The question of whether the use of 5α-reductase inhibitors (5-ARIs) like finasteride (Proscar) and dutasteride (Avodart) is really associated with a significantly increased risk for diagnosis of high-risk and/or lethal prostate cancers remains unanswered. However, yet another set of data from the Health Professionals Follow-up Study (HPFS) has offered us some additional insights.
As The “New” Prostate Cancer InfoLink has observed on a number of prior occasions, if the use of 5-ARIs really is associated with a significant increase in the likelihood of a diagnosis of high-risk and/or lethal prostate cancers, then wouldn’t this risk be apparent among the tens of thousands of men who have been getting treatment (often for years) with 5-ARIs for benign prostatic hyperplasia (BPH) — the very common enlargement of the prostate that occurs with increasing age?
The HPFS research team (see Preston et al.) therefore looked at their data on 38,058 men who had been followed from 1996 to 2010, and specifically at data from those men who had been diagnosed with prostate cancer during that timeframe and the use of 5-ARIs by these men during that same timeframe.
Here is what they found:
- 3,681 cases of incident prostate cancer were identified among 448,803 person-years of follow-up.
- 289 cases were “lethal” (i.e., metastatic disease or actual death from prostate cancer).
- 456 cases were high grade (i.e., a Gleason score of 8 to 10 at diagnosis).
- 1,238 were intermediate grade (i.e., a Gleason score of 7).
- 1,600 were low grade (i.e., a Gleason score of 2 to 6).
- 2,878/38,058 men (7.6 percent) said they had used a 5-ARI between 1996 and 2010.
- After making appropriate adjustments for things like age, PSA testing, and other confounding factors, it was shown that, during the study period, compared to non-users of 5-ARIs who were diagnosed with prostate cancer,
- 5-ARI users had a significantly lower overall risk for diagnosis of prostate cancer (hazard ratio [HR] = 0.77).
- 5-ARI users had a significantly lower risk for diagnosis with Gleason 7 disease (HR = 0.67).
- 5-ARI users had a significantly lower risk for diagnosis with low-grade (i.e., Gleason 2 to 6) prostate cancer (HR = 0.74)
- 5-ARI users had a comparable risk for diagnosis with high-grade (i.e., Gleason 8 to 10) prostate cancer (HR = 0.97)
- 5-ARI users had a comparable risk for diagnosis with lethal prostate cancer (HR = 0.99).
- Increased duration of use of 5-ARIs was associated with
- A lower overall risk for diagnosis of prostate cancer (HR for 1 year of additional use =0.95)
- A lower overall risk for diagnosis of localized prostate cancer (HR for 1 year of additional use =0.95)
- A lower overall risk for diagnosis of low-grade (i.e., Gleason 2 to 6) prostate cancer (HR for 1 year of additional use =0.92)
- No increase in risk for lethal, high-grade, or Gleason 7 prostate cancer.
The authors conclude that:
While 5-ARI use was not associated with developing high-grade or lethal prostate cancer, it was associated with a reduction in low-grade, GS 7, and overall prostate cancer.
However, they appropriately note also that
Because the number of patients with high-grade or lethal prostate cancer in our cohort was limited, we cannot rule out potential risk of harm with 5-ARI use.
While these data can not be used to make an absolute statement that there is no association between the use of 5-ARIs and risk for high-grade or lethal prostate cancers, they do add to the data suggesting that such risk, if it does exist, is extremely small.
What would, of course, be extremely helpful would be an analysis by the HPFS research team of all men in their database who took 5-ARIs during the study period and the occurrence of prostate cancer among this cohort, compared to the occurrence of prostate cancer in those who did not take a 5-ARI. Whether funding exists to examine that question, we do not know.