when they are "small" is to say the least
> 1) Cancers start (presumably) with a single "clonogenic" cell. This
> multiplies by dividing, so the second generation is 2 cells, the
third is 4,
> the fourth is 8, etc, etc. This is called geometric growth.
> 2) The smallest cancer detectable reliably by modern imaging
techniques is
> about 1cm in size, let's say 1 cc in volume, 1 gram in mass.
> 3) A 1cm cancer contains about 10^9 cells. In order to get to this
> the original cancer cell has produced about 30 generations of
progeny, so
> the cancer is 30 generations old.
> 4) A cancer weighing 1 kilogram is likely to be a threat to life −
> a cancer of 2 kg would be. This means the total cancer, primary and
> metastases lumped together.
> 5) For a 1gram cancer to become a 1 kilogram cancer only requires 10
> doublings. For 2 kilograms, only 11 doublings.
> 6) So a 1 gram cancer is already 3/4 through it's natural life
cycle, and
> in that sense is already an "advanced" cancer.
> 7) If a treatment leads to a partial response, it maybe knocks the
> back 2 or 3 doublings. That would shrink a 1kg cancer to 500gm, or
250 gm.
> Very impressive, but not very meaningful in terms of the cancer's
> cycle". "Partial responses" may be valuable in terms of symptoms, but

> usually don't offer any survival benefits.
> 8) Even a "complete remission" may only mean that a 1kg cancer has
> knocked back 10 generations out of 40, so that is now smaller than
> limits of resolution of our imaging. Some complete remissions are
cures, but
> many are not.
> 9) These maths assume a "perfect" cancer. There is no such thing,

Re: "Early" and "Late" Cancers                                                  2
                      sci.med.diseases.cancer: Re: "Early" and "Late" Cancers
> All cancers lose cells which die − in many cancers this proportion
can be
> 90% or more − so a 1 cm cancer may be older than 30 generations, and
a 1 kg
> cancer may be much older than 40 generations.
> I believe this is something people need to think about when
> responses to treatment and what they mean.

Re: "Early" and "Late" Cancers                                                  3

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