From exponential start to Gompertzian slowdown
Early in its life a tumor tends to grow exponentially: every cell can divide, so the population doubles at a roughly constant rate and the curve climbs steeply. But this cannot continue indefinitely. As the tumor enlarges, an increasing share of cells run short of oxygen and nutrients, sit far from blood vessels, or stop dividing, so the growth rate falls even as absolute size keeps rising.
This deceleration is well described by a Gompertzian curve, which rises fast then bends toward a plateau as the tumor approaches the limits its host environment can support. By the time many tumors are detectable, they are already in the slowing phase, which has implications for how growth appears over the period of clinical observation.
Why the curve shape matters for treatment
The fraction of cells actively dividing changes along the curve, and many therapies hit dividing cells hardest. A large, slow-growing tumor may have a smaller proportion of vulnerable dividing cells than a small fast one. Models of growth kinetics inform thinking about dose timing, though real tumors are heterogeneous and deviate from any clean curve.
Comparing the growth phases
This is general educational information about cancer biology, not medical advice. Growth curves are idealized models; individual tumor behavior and treatment are assessed by clinicians.