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					                       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/2005−03/0012.html


LB_at_notmine.com
Date: 03/01/05

Date: Tue, 01 Mar 2005 06:18:15 −0500



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 not
> the same as small primary cancers, and are often incurable, and the benefit
> of finding them when they are "small" is to say the least questionable.
>
> 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 number,
> 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 − certainly
> 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 cancer
> 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 "life
> cycle". "Partial responses" may be valuable in terms of symptoms, but
> usually don't offer any survival benefits.

Re: "Early" and "Late" Cancers                                                          1
                       sci.med.diseases.cancer: Re: "Early" and "Late" Cancers
>
> 8) Even a "complete remission" may only mean that a 1kg cancer has been
> knocked back 10 generations out of 40, so that is now smaller than the
> 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, though.
> 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 considering
> responses to treatment and what they mean.

Depressing even if totally accurate:−((
OTOH complete cure IS possible. My lady had a mastectomy followed by chemo 30
years ago. That cancer has never re−appeared, Unfortunately she developed
Ovarian about four years ago and that one is "winning".

Steph; you have a series of questions to help decide if chemo is worth doing. I
wonder if that is at a web site. If it is perhaps you could add the link to
your sig.
I believe I learned about it from a post by J.
If there is a site the link should be of the form http://www.anywhere.xxx which
makes it a hot link in almost all readers

TIA
LB




Re: "Early" and "Late" Cancers                                                    2

				
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