Hi Lolly,
The information was from various sources, but there seems to a consensus around these. So, the rough figures I used were were as follows:
1 cubic centimetre of tumour tissue contains about 1 billion (US) cells. That’s 1,000,000,000 cells. I reckon the volume of Janet’s tumour was about 5cc, as 2.5cm was the longest dimension, making about 5,000,000,000 cells.
The tumour grows by cells dividing into two each cell cycle, starting with one single bloody evil cell (that really gets me), so the number of cells will be 2 to the power of the number of cell divisions. Now, 2 to the power 32 is 4294967296, so it should have taken just over 32 cycles to reach the size it was.
The general consensus seems to be that cell division takes place roughly every 100 days, so the time to grow to this size would be 3,200 days, which is 8.77 years.
Now, having read a bit more, it seems there can a lot of variation in the time it takes for cells to divide. It seems to be from 29 days to more than 300 days, with 100 being typical. In the 29 days case, that you reduce the time to 2.5 years, but that is at the end of the likely range.
I just found a good paper on the subject at:
breast-cancer-research.com/content/10/3/R41
On reflection, I think that, although what I said is correct, it is important to understand this background because the tumour does, of course, grow faster in the later stages due to the doubling. On the other hand, the constant doubling is probably the most pessimistic estimate because as the tumour gets bigger, cells in the middle start to die due to lack of oxygen. (Until the tumour is eventually able to build itself a blood supply - it really is evil this disease.)
So, the figures are all very rough, but I think the point is that we tend to think of tumour cells frantically growing, so that every day’s delay is important, but that really isn’t the case.
Sorry it’s so long and you probably didn’t want an essay on the subject, but hope it’s useful.