A means of cancer control by which its occurrence can be prevented, slowed down or reversed by the administration of one or more naturally occurring and or synthetic agents.
Involves the use of synthetic or naturally occurring substances to reduce cancer risk among unaffected persons (primary prevention) and individuals with preneoplastic processes (secondary prevention, or to prevent carcinogenesis in people already treated for a primary cancer (tertiary prevention).
Prostate Cancer Prevention Trial (PCPT) showed a 25% relative risk reduction in the incidence of prostate cancer with the use of finasteride in the study that included more than 8000 and then was a randomized placebo control study.
Prostate Cancer Prevention Trial (PCPT) the use of finasteride was associated with a 6.4% diagnosis of high grade prostate cancer as opposed to 5.1% in the placebo arm.
Prostate Cancer Prevention Trial (PCPT) Indicated finasteride reduced the risk of prostate cancer by about one third and high-grade prostate cancer was more common in the treatment group than in the placebo group, but after 18 years therevwas no significant difference in the groups in overall survival, or survival after the diagnosis of prostate cancer (Thompson IM et al).
Dutasteride of Prostate Cancer Events (REDUCE) trial including 7000 men, and reduced prostate cancer incidence by 23% after 4 years of treatment.
The overall reduction in prostate cancer diagnoses in the above two studies resulted from a decreased incidence of only low-grade prostate cancer, Gleason’s score 6 or below, and there was an absolute increase in the incidence of high-grade prostate cancers in the chemoprevention group.
The use of 5a-reductase inhibitors for chemoprevention of prostate cancer was studied in patients who did not have diagnosed prostate cancer but who were at risk.
Five alpha-reductase inhibitors reduce PSA values and any increase in the PSA level above the lowest value obtained may signal the presence of prostate cancer, even if the value remains in normal range for men not taking such an agent.
Randomized trials of beta-carotene, ascorbic acid, alpha tocopherol, selenium, vitamin D and folic acid failed to show evidence of efficacy for cancer prevention