Existing Cancer Screening Methods

A complete summary of cancer detection/screening methods may be found on the National Cancer Institute’s website:

https://www.cancer.gov/publications/pdq/information-summaries/screening

Below is our summary of the pros and cons of the most common types of cancer, based on information gathered from several sources:

Colorectal Cancer [AACR]

  • Stool-based test – Convenient and low cost but has a high false-positive rate
  • Sigmoidoscopy – video camera in colon/rectum to look for polyps
    • Semi-invasive
    • Doesn’t require bowel preparation or sedation
    • Screens only distal colon (rather than entire colorectum)
  • Colonoscopy – video camera in colon/rectum to look for polyps
    • Invasive, can cause tears in lining
    • Requires bowel preparation
    • Requires sedation
    • Potential complications
    • High cost
  • CT colonography – type of x-ray
    • Exposure to radiation
    • Requires bowel preparation
    • High cost, not covered by Medicare
  • Double-contrast barium enema – type of x-ray
    • Radiation exposure
    • Semi-invasive – Bloating/cramping/constipation afterwards


Prostate Cancer

  • PSA blood test (Prostate-Specific Antigen)
    • Increased PSA level can be caused by benign prostate conditions. Most men with elevated PSA level do not have prostate cancer. [NCI]
    • US Preventive Services Task Force recommends against PSA test (harms outweigh the benefits)
    • Up to 85% false positive
  • DRE (Digital Rectal Exam)
    • Uncomfortable
    • Not accurate although it can find cancer in those who have normal PSA levels [AACR]


Breast Cancer
– Early detection permits women to choose less treatment

  • Mammogram
    • The benefits of screening mammography vary by age. Women ages 50-69 get the most overall benefit for a number of reasons. Getting regular screening mammograms lowers the risk of dying from breast cancer, but it doesn’t completely remove the risk. [Susan G. Komen]
    • Up to 54% of breast cancers detected by mammograms are estimated to be overdiagnosis, or false positives. [NCI]
    • 50% of women screened annually for 10 years in the US will experience a false positive, of whom 7-17% will have biopsies. [NCI]
    • Potential false negatives: Dense breast tissue shows up as white, making it hard to see white tumors. [NCI]
    • Radiation exposure [NCI]
    • Mammogram machine cost = $500K to $1 million
    • Tomosynthesis (3-D) screening is more accurate and has a lower callback rate for patients but has higher radiation levels than traditional and 2-D screenings [AACR]
    • After a woman has bilateral mastectomy without nipple sparing, a mammogram is not useful to screen for breast cancer recurrence [AACR]
  • Self breast exam [Susan G. Komen]
    • Self-exam no longer recommended
    • No difference in breast cancer survival
    • Women who did BSE had more false positive results (which led to nearly twice as many biopsies with negative (no cancer found) results)
  • Clinical breast exam
    • Clinical breast examination (CBE) has not been tested independently; it is not possible to assess the efficacy of CBE as a screening modality when it is used alone versus usual care (no screening activity).
    • May lead to false positives: Specificity in women aged 50 to 59 years was 88% to 99%, yielding a false-positive rate of 1% to 12%.
    • May lead to false negatives: Of women with cancer, 17% to 43% have a negative CBE.

     

  • Supplemental Imaging [AACR]
    • Magnetic Resonance Imaging – not always accurate; recommended for high-risk patients in conjunction with other screening tests
    • Sonograms (breast ultrasound) – useful in evaluating dense breasts but a breast ultrasound is not useful for detecting the microcalcifications seen in early breast cancer. It is best used for the evaluation of a breast lump or other breast symptoms.
    • Molecular Breast Imaging – still new, not much data


Lung Cancer
[NCI]

  • Low-dose helical computed tomography
    • 16% relative reduction in lung-cancer specific mortality
    • Approximately 96% of all positive low-dose helical computed tomography screening exams do not result in a lung cancer diagnosis. False-positive exams may result in unnecessary invasive diagnostic procedures.
    • Based on the findings from a large randomized trial, the average false-positive rate per screening round was 23.3%.
  • Chest X-ray and/or sputum cytology
    • Screening with chest x-ray and/or sputum cytology does not reduce mortality from lung cancer in the general population or in ever-smokers.
    • At least 95% of all positive chest x-ray screening exams do not result in a lung cancer diagnosis.
    • A modest but non-negligible percentage of lung cancers detected by screening chest x-ray and/or sputum cytology appear to represent overdiagnosed cancer; the magnitude of overdiagnosis appears to be between 5% and 25%.

 

Ovarian Cancer [NCI]

  • CA-125 tumor marker – Results from the PLCO trial showed that CA-125, a tumor marker that is sometimes elevated in the blood of women with ovarian cancer but can also be elevated in women with benign conditions, is not sufficiently sensitive or specific to be used together with transvaginal ultrasound to screen for ovarian cancer in women at average risk of the disease.