Cancer Screening and Biases Overview

Study Notes

Lead Time Bias: Apparent increased survival attributed to earlier detection of a disease.
Length Time Bias: Occurs when slower-growing cancers are more likely to be detected through screening, creating a false impression of longer survival in screened populations.

Positive Predictive Value: Percentage of patients who test positive and actually have the disease.
Negative Predictive Value: Percentage of patients who test negative and do not have the disease.
Sensitivity: Ability to accurately identify individuals who have the disease.
Specificity: Ability to accurately identify individuals who do not have the disease.

Most Important Risk Factor: Age is the single most important risk factor for developing breast cancer.
- One first-degree relative with breast cancer doubles the risk; two or more quadruples it.
Screening Recommendations:
- Begin breast cancer screening at age 40, per the American Cancer Society and National Cancer Institute.
- American College of Physicians and U.S. Preventive Services Task Force recommend individualized discussions for women aged 40-49, without routine mammography recommendations for this age.
Mammography False Negative Rate: Approximately 10%. All palpable masses require further evaluation through ultrasound, even with an unremarkable mammogram.

Conditions for MRI:
- Women aged 25-30 or older with a known BRCA mutation.
- First-degree relatives of individuals with a known BRCA mutation.
- Patients who underwent chest irradiation between ages 10-30.
- Individuals with over 20% lifetime breast cancer risk according to clinical risk predictions.

Family History Guidelines:
- Initiate screening colonoscopy at age 40 if a first-degree relative was diagnosed with colorectal cancer before age 60, or 10 years earlier than the age of diagnosis in the family member.
Screening Intervals:
- For individuals with a first-degree relative diagnosed with colorectal cancer before age 60, repeat colonoscopy is every 5 years if initial screening is normal.
- If normal or hyperplastic polyps are found, repeat colonoscopy is recommended every 7-10 years.

Age to Stop Screening: Prostate cancer screening is typically discontinued for individuals over 75 years of age.
PSA and Biopsy Decision: Assess PSA velocity, particularly if the PSA value exceeds 4.0 ng/ml and increases by more than 1 ng/ml per year, suggesting the need for a prostate biopsy.

Eligibility for Screening: Recommended for current or former smokers (quit within the last 15 years) aged 55-74 with a 30 pack-year smoking history (ACS guidelines) or aged 55-80 (USPSTF guidelines).