Friday, July 1, 2016

Biochemical growth speed of pheo

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