Devita, Hellman, and Rosenberg's Cancer

LWBK1006-13 LWW-Govindan-Review November 24, 2011 11:22

146 DeVita, Hellman, and Rosenberg’s CANCER: Principles and Practice of Oncology Review

presence or absence of a disease is unknown, and the pertinent question

is the accuracy of the test result. The PPV or PV+is an estimate of the

accuracy of the test in predicting the presence of disease; the negative

predictive value (NPV or PV–) is an estimate of the accuracy of the test

in predicting the absence of disease. The PPV represents the proportion

of all positive tests that are true positives: TP/(TP+FP). A PPV of 10%

means that 10% of positive test results are true positives, so 90% are false

positives.

Answer 13.7. The answer is C.

The sensitivity and specificity are characteristics of the test itself and are

not affected by the population characteristics. On the other hand, the PPV

and NPV values are influenced by the disease prevalence in the population

being tested.

Answer 13.8. The answer is A.

Fecal occult blood testing and flexible sigmoidoscopy have been proven

effective in randomized controlled trials. For the other screening modal-

ities, the only published data are from observational and case-control

studies. There are ongoing randomized controlled trials of colonoscopy,

but no data are yet available.

Answer 13.9. The answer is A.

Patients with a second-degree relative diagnosed with colon cancer

are not at increased risk for developing colorectal cancer. The screen-

ing recommendations for this group are same as that for the general

population.

Answer 13.10. The answer is D.

HPV infection is common in young, sexually active women but is often

transient. Up to 70% of high-risk HPV infections will resolve sponta-

neously. Similarly, up to 90% of LSILs will regress without treatment.

Concerns have been raised that screening young women could lead to

overdiagnosis, aggressive treatment, and unnecessary harm from ablative

surgical procedures.

Answer 13.11. The answer is D.

No screening strategies have been shown to be effective for screening for

ovarian cancer for several reasons. Ovarian cancer has a low prevalence

in the population, thus lowering the PPVs of any tests. CA 125 has lim-

ited sensitivity (it misses many early-stage cancers) and limited specificity

(many false positives). Transvaginal ultrasound has inadequate specificity.

Answer 13.12. The answer is B.

The United States Preventive Services Task Force, the American College

of Obstetricians and Gynecologists, and the American College of Physi-

cians all discourage routine screening for ovarian cancer in the general