Why weren’t these metastases discovered sooner, so that treatment could have started sooner? This question is frequently asked in these conditions. The answer is that they were too small to see (less than 0.5 – 1 cm). FIGURES 2 and 3
In the first case, the staging result is truly negative because the primary tumor has not spread outside the local site of origin as evidenced by negative CT, PET scan and magnetic resonance tests (=no tumor in other organs). After the primary tumor is removed, the patient is cured.
In the second case, the staging result is falsely negative because although the CT, PET scan and magnetic resonance tests are negative (=no tumor in other organs) the primary tumor has already spread outside the local origin, but these small nodules are too small to be revealed by the imaging tests. These tests usually disclose nodules of at least 0.5-1 cm (the dotted line in the figure). After the primary tumor is removed, the patient is not cured. A relapse will become known when these small nodules have grown above that threshold.
In the third case, the staging result is positive (=presence of cancer in other organs) because metastases are already seen by the staging tests: they are already large enough at the time the primary cancer is discovered.
Imaging tests, such as CT and PET, have their limits, and they are unable to detect such small metastases.
One small consolation is that the consequences of this delay are unimportant in any case. Indeed:
- Nothing would change if the metastases were discovered 3 or 6 months earlier; as the treatment generally has the same probability of working partially (temporarily reducing metastases’ size) whether they are only 0.5-1 cm or whether they are already 3-4 cm.
- In the advanced phase, treatment is unfortunately unable to eliminate metastases, whether they are already 3-4 cm or very small (0.5-1 cm).
There seems to be a contradiction between the idea that metastases are incurable even when very small (less than 1 cm, still invisible) and what we said about preventive adjuvant therapy, which is administered in order to “eliminate micrometastases” after surgery on the primary tumor. (ADJUVANT THERAPY). To explain this apparent contradiction, we need to point out that there is a big difference between micrometastases (much smaller than 1 mm) and metastases already 5-10 mm in size, though still too small to be seen. The difference in size between these two conditions is of 100-1000 times.