A few years ago, I wrote on the growth speed of pheo. Pheo,
contrary to conventional wisdom, grows slowly, at an average speed of one tenth
of an inch (0.2 cm) every year. Recently, a study showed that the biochemical
markers of pheo appear to also rise slowly. This study is interesting in a few
aspects. It was based on the Department of Defense Serum Repository (DoDSR).
The DoDSR is a large serum bank of all members of the US military forces and
boasts of 50 million specimens. The specimens were collected on annual physicals.
The authors used a smart research strategy. They identified people who had ever
served in the US military and been diagnosed with pheo. They then tracked down
the patients’ serum specimens and measured the metanephrine and normetanephrine
levels in the specimens. For example, a person could be enrolled in military
service at age 20 and diagnosed with pheo at age 40. All his serum specimens
since he (most of the subjects were men, as expected) joined the military were
available for testing. The authors actually picked only 3 specimens for testing.
The authors found out that the serum metanephrine or
normetanephrine levels began to be elevated years before diagnosis. For
example, the levels turned abnormal about 6 years before pheo diagnosis and
were 3-fold elevated about 4 years before diagnosis. The average time of
doubling of the marker levels was about 3 years. Individual patients had very
wide differences in the rise of marker levels. For example, some patients had a
doubling time less than 1 and half years, while some others had a doubling time
more than 8 years. The authors thus concluded that a steady and slow rise of
pheo marker levels is very suggestive of pheo. Because there were no imaging
data, we don’t know if the rise of pheo marker levels is related to tumor
growth, which is a limit of the study. Other studies do show parallel increase
in pheo marker levels and tumor burden AFTER diagnosis.
Dr. Pheo
