PSA doubling time is not the same as tumour cells growth doubling time. The former is just one of the many PCa markers and the latter is the actual timeline for the cancer cells to double itself forming the tumour mass. Whilst PSA doubling time does indicate cancer growth, it is the unsually high level of PSA that is the main concern and it should initiate other clinical tests to confirm resurgence of the cancer cells. Slow PSA doubling time together with slow velocity in increaseing PSA are fairly safe until the values past biochemical recurrence at 0.02 ng/L after radical prostatectomy and at 2.0 ng/L plus nadir point for radiation therapy.
Cancer cells growth go through three steps of development, with different timelines for agressive cells and slower growing cancer cells. The growth steps are Initiation, Promotion and Progression. Below is an extract from the Canadian Cancer Society describing the growth timeline of cancer cells doubling itself to form the tumour.
Progression
The change (transformation) in a normal cell causes it to behave, grow and function quite differently and turn into a cancer cell. The cell’s growth instructions get mixed up. This causes the cell to go on growing and reproducing itself. The time it takes a cell to double in number is called the doubling time. A fast-growing cancer cell may double over 1–4 weeks, a slower growing one over 2–6 months. The doubling time varies with the type of cancer cell and how aggressive it is.
In adults, there is usually a long developmental (latency) period after initiation during which promotion and progression are occurring, which means it takes a long time before a cell becomes cancerous. In children, this latency period is much shorter.
As cancer cells grow, they can group together to form a lump (tumour). It can take several months or even years (up to 30 years) for cancer cells to form a lump that is big enough to be felt or detected by an imaging test. By this time, the cancer cell has undergone about 30 or more doublings, and even though the lump is very small, it can contain about a billion cells. In children, the time is much less for a lump to become noticeable.
I am still trying to find the study showing the direct corelation between PSA doubling time and cancer cells growth doubling time.
Take care
Allen Lai
