Sir,
The prevalence of cancers increases in end-stage renal disease (ESRD) patients [1]. Prostate-specific antigen (PSA) is a useful serum marker for prostate cancer, one of the most common malignant neoplasmas; the levels are often elevated in ESRD [2], which is likely to be associated with an increased prevalence of prostate cancer [1]. Diabetes mellitus (DM) (mostly type 2) is the major cause of ESRD; however, in accordance with low serum PSA levels in DM patients [3], the risk of prostate cancer is decreased in DM patients [4], while that of other cancers is increased [5]. How are the PSA levels and prostate cancer prevalence of ESRD patients caused by DM?
To address this issue, we chose subjects of ESRD caused by DM or chronic glomerulonephritis (CGN) (as a control) receiving haemodialysis, and measured their serum PSA concentrations. The mean age, a risk factor of prostate cancer, was no different between the two groups (Table 1). The haemodialysis duration was twice as long in the CGN group (Table 1), but was unrelated to PSA levels in both groups when examined by Spearman's correlation coefficient obtained using the rank test. The PSA levels were significantly lower in the DM group compared to those in the CGN group (Table 1). This is in agreement with previous results showing that the PSA levels of DM patients were low in subjects without ESRD [4]. The PSA levels of the DM or CGN group were similar to those of healthy volunteers (1.63 ± 0.13 ng/ml) and ESRD patients (2.18 ± 0.12 ng/ml), respectively [2]. This indicates that PSA levels of ESRD DM patients are slightly lower than those of healthy volunteers, and that the PSA levels of CGN are representatives for the ESRD population. The prevalence of prostate cancer was not significantly different between the two groups, yet there is a tendency for a decreased number of patients with PSA values >4 ng/ml in the DM group, in comparison with the CGN group (Table 1). The levels of testosterone associated with increased prostate cancer risk, and those of insulin that promotes prostate cancer cell growth, are lower in DM patients [5]; these factors remain at lower levels after the patients advance to ESRD, which may explain low PSA levels in the DM group.
Table 1.
Parameter comparison in patients with ESRD caused by DM or CGN
| DM | CGN | |
|---|---|---|
| Number of patients | 332 | 549 |
| Age (years)a | 65.66 ± 0.50# | 64.10 ± 0.43 |
| Haemodialysis duration (years)b | 5.97 ± 0.22* | 11.87 ± 0.34 |
| Serum PSA (ng/ml)c | 1.53 ± 0.20* | 2.09 ± 0.22 |
| Number of patients with PSA >4 ng/mld | 19 (5.9%)** | 47 (8.9%) |
| Number of patients undergone | ||
| prostate biopsye | 6# | 14 |
| Number of prostate | ||
| cancer-detected patientsf | 3# | 9 |
Values were the means ± SE. *P ≤ 0.05. ** P ≤ 0.1. # not significant.
at-test, b,cKruskal–Wallis test and d,e,fchi-square test were used.
Our results suggest that DM is associated with decreased PSA levels, and likely of prostate cancer risk, irrespective of the complication of ESRD. These results support an inverse relationship between DM and prostate cancer.
Conflict of interest statement. None declared.
References
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