They tell you if a given treatment is effective. The tumor marker
must decline or at least be stabilized if the treatment is consi-
dered effective.
An exception to this rule is the phenomenon SURGE. If this
phenomenon occurs, the tumor marker will increase instead of
decreasing in spite of the fact that the tumor gets smaller. This
is presumably due to dead cancer cells emerging in the patient’s
blood giving rise to brief SURGE.
In rare cases it has, however, been seen that a SURGE can last
for 3 months, before the tumor marker starts to fall.
The tumor marker will often be normal after the primary tumor
has been treated by surgery, radiation or chemotherapy. If it
begins to grow at that particular time, it is usually an early
signal that the tumor has started growing again. The increase
in the tumor marker might arise many months before you can
find cancer cells in the body. Even increases within the normal
area generally mean that the cancer has started growing again.
