  Cancer prognosis can be regarded as estimating the risk of future outcomes
from multiple variables. In prognostic signatures, these variables represent
expressions of genes that are summed up to calculate a risk score. However, it
is a natural phenomenon in living systems that the whole is more than the sum
of its parts. We hypothesize that the prognostic power of signatures is
fundamentally limited without incorporating emergent effects. Convergent
evidence from a set of unprecedented size (ca. 10,000 signatures) implicates a
maximum prognostic power. We show that a signature can correctly discriminate
patients' prognoses in no more than 80% of the time. Using a simple simulation,
we show that more than 50% of the potentially available information is still
missing at this value.
