Rise in prostate-specific antigen in men with untreated low-grade prostate cancer is slower during spring-summer.
To test the hypothesis that the rate of rise in prostate-specific antigen (PSA) is slower during the spring-summer than during the rest of the year, we used PSA data from a prospective single-arm cohort study of men who had been followed to characterize a watchful observation protocol with selective delayed intervention for clinically localized, low-to-intermediate grade prostate adenocarcinoma. The rate of PSA increase was calculated as the visit-to-visit slope of log (PSA) against time, from 1 calendar-quarter visit to the next. The nonparametric Friedman test confirmed differences in rate of PSA rise among the calendar quarters (P = 0.041). Post hoc analysis showed the rate of PSA increase during Q2 was significantly slower than in each one of the other calendar quarters (Q1 versus Q2, P = 0.025; Q3 versus Q2, P = 0.002; Q4 versus Q2, P = 0.013), with no differences among quarters Q1, Q3, and Q4. These results are consistent with the vitamin D hypothesis that the higher 25-hydroxyvitamin D levels associated with spring and summer have a desirable effect on prostate biology. The therapeutic implication is that vitamin D supplementation in the range of 2000 IU/d, a dose comparable to the effect of summer, can benefit men monitored for rising PSA.
Vieth
R
R
Mount Sinai Hospital, Toronto-Sunnybrook Regional Cancer Center, Sunnybrook and Women's College Health Sciences Centre, University of Toronto, Toronto, Canada. rvieth@mtsinai.on.ca
Choo
R
R
Deboer
L
L
Danjoux
C
C
Morton
G C
GC
Klotz
L
L
D000230:Adenocarcinoma / Q000097:blood* / Q000601:surgery; D000368:Aged; D000369:Aged, 80 and over; D002112:Calcifediol / Q000097:blood; D015331:Cohort Studies; D018450:Disease Progression; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000601:surgery; D012621:Seasons; D020728:Transurethral Resection of Prostate; D014466:Ultraviolet Rays; D014517:Ureteral Obstruction / Q000150:complications; D014807:Vitamin D / Q000502:physiology
D014807:Vitamin D; D017430:Prostate-Specific Antigen; D002112:Calcifediol