Another important aspect of screening tests is that:
1 - the cancer tested for has to be common
2 - It has to have a high positive predictive value, , ie it has to detect much more positive cases than negative cases (as opposed to negative predictive value, which tells us how many false positive cases a test can give). This is important because if they PPV is low or the NPV is high, it means a big number of healthy people will undergo further tests and maybe expensive treatments unnecessarily.
3 - it has to be cost effective
4 - the cost of prevention of the disease being tested for should be overall lower than the cost of the treatment of this disease.
For example, recently the necessity of screening for lung cancer has been debated but it was not found to be feasible.
Of course as Dr. Irani has advised: healthy living is key in cancer (and many other diseases) prevention.