R2.2: Tumour Cell Kinetics

The growth of a cancer is dependent on several factors:

• The time it takes for a cell to duplicate itself (the cell cycle time Tc)
• The percentage of cells within the tumour that are growing (the growth fraction GF)
• The number of cells from the tumour that are lost, either through cell death or senescence (the cell loss factor)

The potential doubling time Tpot of a tumour is the time it would take for a tumour to double in size, assuming that no cells are lost. It is found by:

(1)
\begin{align} T_{pot}=\frac{T_c}{GF} \end{align}

The volume doubling time VDT is the observed time a tumour takes to double in size.

The cell loss factor CLF relates the potential doubling time to the volume doubling time, and is found by:

(2)
$$CLF=1-{T_{pot}}{VDT}$$

The CLF for many tumours is over 80-90% once they have reached a significant size.

## Factors influencing tumour kinetics

Tumours are thought to grow rapidly at first due to a low cell loss factor - the tumour is small enough that poor vascular supply and central necrosis are less of a problem. A tumour cell must undergo thirty divisions to form a clinically detectable mass.