CONTEXT AND OBJECTIVE:: The purpose of screening tests for cancer is to detect it at an early stage in order to increase the chances of treatment. However, their unrestrained use may lead to unnecessary examinations, overdiagnosis and higher costs. It is thus necessary to evaluate their clinical effects in terms of benefits and harm.
DESIGN AND SETTING:: Review of Cochrane systematic reviews, carried out in the Discipline of Evidence-Based Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo.
METHODS:: Cochrane reviews on the clinical effectiveness of cancer screening procedures were included. Study titles and abstracts were independently assessed by two authors. Conflicts were resolved by another two authors. Findings were summarized and discussed.
RESULTS:: Seventeen reviews were selected: fifteen on screening for specific cancers (bladder, breast, colorectal, hepatic, lung, nasopharyngeal, esophageal, oral, prostate, testicular and uterine) and two others on cancer in general. The quality of evidence of the findings varied among the reviews. Only two reviews resulted in high-quality evidence: screening using low-dose computed tomography scans for high-risk individuals seems to reduce lung cancer mortality; and screening using flexible sigmoidoscopy and fecal occult blood tests seems to reduce colorectal cancer mortality.
CONCLUSION:: The evidence found through Cochrane reviews did not support most of the commonly used screening tests for cancer. It is recommended that patients should be informed of the possibilities of false positives and false negatives before they undergo the tests. Further studies to fully assess the effectiveness of cancer screening tests and adverse outcomes are required.
Prostate cancer (PC) is the most commonly diagnosed non-cutaneous cancer in men and their second or third leading cause of cancer death. Prostate-specific antigen (PSA) testing for PC has been in common practice for more than 20 years.
OBJECTIVES:
A systematic review of the scientific literature was conducted to determine the effectiveness of PSA-based population screening programs for PC to inform policy decisions in a publicly funded health care system.
DATA SOURCES:
A systematic review of bibliographic databases was performed for systematic reviews or randomized controlled trials (RCT) of PSA-based population screening programs for PC.
REVIEW METHODS:
A broad search strategy was employed to identify studies reporting on key outcomes of PC mortality and all-cause mortality.
RESULTS:
The search identified 5 systematic reviews and 6 RCTs. None of the systematic reviews found a statistically significant reduction in relative risk (RR) of PC mortality or overall mortality with PSA-based screening. PC mortality reductions were found to vary by country, by screening program, and by age of men at study entry. The European Randomized Study of Screening for Prostate Cancer found a statistically significant reduction in RR in PC mortality at 11-year follow-up (0.79; 95% CI, 0.67-0.92), although the absolute risk reduction was small (1.0/10,000 person-years). However, the primary treatment for PCs differed significantly between countries and between trial arms. The American Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) found a statistically non-significant increase in RR for PC mortality with 13-year follow-up (1.09; 95% CI, 0.87-1.36). The degree of opportunistic screening in the control arm of the PLCO trial, however, was high. None of the RCTs found a reduction in all-cause mortality and all found a statistically significant increase in the detection of mainly low-risk, organ-confined PCs in the screening arm.
CONCLUSIONS:
There was no evidence of a PC mortality reduction in the American PLCO trial, which investigated a screening program in a setting where opportunistic screening was already common practice. Given that opportunistic PSA screening practices in Canada are similar, it is unlikely that the introduction of a formal PSA screening program would reduce PC mortality.
BACKGROUND: Diversi test di screening popolari, come la mammografia e l'antigene prostatico specifico, si sono incontrati con ampia polemiche e / o hanno perso la loro approvazione di recente. Abbiamo sistematicamente valutato evidenza da studi randomizzati e controllati (RCT) sul fatto che lo screening riduce la mortalità a causa di malattie in cui la morte è un risultato comune.
METODI: Abbiamo cercato tre fonti: Stati Uniti Preventive Services Task Force (USPSTF), Cochrane Database of Systematic Reviews, e PubMed. Abbiamo estratto stato raccomandazione, la categoria delle prove e la disponibilità RCT sulla mortalità per i test di screening per le malattie su adulti asintomatici (esclusi donne incinte e bambini) da USPSTF. Abbiamo identificato meta-analisi e RCT individuali sullo screening e la mortalità per Cochrane e PubMed.
RISULTATI: Abbiamo selezionato 19 malattie (39 test) su 50 malattie / disturbi per i quali USPSTF prevede la valutazione di screening. Screening è raccomandato per 6 malattie (12 test) dei 19. Abbiamo valutato 9 non sovrapposti metanalisi e 48 prove individuali per questi 19 malattie. Tra i risultati della meta-analisi, riduzioni dove gli intervalli di confidenza al 95% (IC) esclusi il nulla si è verificato per quattro stime di mortalità per malattie specifiche (ecografia per aneurisma dell'aorta addominale negli uomini, la mammografia per il cancro al seno, sangue occulto nelle feci e flessibile sigmoidoscopia per il cancro del colon-retto) e per nessuna delle stime di mortalità per tutte le cause. Tra i singoli RCT, riduzioni della mortalità dovuta ai tumori e per tutte le cause in cui gli IC 95% escluso l'nulla si è verificato nel 30% e 11% delle stime, rispettivamente.
In conclusione, tra attualmente disponibili test di screening per le malattie in cui la morte è un risultato comune, riduzioni della mortalità dovuta ai tumori sono rari e le riduzioni in tutte le cause di mortalità sono molto rare o inesistenti.
: The purpose of screening tests for cancer is to detect it at an early stage in order to increase the chances of treatment. However, their unrestrained use may lead to unnecessary examinations, overdiagnosis and higher costs. It is thus necessary to evaluate their clinical effects in terms of benefits and harm.
DESIGN AND SETTING:
: Review of Cochrane systematic reviews, carried out in the Discipline of Evidence-Based Medicine, Escola Paulista de Medicina, Universidade Federal de São Paulo.
METHODS:
: Cochrane reviews on the clinical effectiveness of cancer screening procedures were included. Study titles and abstracts were independently assessed by two authors. Conflicts were resolved by another two authors. Findings were summarized and discussed.
RESULTS:
: Seventeen reviews were selected: fifteen on screening for specific cancers (bladder, breast, colorectal, hepatic, lung, nasopharyngeal, esophageal, oral, prostate, testicular and uterine) and two others on cancer in general. The quality of evidence of the findings varied among the reviews. Only two reviews resulted in high-quality evidence: screening using low-dose computed tomography scans for high-risk individuals seems to reduce lung cancer mortality; and screening using flexible sigmoidoscopy and fecal occult blood tests seems to reduce colorectal cancer mortality.
CONCLUSION:
: The evidence found through Cochrane reviews did not support most of the commonly used screening tests for cancer. It is recommended that patients should be informed of the possibilities of false positives and false negatives before they undergo the tests. Further studies to fully assess the effectiveness of cancer screening tests and adverse outcomes are required.
