CANCER SCREENINGPART I

AIMGP Seminar Series

January, 2004

Joo-Meng Soh

Edited by Gloria Rambaldini

CASE #1Your father has just turned 50 years old and his family doctor is recommending prostate cancer screening tests.

He has been reading the newspapers and came across the following article:

Toronto Star, Dec. 31, 2001

CASE #1

a) No ... the health care system can’t afford itb) Yes – go for a Digital Rectal Examc) Yes – go for a PSA testd) Yes – go for a DRE and a PSAe) Don’t know – I haven’t been through AIMGP

Cancer Screening Guidelines Part I yet....

He asks you if he should be screened and what tests he should undergo...

You tell him:

OBJECTIVES• Understand the concept of cancer

screening and the controversies surrounding this topic

• To learn the Canadian screening guidelines for Prostate and Cervical cancer

• To be aware of other cancer screening guidelines available

Principles of Cancer Screening

• Screening of asymptomatic individuals to detect early cancers which may be curable

• Use of diagnostic tests of high sensitivity• Diagnostic tests are suitable to the patient• Natural history of disease can be

changed by intervention• Proposed early treatment should be

beneficial and not harmful to the patient

Guidelines Available

Website: http://www.ctfphc.org

Guidelines Available

http://www.hc-sc.gc.ca/hppb/healthcare/pubs/clinical_preventive/

Prostate Cancer• 2nd most frequent cause of cancer-

related deaths among males • Rapid rise in incidence over age 60• Lifetime risk of developing prostate

cancer=16 %; risk of dying 3%• Many cases not clinically evident:

– at autopsy prostate CA in one-third of men<80, two-thirds men >80

• Prostate CA grows slowly: most men die of other causes

Prostate CancerCanadian Statistics:

• Estimated New cases for 2001: 17 800

• Estimated Deaths for 2001: 4300

Canadian Cancer Statistics 2001 Website: http://66.59.133.166/stats/maine.htm

Options for Screening

• Digital Rectal Examination

• Prostate-Specific Antigen (PSA)

• Trans-Rectal UltraSound (TRUS)– not recommended as a screening tool

primary use is to guide biopsies

Digital Rectal Examination• Sensitivity Poor

• 40-50% of cancers are out of reach

• Inter-rater reliability low-moderate

• PPV 15-30%, NPV even lower

NOTE:

Since Gold Standard Test is prostatectomy or extensive biopsy, Sens. & Spec. cannot be accurately determined Positive and Negative Predictive Values are used instead

Prostate Specific Antigen• Produced by epithelial cells of prostate• Levels > 4.0 ng/mL “suspicious”• Physicians' Health Study (22,000

men with long-term follow-up)– sensitivity of a single baseline PSA

>4.0 ng/mL approximately 73% for any prostate cancer

– 87% for aggressive cancers – Canadian data suggests high false

positive rates

Prostate Specific Antigen• Positive Predictive Value:

– If PSA 4-10: 22%– If PSA >10:40-60%

• Conditions which increase PSA levels– BPH, DRE– TRUS, Biopsy– Prostatic infection, recent ejaculation

Prostate Specific Antigen

• As PSA levels increase:– Odds of cancer increase– Odds of extra-capsular or metastatic

disease increase– Odds of “cure” decrease if it is cancer

PSA - Pros

• Detect cancer early, while still curable

PSA - Cons• No evidence for a

reduction in morbidity or mortality

• Positive test may result in unnecessary tests and treatments

PSA – Cons• Treatment of early stage cancer may

have no impact on overall survival

• Even combined with DRE, PPV not substantially higher (20%)

• Possible harms with treatment (prostatectomy or radiation therapy):

– impotence, urinary incontinence,

peri-operative morbidity/mortality

Prostate Screening Guidelines Variety of Recommendations exist:

AAFP American Academy of Family Physicians ACP-ASIM American College of Physicians-American Society of

Internal Medicine ACS American Cancer Society AUA American Urological Association AMA American Medical Association CTFPHC Canadian Task Force on Preventive Health Care USPSTF U.S. Preventive Services Task Force

Recommendations• Canadian Task Force on Preventative

Health Care:

“Based on the absence of evidence for effectiveness of therapy and the substantial risk of adverse effects of associated with such therapy and the poor predictive value of screening tests, there is at present insufficient evidence to support wide-spread initiatives for the early detection of prostate cancer.”

Recommendations

ACP-ASIM gives a pragmatic compromise:

“Physicians should describe potential benefits and known harms of screening, diagnosis, and treatment; listen to the patient’s concerns, then individualize the decision to screen”

Counseling Patients• Prostate Cancer is an important health

problem

• Benefits of Screening are unproven

• DRE & PSA can have false positives and false negatives

• Probability of further invasive evaluation is high (around 15%)

Counseling Patients

• If a tumour is found, aggressive therapy (along with its risks/complications) is necessary to realize any benefit

• Early detection may save lives and avert future cancer-related illness

Counseling Patients• Ministry of Health and Longterm Care

provides information for patients:

• Available through ICES Website:http://www.ices.on.ca/

Back to the Case• Review the data

• Discuss the options with the family doctor

• Then make an informed decision on whether or not to undergo screening

CASE #262 y.o. widowed female with two healthy children

She says, “I’m 62 years old now and no longer sexually active. My last two PAP tests were negative.” She asks ”Do I really need another one? Will this ever end???”

CASE #2You tell her:

a) No – you are too old for it now

b) No – because your last two were negative

c) Yes – every year

d) Yes – every 3 years

e) I don’t know yet.....but I’ll tell you in 5 minutes (after the end of this

seminar)

Guidelines Available

Cervical Cancer• 11th most common cancer among

women in Canada

• Canada, 1993:– 1300 women developed cervical cancer– 400 women died of the disease

Canadian Statistics:

• Estimated New cases (2001): 1450

• Estimated Deaths (2001): 420

Cervical Cancer• Risk Factors

– early age at first sexual intercourse (<17y/o)– multiple sexual partners (>2)– smoking– low socioeconomic status– HPV Infection (Types 16, 18, 31, 39, 45, 56, 58,

59, 68)– Hx STDs– Hx other lower genital tract neoplasia– Radiation– Immunosuppression– OCPs

Cervical Cancer Screening• Papanicolaou Smear Test

• High False Neg. Rate: up to 25%– Sampling error (failure of MD to obtain

malignant cells from the cervix; failure to take samples from the squamo-columnar junction)

– Lab Error

• Note: testing for HPV not currently recommended

The Evidence• No RCT’s- due to the widespread use of

this screening test

• Only Cohort and Case-control studies provide evidence for a reduction in the incidence of invasive disease

• Optimal frequency of screening is less known

Cervical Cancer Screening Guidelines

AAFP: American Academy of Family Physicians ACOG: American College of Obstetricians and Gynecologists ACS: American Cancer Society AMA: American Medical Association CTFPHC:Canadian Task force on Preventive Health Care USPSTF: U.S. Preventive Services Task Force

Canadian GuidelinesAddendum

• Consider screening more frequently in high risk women (due to the high FN rate and the variable rate of progression of disease)

• The largest group of women at risk of dying from cervical cancer are those who have never been screened before

BACK TO THE CASE• Continue screening every 3 years until

the age of 69

• The Pap tests will eventually end....

Principles of Cancer Screening

• Screening of asymptomatic individuals to detect early cancers which may be curable

• Use of diagnostic tests of high sensitivity• Diagnostic tests are suitable to the patient• Natural history of disease can be

changed by intervention• Proposed early treatment should be

beneficial and not harmful to the patient