HOW LONG HAS THIS TUMOR BEEN THERE?

In every case, it has been there for some years. Most probably 10 or 20 years! It seems incredible, but to understand concept we only need to make a few calculations. 

Before it can be discovered, a tumor must be of a certain size, below which it is impossible to detect.

For example, it is very difficult to feel a small nodule of 3-5 mm in the breast, in the skin, or in a lymph node in the neck. When it reaches a size of 1 or 2 cm, it can usually be felt fairly easily by the fingers. If, however, it is in the internal organs of the abdomen or chest, such as the intestine, ovary, liver, or lung, a nodule of 1-2 cm is very unlikely to be detectable, or to cause problems. In these organs, the nodule usually begins to cause trouble when it is at least 4-5 cm in size.   

In the light of the above considerations, the following information enables us to explain why a tumor takes so many years to become detectable. We know that:

  • a tumor develops from a single cell that divides continuously;
  • a small nodule of 1 cm contains about 1 billion tumor cells;
  • the tumor cells take from 1 to 6 months to divide, and therefore to double.

If the doubling time of the tumor is about 3 months (an average between 1 and 6 ( this is a realistic approximation), it means that:

  • 1 cell splits into 2 in about 3 months;
  • 2 cells become 4 in 6 months;
  • 8 in 12 months;
  • 16 in 24 months, and so on.

This means that, to reach the number of 1 billion, the cells will have to double about 30 times (each time in 3 months), FIGURE 25. Therefore, it will take almost 10 years (3 months multiplied by 30 divisions) to form a nodule of about 1 cm.

Fig 25. Tumors grow very slowly: it takes 5-10-20 years for a nodule to grow big enough to be seen on imaging tests.

But beware! After another two divisions, which means after only another 6 months, the nodule will increase in size to 2 cm and then to 4 cm FIGURE 26.

Fig 26. Then, when the tumor becomes visible, it grows rapidly

This is why we may hear someone say, “I had an x-ray 6 months ago and there was nothing there; but now there’s a mass of 4 cm! How is it possible? Unfortunately, it is possible. 

As mentioned above, a doubling time of 3 months is an approximate estimate. Indeed, the time needed for a tumor to double in size may be longer or shorter, which explains many clinical situations that are otherwise difficult to understand.   For example, it explains why some tumors appear to remain relatively unchanged for long periods, while others seem to “erupt” within a short time. Indeed, if the tumor nodule was 1 cm in size 3 months ago and its doubling time is 6 months, it will now be only slightly bigger: 1.5 cm. By contrast, if its doubling time is only 1 month, it will have doubled in size twice within the same short period of time, becoming 6 cm!  (HOW IS IT POSSIBLE? HE/SHE WAS WELL AND NOW THEY SAY THERE’S NOTHING MORE THEY CAN DO)

In short, it may take 10 years for a tumor to become visible if its doubling time is 3 months,  5 years if it is half as long, and 20 years if it is twice as long. 

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