Historical perspective of tumor growth kinetics exponential and Gompertzian kinetics

Though there is occasional homage paid to Gompertzian tumor growth, for practical purposes, when we care for patients, tumors are frequently undergoing exponential expansion.

In the absence of tumor mutation or perturbation by therapy the growth rate of exponentially growing tumors is constant. Rarely, there may be periods of interrupted growth.

Gompertzian growth [1, 2, 3] is best described by a sigmoid-shaped curve. At tumor initiation growth is occult, slow and remains subclinical for several years. A second phase is the rapid, clinically apparent exponential phase lasting for a few years followed by the slower terminal growth phase as the tumor approaches 35-40 doublings representing a volume approaching 1000 cc or a tumor diameter of 10 cm Figure 1. The duration of tumor growth from inception is several years and for three quarters of that period the tumor is clinically undetectable. At the time of discovery, the oncologist is attending to the last quarter of tumor growth.

Figure 1. Note the differences between the exponential and Gompertzian growth curves. The lethal burden of tumor is approximately 1000 cc or ~35-40 doublings. In the clinic when tumors reach 0.5-1 cm in diameter (30 doublings or 109 cells) they are measurable and follow the exponential growth curve, the steeper the slope the larger the tumor specific growth rate (SGR). Nonetheless, many feel that when looking at the entire lifespan of malignant tumors (over several years) tumor growth may better be described by Gompertzian kinetics [3].

Figure 1. Note the differences between the exponential and Gompertzian growth curves. The lethal burden of tumor is approximately 1000 cc or ~35-40 doublings. In the clinic when tumors reach 0.5-1 cm in diameter (30 doublings or 109 cells) they are measurable and follow the exponential growth curve, the steeper the slope the larger the tumor specific growth rate (SGR). Nonetheless, many feel that when looking at the entire lifespan of malignant tumors (over several years) tumor growth may better be described by Gompertzian kinetics [3].

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