CANCER SCREENINGSudarsaDepartment of Surgery, Faculty of Medicine University of Udayana / Sanglah General Hospital Denpasar 2012

COLORECTAL CANCER

INTRODUCTIONCancer is a major public health problem in the developed countries. The second leading of death after Cardiovascular disease.One of WHO priority program for cancer control is Cancer screening.Screening for Cancer: whats new and controversies?

W.H.O. Priority Program for Cancer Control.Primary Prevention ( Public Education, Professional Education, Political Will Government)

Secondary Prevention ( Early Detection screening program: Individual & Mass Screening).

Tertiary Prevention (Correct Diagnosis and prompt treatment) good professional training and education patient volume, and learning curve first appropriate attempt for treatment the best chance for cure.

Palliative Management especially pain management.

PRINCIPLES OF CANCER SCREENINGScreening test is performed on asymptomatic individual to determine that cancer might be present and that further evaluation is necessary.Screening must find disease earlier and lead to an efficacious treatment.Earlier use of the efficacious treatment must offer better outcome.The ultimate purpose of screening is to reduce mortality.Potential bias of screening: Selection, Lead-time, length-time bias.

TYPE OF SCREENING FOR CANCERINDIVIDUAL SCREENING

MASS SCREENING

Screening Test VS Diagnostic TestScreening test:- Initiated by providers- Easy and quick

- Cheaper- High sensitivity and specificity- Acceptable by community- For large population- Followed by further diagnostic testDiagnostic test- Initiated by patients- From easy to sophisticated- More expensive- High accuracy

- May not accepted- Especially for individual- Not followed by any test

Characteristic of the Ideal Screening ProgramFeatures of the disease:Significant impact on public healthAsymptomatic period during which detection is possibleOutcome improved by treatment during asymptomatic period

Feature of the test:Sufficiently sensitive to detect disease during asymptomatic periodSufficiently specific to minimize false positive test resultsAcceptable to patients

Features of screened population:Sufficiently high prevalence of the disease to justify screeningRelevant medical care is accessible

Patients willing to comply with further work-up and treatment

From: Gates JT. Screening Cancer: Evaluation of Evidence. Am Fam Physician 2001;63:513-22.

Potential Biases of ScreeningSeveral biases of screening: Selection, Lead-time,

Length-time bias.

SELECTION BIAS:Occurs when a group of individuals comes forward to be screened.

The individuals are at higher risk getting cancer, The individuals have better underlying health.

Lead time bias:Occurs when the asymptomatic period in the natural history of the disease is not taken into account.Survival statistics prone to lead-time biasThe time from diagnosis to death is increasedTreatment does not prolong overall lifeThe patient does not live longerThe patient is merely diagnosed at an earlier date.The Scheme :

LEAD TIME BIAS

From: Gates JT. Screening Cancer: Evaluation of Evidence. Am Fam Physician 2001;63:513-22.

Length time bias:Occurs because of heterogeneity of diseases.Occurs when slow-growing, less aggressive cancer are detected during screening.Interval Cancers are more aggressive, and treatment outcomes are not favorable. The scheme:

LENGTH TIME BIAS

From: Gates JT. Screening Cancer: Evaluation of Evidence. Am Fam Physician 2001;63:513-22.

SCREENING FOR CERVICAL CANCERPAPANICOLAOU (PAP) SMEAR- Prototype of a successful cancer screening program- 80% decrease in mortality caused by cervical cancer- Recommended interval 1-3 years- Regularly for women who are sexually active over age 18 yrs- ACS: Begin 3 yrs after the onset of vaginal intercourse.- NO RCTs

New methode: Liquid based Pap test Asetic Acid HVP-DNA test.

Current controversies: Proper interval of Pap smear, when to stop. Role of new technology HPV Vaccine ???

SCREENING FOR BREAST CANCERStudy of BSE and CBE have not shown a decrease in mortality (Cochrane review)Mammographic screening normal-risk women over 50 years every 1 year decrease mortality 20-30%.Mammographic screening for women aged 40-49 years, still controversy. (Meta-analysisno benefit of mammographic screening)High breast density is associated with diminished sensitivity.Women at high risk: Earlier initiation, short interval, and with add modalities (MRI).Mammographic screening may not sensitive in women carrying BRCA1/BRCA2 gene mutations.See ACS guidelines

SCREENING FOR COLORECTAL CANCERACS guideline for colorectal screening.RCTs for FOBT 33% reduction in RR of death.

other RCTs 15-18%.FOBT and FITNo RCTs for Flexible sigmoidoscopyDRE or Barium enema as CRC screening?New methods: Virtual colonoscopy or CT colonography. DNA methylation, Gene mutation.The role of screening in high risk population?Controversy: high cost.

SCREENING FOR PROSTATE CANCERDRE and PSA, annually, starting at age 50 years.Prostate cancer prone to lead-time bias, length bias, and over diagnosis.There was insufficient evidence in support of prostate cancer screening.PSA: prostate tissue specific. Normal level 0-4ng/dL. Cutoff value for screening 2,5ng/dL?ACS recommendation: Normal-risk men > 50 years be offer screening and be allowed to make choice after being informed of potential risks and benefits of screening.

Screening for Lung CancerNo standard screening methods for lung cancerChest x-rays, sputum cytology or both.No reduction in mortality was seen in screened population (Cochrane review)Spiral CT screening and PET as adjunct to spiral CT in asymptomatic smokers ACS: no recommendation of screening for lung cancer.

Brawley OW, Kramer BS. Cancer Screening in Theory and in Practice. J Clin Oncol 2005;23:293-300.

Gates TJ. Screening for Cancer: Evaluating the Evidence. Am Fam Physician 2001;63:513-22.

PRECANCEROUS LESIONS

CHEMOPREVENTION ?

SUMMARYThe important role of primary care provider in cancer screening.A screening test is performed on an asymptomatic individual and more complicated than diagnostic test.The purpose of screening is to reduce mortalityUnderstanding of evidence and potential bias of screening.Advances in cancer biology and medical imaging have led to number of cancer screening test.In the future, proteomic technology also can be used for cancer screening.

EDUCATION IS STRONGEST WEAPON AGAINST CANCER