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Screening minskade inte dödlighet i prostatacancer i amerikansk studie

17 januari 2012.

DM: Män som screenades med PSA-test och palpation av prostatan dog lika ofta i prostatacancer som andra män, i en stor studie.

Många män gör i dag ett test för PSA, prostataspecifikt antigen, för att tidigt upptäcka prostatacancer. Men frågan om generell screening är en het fråga, med både förespråkare och skeptiker.

I en nyligen publicerad amerikansk studie såg forskare ingen minskad dödlighet i prostatacancer hos män som screenats med PSA-test och palpation av prostatakörteln via ändtarmen, jämfört med män som inte undersökts på detta vis.

Forskare följde närmare 77 000 män i åldern 55-74 år i upp till 13 år. Ungefär hälften av dem lottades till screening med PSA-test årligen under sex år samt med årlig palpation av prostatakörteln via ändtarmen i fyra år. Övriga män fungerade som kontrollgrupp.

Drygt hälften av deltagarna i studien följdes i 13 år. 

Vid uppföljningstidens slut var dödligheten i prostatacancer ungefär densamma i de båda grupperna. Det är i linje med resultat som rapporterats tidigare under studien. Dagens Medicin har tidigare skrivit om resultaten, se artikel här intill.

Studieförfattarna spekulerar i flera orsaker till resultaten. Bland annat genomgick många deltagare i kontrollgruppen PSA-tester under uppföljningstiden. Många hade också gjort tester innan de inkluderades i studien.

Forskarna skriver att de efter 13 års uppföljning inte funnit några bevis för att organiserad årlig screening medför någon överlevnadsfördel, jämfört med så kallad opportunistisk screening i en väl definierad högriskgrupp.

Bakom studien, som publiceras i tidskriften Journal of the National Cancer Institute, står bland andra forskare vid Washington University i Missouri, USA.

 

Abstract

Background The prostate component of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial was undertaken to determine whether there is a reduction in prostate cancer mortality from screening using serum prostate-specific antigen (PSA) testing and digital rectal examination (DRE). Mortality after 7–10 years of follow-up has been reported previously. We report extended follow-up to 13 years after the trial.

Methods A total of 76 685 men, aged 55–74 years, were enrolled at 10 screening centers between November 1993 and July 2001 and randomly assigned to the intervention (organized screening of annual PSA testing for 6 years and annual DRE for 4 years; 38 340 men) and control (usual care, which sometimes included opportunistic screening; 38 345 men) arms. Screening was completed in October 2006. All incident prostate cancers and deaths from prostate cancer through 13 years of follow-up or through December 31, 2009, were ascertained. Relative risks (RRs) were estimated as the ratio of observed rates in the intervention and control arms, and 95% confidence intervals (CIs) were calculated assuming a Poisson distribution for the number of events. Poisson regression modeling was used to examine the interactions with respect to prostate cancer mortality between trial arm and age, comorbidity status, and pretrial PSA testing. All statistical tests were two-sided.

Results Approximately 92% of the study participants were followed to 10 years and 57% to 13 years. At 13 years, 4250 participants had been diagnosed with prostate cancer in the intervention arm compared with 3815 in the control arm. Cumulative incidence rates for prostate cancer in the intervention and control arms were 108.4 and 97.1 per 10 000 person-years, respectively, resulting in a relative increase of 12% in the intervention arm (RR = 1.12, 95% CI = 1.07 to 1.17). After 13 years of follow-up, the cumulative mortality rates from prostate cancer in the intervention and control arms were 3.7 and 3.4 deaths per 10 000 person-years, respectively, resulting in a non-statistically significant difference between the two arms (RR = 1.09, 95% CI = 0.87 to 1.36). No statistically significant interactions with respect to prostate cancer mortality were observed between trial arm and age (Pinteraction = .81), pretrial PSA testing (Pinteraction = .52), and comorbidity (Pinteraction = .68).

Conclusions After 13 years of follow-up, there was no evidence of a mortality benefit for organized annual screening in the PLCO trial compared with opportunistic screening, which forms part of usual care, and there was no apparent interaction with age, baseline comorbidity, or pretrial PSA testing.

 

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