Cancer Screening & Early Cancer Detection in 2020

cancer screening and early cancer detection

Introduction

For more than a half-century, cancer screening has been an important component of the struggle to reduce the burden of morbidity and mortality from cancer.

In certain cases, such as with cervical cancer, the effects have been dramatic, with mortality decreasing more than 80% in the United States after implementation of widespread screening with Pap smears. For most other cancers, however, the effects of screening have been substantially less pronounced.

The benefits of screening have generally been on the modest side, and there has been increasing recognition of screening related harms. The promise of cancer screening still beckons, however, and many new technologies continue to be evaluated for their potential to generate new screening modalities.

The goal of cancer screening and early detection is to cure cancer by detecting the malignancy, or its precursor lesion, at an early stage, before the onset of symptoms, when treatment of cancer is most effective.

Indeed, overall cancer mortality has decreased by 25% from 1990 to 2015 in the United States (US), with even greater declines in the mortality rates for colorectal cancer (47% among men and 44% among women) and, breast cancer (39% among women).

A portion of this decrease can be attributed to the introduction of high-quality cancer screening for colorectal and breast cancer. The most successful cancer screening programs lead to the identification of precursor lesions (eg, cervical intraepithelial neoplasia with cervical cancer screening and colonic polyps with colorectal cancer screening), where the treatment of the precursor lesion leads to a decrease in the incidence of invasive cancer over time.

The guiding principles of screening for the disease were proposed in 1968 by Wilson and Jungner2 of the World Health Organization. Not all cancer screening recommendations meet each of these guiding principles; historically there has been a balance between the identification of early or precursor lesions and the avoidance of overdiagnosis, which may lead to overtreatment.

American Cancer Society Recommendations for the Early Detection of Cancer

The American Cancer Society (ACS) provides an annual report for health care professionals and the public that summarizes the current ACS cancer screening guidelines, including current recommendations, updates, and guidance related to early cancer detection when a direct recommendation for screening cannot be made.

This annual report also includes the most recent data on cancer screening rates and a discussion of timely issues related to early cancer detection.

CANCER SITEPOPULATIONTEST OR PROCEDURE
BreastWomen aged 40-54 y     Women aged 55 yMammography     Mammography
CervixWomen, aged 21-29 y   Women, aged 30-65 y   Women aged >65 yPap test   Pap test and HPV DNA test   Pap test and HPV DNA test    
ColorectalMen and women, aged 45-75 y, for all tests listedFecal immunochemical test (FIT) [annual], or High-sensitivity guaiac-based fecal occult blood test (HSgFOBT) [annual], or Multitarget stool DNA test (mt-sDNA), [every 3 y per manufacturer’s recommendation], or Colonoscopy [every 10 y], or CT colonography (CTC) [every 5 y], or Flexible sigmoidoscopy (FS) [every 5 y
LungCurrent or former smokers aged 55-74 y in good health with at least a 30-pack-y history of smokingLow-dose helical CT
ProstateMen, aged ≥ 50 yProstate-specific antigen test (PSA) with or without digital rectal examination (DRE)

American Cancer Society Recommendations for the Early Detection of Cancer in Average-Risk Asymptomatic Adults.

Tumor Markers Commonly Used for Screening or Surveillance        

Tumor markers have been used for decades in oncology. Tumor markers are biomarkers found in blood, urine, cerebrospinal fluid, or other body tissues that are elevated in association with cancer. Tumor markers can, in theory, be used for screening, diagnosis, staging, or disease monitoring.

BiomarkerCancers
Alpha-fetoproteinGerm cell tumors and hepatocellular carcinoma
Beta-human chorionic gonadotropinChoriocarcinoma and testicular cancer
Beta-2 microglobulinMultiple myeloma, chronic lymphocytic leukemia, and some lymphomas
CA-125Ovarian
CA-15.3, CA2-7.29Breast
CA-19.9Pancreas, gall bladder and bile duct, and gastric
CD20Non-Hodgkin lymphoma
CalcitoninMedullary thyroid
Carcinoembryonic antigenOvarian, cervix, breast, urinary tract, gastrointestinal, and lung
Lactate dehydrogenaseGerm cell tumors
Prostate-specific antigenProstate

Tumor Markers Commonly Used for Screening or Surveillance.

Potential benefits and harms of cancer screening

Perceived harms and benefits of screening influence the decision to be screened, especially when recommendations explicitly suggest that harms and benefits should be weighed in the decision, as with shared decision making, defined as an approach where medical decisions are made by clinicians and patients together based on the best available evidence.

Potential Benefits of Cancer Screening

The main benefit of screening is earlier detection of cancer, which can be easier to treat, leading to reduced cancer-specific mortality. As we discussed above, there is evidence that mammography screening reduces breast cancer-specific mortality (Nelson et al., 2016), cervical cancer screening tests, including Pap tests and HPV testing, reduce cervical cancer-specific mortality (Melnikow et al., 2018), and colorectal cancer screening tests reduce colorectal cancer-specific mortality (Lin et al., 2016).

Also, there may be reassurance or affective benefits experienced with a negative test result. Despite these potential benefits, however, there are potential downsides to screening as well.

Potential Harms of Cancer Screening

Psychological science has contributed much to our understanding of how harms of screening are perceived and how they may influence the decision to screen. Here, we 8 E. A. SARMA ET AL. consider the evidence for physical and psychological harm through the screening process: at the time of the screening test, at the time of receiving results, and after receiving test results.

Since screening is not a single event, the perception or experience of harm at any point in the screening process can discourage initial or repeat screening.

References

  1. Pinsky, P. F. (2015). Principles of Cancer Screening. Surgical Clinics of North America, 95(5), 953–966. doi:10.1016/j.suc.2015.05.009 
  2. Loud, J. T., & Murphy, J. (2017). Cancer Screening and Early Detection in the 21 st Century. Seminars in Oncology Nursing, 33(2), 121–128.
  3. Smith, R. A., Andrews, K. S., Brooks, D., Fedewa, S. A., Manassaram-Baptiste, D., Saslow, D., … Wender, R. C. (2018). Cancer screening in the United States
  4. Schiffman, J. D., Fisher, P. G., & Gibbs, P. (2015). Early Detection of Cancer: Past, Present, and Future. American Society of Clinical Oncology Educational Book, (35), 57–65. doi:10.14694/edbook_am.2015.35.57 
  5. Elizabeth A. Sarma, Michelle I. Silver, Sarah C. Kobrin, Pamela M. Marcus & Rebecca A. Ferrer (2019): Cancer screening: health impact, prevalence, correlates, and interventions, Psychology & Health, DOI: 10.1080/08870446.2019.1584673