Here is a description of SP and it benifits. It does not say anything about causing cancer and in my research I have not found any info that claims otherwise. I used SP for about 6 months and it did help some with the hirsutism but it made my face and skin so oily and broken out that I had to stop using it. Hope this has helped you.
Supplement: Saw Palmetto
Description: Saw palmetto is a dwarf palm tree found in the United States from the Carolinas to Texas. For centuries, the crude extracts of saw palmetto have been used to improve sperm production and to increase breast size and sexual vigor, but its most effective and only scientifically based use is to improve symptoms of benign prostatic hyperplasia (BPH).
Claims: Aids in the treatment of Benign Prostatic Hyperplasia (BPH)
Increases libido
Increase in sperm production
Increase in breast size of women
Useful as a urinary antiseptic and diuretic
Prevents hair loss
Theory: The premise for using Saw Palmetto is that it maintains normal prostate health by decreasing the metabolism and action of male steroids. Saw Palmetto has been demonstrated to decrease the activity of 5-alpha reductase which stimulates the conversion of testosterone to dihydrotestosterone (DHT), its more active form. Since DHT is necessary for excessive growth (hyperplasia) of the prostate and is elevated in men with BPH, inhibition of 5-alpha reductase, and therefore DHT production, may alleviate BPH and the associated compression of the urethra (the tube that runs through the prostate gland to carry urine from the bladder). Additionally, studies have shown that Saw Palmetto helps to inhibit the production of various inflammatory factors, thus serving to decrease overall prostate inflammation. The prescription medication for treating BPH, finasteride is available as Proscar for BPH and a lower potency version called Propecia for treating hair loss in men (because the same conversion of testosterone to DHT is thought to result in thinning and loss of hair in men).
Scientific Support: In one rather large study using over 1000 patients enrolled over the age of 50, Saw Palmetto was found to be equally as effective as finasteride (Proscar) for the treatment of BPH. In a 12-week study of 1334 patients on the Saw Palmetto extract, Talso, over 80% of patients reported good to excellent results. Another study of 40 BPH patients over a 60-day period showed 25% of patients to have "good" results and 75% had "excellent" results with respect to BPH severity and symptoms. In a double-blind study of 27 patients, Saw Palmetto resulted in positive benefits in 43% of people receiving the extract, versus only 15% of subjects in the placebo group. Several recent case reports and small clinical trials have shown a particular combination of saw palmetto and Chinese herbs called “PC-SPES” (chrysanthemum, dyers woad, licorice, reishi, san-qi ginseng, rabdosia, saw palmetto, and baikal skullcap) to be effective in alleviating symptoms of BPH and even in reducing blood levels of prostate-specific antigen (PSA), a marker for prostate cancer. Several other smaller studies have shown significant improvements in symptoms of BPH such as improvements in maximum urinary flow rates, reduced trips to the bathroom, a greater ability to fully empty the bladder and an increased quality of life.
Safety: Headaches and gastrointestinal disturbances including diarrhea and nausea have been reported, although these adverse effects are rare. Because Saw Palmetto has primarily been tested in adult males, it is not recommended for children, or for women who are pregnant or lactating. No drug interactions have been reported for Saw Palmetto. It is important to note that Saw Palmetto extract may only treat the symptoms of BPH, and therefore those with an enlarged prostate should consult with their physician on a regular basis.
Value: A one-month supply of Saw Palmetto extract is approximately $15-$30. Considering the possible health benefits (similar to the prescription drug, Proscar for BPH and Propecia for hair loss) and the fact that Saw Palmetto appears to be safe and effective in several scientific studies, the value of taking Saw Palmetto seems considerable.
Dosage: About 160mg of the oil-based ("lipophilic") berry extract should be taken twice a day (morning and evening) for at least 30 days (total daily dose of approximately 320mg). Look for a brand that standardizes it’s extract based on fatty acid and sterol content – about 80-90% total fatty acids and sterols is recommended.
Saw Palmetto Long-term Use 
