Thursday, April 30, 2015

Prostrate Cancer Relative Survival Rate - SEER 1975 -2012 report released 2015

It is most encouraging to note that relative survival past 15 years since 1996 till today are all 90 plus percentage.

Definition of relative survival by SEER

Relative survival is a net survival measure representing cancer survival in the absence of other causes of death. Relative survival is defined as the ratio of the proportion of observed survivors in a cohort of cancer patients to the proportion of expected survivors in a comparable set of cancer free individuals. The formulation is based on the assumption of independent competing causes of death. The relative survival adjusts for the general survival of the U.S. population for that race, sex, age, and date at which the age was coded. If age, race, sex, or year information is missing, that individual is excluded from the analysis.


Allen Lai

Tuesday, April 28, 2015

Cancer cells development

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.

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