Why is likelihood of prostate cancer diagnosis declining?


In an article discussed earlier this week on this web site (click here for more), Howard argued that the USPSTF recommendation to abandon PSA screening in men of ≥ 75 years of age was a key factor in the decrease in the incidence of prostate cancer in men in this age group. But is Dr. Howard right?

Dr. Howard is an expert in the statistical analysis of the SEER data. We certainly are not. However, we feel it is only appropriate to point out that — according to SEER itself — the incidence of diagnoses of prostate cancer in men ≥ 75 years has declined significantly over the period from 1992 to 2009, and in three distinct phases:

  • From 1992 to 1995, the age-adjusted incidence of prostate cancer dropped like a stone — from a high point of 1,741/100,000 in 1992 to 1,110/100,000 in 1994 and to 993/100,000 in 1995 (a 43 percent decrease over a 4-year period).
  • From 1995 to 2000, the age-adjusted incidence then flat-lined. As we have seen, it was 993/100,000 in 1995 and in 2000 it was exactly 1,000/100,000. To all intents and purposes, there was no significant change in the incidence of prostate cancer in men ≥ 75 years during those 6 years.
  • From 2000 to 2009, the age-adjusted incidence has been falling at a fairly steady rate, from 1,000/100,000 in 2000 to 631/100,000 in 2009 (a 37 percent decrease over 10 years).

Indeed, according to SEER, the decrease in the incidence of prostate cancer in men ≥ 75 years was 22 percent between 2007 (807/100,000) and 2009 (630/100,000).

Similarly, and again according to SEER itself — the incidence of diagnoses of prostate cancer in all men declined significantly over the period from 1992 to 2009, and again in three distinct phases:

  • From 1992 to 1995, the age-adjusted incidence of prostate cancer again dropped like a stone — from a high point of 237/100,000 in 1992 to 180/100,000 in 1994 and to 169/100,000 in 1995 (a 29 percent decrease over a 4-year period).
  • From 1995 to 2000, the age-adjusted incidence then increased gradually in all men — from  169/100,000 in 1995 to 183/100,000 in 2000 (an 8 percent increase over a 6-year period).
  • From 2000 to 2009, the age-adjusted incidence has been falling again at a fairly steady rate, from 183/100,000 in 2000 to 152/100,000 in 2009 (a 17 percent decrease over 10 years).

However, the gradual decrease in the incidence of prostate cancer in all American males over the past 10 years has not been steady. Rather, there has been some noticeable variation (up and down) from year to year.

If you want to look at these data for yourself, just have a look at the two comparative charts immediately below. (You can click on them to see larger versions.)

Age-adjusted prostate cancer incidence (75 and older; all races; 1975-2009)

Age-adjusted prostate cancer incidence (all ages; all races; 1975-2009)

So it is hard to know whether the USPSTF’s recommendation in 2008 really had the impact that Howard is claiming. It is just as justifiable to suggest that the continuing decline in incidence of prostate cancer diagnosis among men of 75 years and older was part of a continuing trend that had started 9 years earlier. We can all speculate about exactly why we have observed such a decline … but attribution of a specific cause to this decline over any 3-year period may be much more difficult to justify.

One Response

  1. PRIOR YEAR DIAGNOSES, ESPECIALLY DURING SURGE, WOULD REDUCE NUMBER OF LATER YEARS DIAGNOSES FOR MEN AGED >= 75

    It is clear that a 55-year-old man diagnosed in 1995, for example, would not be in the group of men diagnosed in 2005 when he would be 75. Thus, the surge from 1992-1995 would have depleted the pool, to an extent. I’m wondering if this factor has been analyzed.

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