Screening for cancer: are resources being used wisely?

Screening programmes for the early detection and prevention of oral cancer

BACKGROUND

Oral cancer is an important global healthcare problem, its incidence is increasing and late-stage presentation is common. Screening programmes have been introduced for a number of major cancers and have proved effective in their early detection. Given the high morbidity and mortality rates associated with oral cancer, there is a need to determine the effectiveness of a screening programme for this disease, either as a targeted, opportunistic or population-based measure. Evidence exists from modelled data that a visual oral examination of high-risk individuals may be a cost-effective screening strategy and the development and use of adjunctive aids and biomarkers is becoming increasingly common.

OBJECTIVES

To assess the effectiveness of current screening methods in decreasing oral cancer mortality.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Oral Health Group's Trials Register (to 22 July 2013), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 6), MEDLINE via OVID (1946 to 22 July 2013), EMBASE via OVID (1980 to 22 July 2013) and CANCERLIT via PubMed (1950 to 22 July 2013). There were no restrictions on language in the search of the electronic databases.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of screening for oral cancer or potentially malignant disorders using visual examination, toluidine blue, fluorescence imaging or brush biopsy.

DATA COLLECTION AND ANALYSIS

Two review authors screened the results of the searches against inclusion criteria, extracted data and assessed risk of bias independently and in duplicate. We used mean differences (MDs) and 95% confidence intervals (CIs) for continuous data and risk ratios (RRs) with 95% CIs for dichotomous data. Meta-analyses would have been undertaken using a random-effects model if the number of studies had exceeded a minimum of three. Study authors were contacted where possible and where deemed necessary for missing information.

MAIN RESULTS

A total of 3239 citations were identified through the searches. Only one RCT, with 15-year follow-up met the inclusion criteria (n = 13 clusters: 191,873 participants). There was no statistically significant difference in the oral cancer mortality rates for the screened group (15.4/100,000 person-years) and the control group (17.1/100,000 person-years), with a RR of 0.88 (95% CI 0.69 to 1.12). A 24% reduction in mortality was reported between the screening group (30/100,000 person-years) and the control group (39.0/100,000) for high-risk individuals who used tobacco or alcohol or both, which was statistically significant (RR 0.76; 95% CI 0.60 to 0.97). No statistically significant differences were found for incidence rates. A statistically significant reduction in the number of individuals diagnosed with stage III or worse oral cancer was found for those in the screening group (RR 0.81; 95% CI 0.70 to 0.93). No harms were reported. The study was assessed as at high risk of bias.

AUTHORS' CONCLUSIONS

There is evidence that a visual examination as part of a population-based screening programme reduces the mortality rate of oral cancer in high-risk individuals. In addition, there is a stage shift and improvement in survival rates across the population as a whole. However, the evidence is limited to one study, which has a high risk of bias and did not account for the effect of cluster randomisation in the analysis. There was no evidence to support the use of adjunctive technologies like toluidine blue, brush biopsy or fluorescence imaging as a screening tool to reduce oral cancer mortality. Further RCTs are recommended to assess the efficacy and cost-effectiveness of a visual examination as part of a population-based screening programme in low, middle and high-income countries.

Screening programmes for the early detection and prevention of oral cancer

BACKGROUND

Oral cancer is an important global healthcare problem, its incidence is increasing and late-stage presentation is common. Screening programmes have been introduced for a number of major cancers and have proved effective in their early detection. Given the high morbidity and mortality rates associated with oral cancer, there is a need to determine the effectiveness of a screening programme for this disease, either as a targeted, opportunistic or population based measure. Evidence exists from modelled data that a visual oral examination of high-risk individuals may be a cost-effective screening strategy and the development and use of adjunctive aids and biomarkers is becoming increasingly common.

OBJECTIVES

To assess the effectiveness of current screening methods in decreasing oral cancer mortality.

SEARCH STRATEGY

The following electronic databases were searched: the Cochrane Oral Health Group Trials Register (to 20 May 2010), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, Issue 2), MEDLINE via OVID (1950 to 20 May 2010), EMBASE via OVID (1980 to 20 May 2010) and CANCERLIT via PubMed (1950 to 20 May 2010). There were no restrictions regarding language or date of publication.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of screening for oral cancer or potentially malignant disorders using visual examination, toluidine blue, fluorescence imaging or brush biopsy.

DATA COLLECTION AND ANALYSIS

The original review identified 1389 citations and this update identified an additional 330 studies, highlighting 1719 studies for consideration. Only one study met the inclusion criteria and validity assessment, data extraction and statistics evaluation were undertaken by six independent review authors.

MAIN RESULTS

One 9-year RCT has been included (n = 13 clusters: 191,873 participants). There was no statistically significant difference in the age-standardised oral cancer mortality rates for the screened group (16.4/100,000 person-years) and the control group (20.7/100,000 person-years). A 43% reduction in mortality was reported between the intervention cohort (29.9/100,000 person-years) and the control arm (45.4/100,000) for high-risk individuals who used tobacco or alcohol or both, which was statistically significant. However, this study had a number of methodological weaknesses and the associated risk of bias was high.

AUTHORS' CONCLUSIONS

Although there is evidence that a visual examination as part of a population based screening programme reduced the mortality rate of oral cancer in high-risk individuals, whilst producing a stage shift and improvement in survival rates across the population as a whole, the evidence is limited to one study and is associated with a high risk of bias. This was compounded by the fact that the effect of cluster randomisation was not accounted for in the analysis. Furthermore, no robust evidence was identified to support the use of other adjunctive technologies like toluidine blue, brush biopsy or fluorescence imaging within a primary care environment. Further randomised controlled trials are recommended to assess the efficacy, effectiveness and cost-effectiveness of a visual examination as part of a population based screening programme.

Screening programmes for the early detection and prevention of oral cancer

BACKGROUND

Screening programmes for major cancers, such as breast and cervical cancer have effectively decreased the mortality rate and helped to reduce the incidence of these cancers. Although oral cancer is a global health problem with increasing incidence and mortality rates, no national population-based screening programmes for oral cancer have been implemented. To date there is debate on whether to employ screening methods for oral cancer in the daily routine work of health providers.

OBJECTIVES

To assess the effectiveness of current screening methods in decreasing oral cancer mortality.

SEARCH STRATEGY

Electronic databases (MEDLINE, CANCERLIT, EMBASE, the Cochrane Central Register of Controlled Trials; 1966 to July 2005, The Cochrane Library - Issue 3, 2005), bibliographies, handsearching of specific journals and contact authors were used to identify published and unpublished data.

SELECTION CRITERIA

Randomised controlled trials of screening for oral cancer or precursor oral lesions using visual examination, toluidine blue, fluorescence imaging or brush biopsy.

DATA COLLECTION AND ANALYSIS

The search found 112 citations and these have been reviewed. One randomised controlled trial of screening strategies for oral cancer was identified as meeting the review's inclusion criteria. Validity assessment, data extraction and statistics evaluation were undertaken by two independent review authors.

MAIN RESULTS

One 10-year randomised controlled trial has been included (n = 13 clusters: 191,873 participants). There was no difference in the age-standardised oral cancer mortality rates for the screened group (16.4/100,000 person-years) and the control group (20.7/100,000 person-years). Interestingly, a significant 34% reduction in mortality was recorded in high-risk subjects between the intervention cohort (29.9/100,000 person-years) and the control arm (45.4/100,000). However, this study has some methodological weaknesses. Additionally, the study did not provide any information related to costs, quality of life or even harms of screening from false-positive or false-negative findings.

AUTHORS' CONCLUSIONS

Given the limitation of evidence (only one included randomised controlled trial) and the potential methodological weakness of the included study, it is valid to say that there is insufficient evidence to support or refute the use of a visual examination as a method of screening for oral cancer using a visual examination in the general population. Furthermore, no robust evidence exists to suggest that other methods of screening, toluidine blue, fluorescence imaging or brush biopsy, are either beneficial or harmful. Future high quality studies to assess the efficacy, effectiveness and costs of screening are required for the best use of public health resources. In addition, studies to elucidate the natural history of oral cancer, prevention methods and the effectiveness of opportunistic screening in high risk groups are needed. Future studies on improved treatment modalities for oral cancer and precancer are also required.

Economic impact of screening for bladder cancer using bladder tumor markers: A decision analysis

PURPOSE

The Food and Drug Administration recently approved the use of bladder markers such as BladderChek (NMP22; Matritech, Inc., Newton, MA) and UroVysion (Abbott Laboratories, Abbott Park, IL) for use in screening for bladder cancer. The purpose of this analysis was to assess the cost associated with implementing a widespread screening program using a noninvasive bladder tumor marker.

METHODS

Data for the accuracy of NMP22 in detecting bladder cancer was gathered from a comprehensive literature review. A decision tree analysis was constructed to evaluate the total cost of screening a low and high-risk population for bladder cancer using NMP22. Sensitivity analyses were conducted to evaluate the effect of relaxing the various assumptions in the model.

RESULTS

Application of the model to all men, regardless of the degree of risk, rendered a cost per cancer detected of $783,913, $269,028, and $139,305 for ages 50-59, 60-69, and 70-79 years, respectively. Screening only patients at high-risk for bladder cancer (annual incidence 6%) would yield a cost per cancer detected of $3,310. Incidence of cancer and marker specificity had the highest influence on cost per cancer detected.

CONCLUSIONS

Application of NMP22 to the entire population would render an extremely high cost per cancer detected. However, application to an appropriate high-risk target population could achieve cost per cancer detected comparable to currently used screening programs for prostate, colon, and breast cancer. Further studies are needed to assess the accuracy of bladder tumor markers in detecting bladder cancer in a completely asymptomatic cohort.

Detection and quantification of mutations in the plasma of patients with colorectal tumors

The early detection of cancers through analysis of circulating DNA could have a substantial impact on morbidity and mortality. To achieve this goal, it is essential to determine the number of mutant molecules present in the circulation of cancer patients and to develop methods that are sufficiently sensitive to detect these mutations. Using a modified version of a recently developed assay for this purpose, we found that patients with advanced colorectal cancers consistently contained mutant adenomatous polyposis coli (APC) DNA molecules in their plasma. The median number of APC DNA fragments in such patients was 47,800 per ml of plasma, of which 8% were mutant. Mutant APC molecules were also detected in >60% of patients with early, presumably curable colorectal cancers, at levels ranging from 0.01% to 1.7% of the total APC molecules. These results have implications for the mechanisms through which tumor DNA is released into the circulation and for diagnostic tests based on this phenomenon.