By Dr. Robert Ali, Kymera Independent Physicians
Despite advances in technology, science, and research, cancer continues to be a global epidemic plaguing society. Moreover, it remains one of the leading causes of death worldwide. Cancer Screenings are a vital element in the battle.
Sobering Cancer Statistics
According to statistics from the National Cancer Institute, last updated in April 2018, an estimated 1,735,350 new cases of cancer will be diagnosed in the United States in 2018; 609,640 people succumb to the disease. A more in-depth break down of these figures reveals:
- The number of new cases of cancer (cancer incidence) is 439.2 per 100,000 men and women per year. These figures are based on 2011-2015 environmental studies.
- The number of cancer deaths (cancer mortality) is 163.5 per 100,000 men and women per year based on 2011-2015 deaths.
- Cancer mortality is higher among men than women (196.8 per 100,000 men and 139.6 per 100,000 women)
- The estimated national expenditure for cancer care in the United States was $147.3 billion in 2017.
- The most common cancers in descending order are breast cancer, lung cancer, prostate cancer, colon/rectum cancer, melanoma of the skin, and others. (1)
Given these sobering statistics, we thought it worthwhile to focus this month’s cancer awareness edition on SCREENING.
What is Cancer Screening?
In simple terms, screening refers to an evaluation of cancer before someone experiences symptoms. By extension, cancer screening also has utility in detecting pre-malignant conditions. These include benign lesions with the potential to become cancerous if left unattended. The goals of screening are three-fold:
- To reduce the number of people who die from disease and prevent deaths from cancer altogether
- Reduce the number of people who develop the disease
- Offer treatment with a curative intent for early stage disease
Moreover, screening tests are usually unique for the specific cancer site in question. For instance, The test can be tailored according to
- Type (breast, colorectal, lung, etc.)
- Family history
- Genetic risk factors and
- Environmental exposure (tobacco exposure being one of the largest culprits).
The actual screening tests are varied and can range from simple blood analyses to imaging studies like mammograms or low dose CT scans to more invasive interventions including colonoscopies.
Consider now screening for the following three malignancies – BREAST CANCER, CERVICAL CANCER, and COLORECTAL CANCER.
BREAST CANCER SCREENING
The average lifetime risk of breast cancer for a woman in the United States has been estimated at 12.3 % (that is, 1 in 8 women) (2). The American Cancer Society estimates 268,670 new cases of invasive breast cancer (266,120 women and 2,550 men) and 41,400 deaths secondary to breast cancer for 2018 (3).
The components of a breast screening evaluation are dependent on an interplay of factors. These include age, prior medical history, as well family history. Factors can also encompass personal breast awareness (patient’s familiarity with her breasts), clinical breast examinations (CBE), mammography, and in certain circumstances, breast magnetic resonance imaging (MRI).
Mammography remains the most important imaging modality for breast cancer screening. In fact, it is the only one to demonstrate a mortality reduction.
A mammography screening typically entails two x-ray images of each breast, one from the top (referred to as, craniocaudal) and one from the side (mediolateral oblique). Digital mammography has largely replaced film-screen mammography. This enhances the ability to detect subtle abnormalities and allow comparison of serial examinations.
More recently, the introduction of digital breast tomosynthesis has further improved cancer detection rates, while reducing the false positive rate. Tomosynthesis employs a moving x-ray and digital detector to generate three-dimensional (3D) data.
Dense breast tissue limits adequate mammographic evaluation as it can obscure visualization of underlying small lesions. Breast ultrasound has emerged an adjunctive diagnostic tool to help circumvent this drawback. Breast MRI is an additional diagnostic tool that can be employed, however, it is usually reserved for specific cases (see below).
Various screening recommendations have been put forth, but those advocated by the National Comprehensive Cancer Network (NCCN) for women at average risk are as follows:
ANNUAL SCREENING MAMMOGRAPHY BEGINNING AT AGE 40 YEARS.
There remains a sub-group of women who are at a higher risk of developing breast cancer and require more rigorous screening. Established risk factor models provide a risk factor projection on the basis of several factors. These include
- age of first live birth or nulliparity
- number of first degree relatives with breast cancer
- number of previous benign breast biopsies
- previous atypical hyperplasia and
The interpretation of such models should be undertaken under the supervision of a physician.
These higher risk women include those with a:
- Prior personal history of breast cancer
- Previous radiation therapy to the chest wall before age 30 years old (e.g. for lymphoma)
- Lifetime risk of at least 20% (based on defined models)
- Prior diagnosis of lobular carcinoma in situ (LCIS) or atypical ductal/lobular hyperplasia (ADH/ALH) and >20% life time risk
- Highly suggestive or known genetic predisposition (e.g. BRCA mutation)
In the event that an abnormality is detected on screening imaging, this should be followed with either the local interventional radiologist or surgeon. Tissue acquisition is often mandatory to ascertain a diagnosis, and can be accomplished via various procedures, namely a fine needle aspiration, core needle biopsy or excisional biopsy. Further work-up will be dictated by the results of the biopsy.
CERVICAL CANCER SCREENING
Historically, cervical cancer was one of the leading causes of cancer death for women in the U.S. However, with the advent of cervical cancer screening via Pap smears and an emphasis on public health awareness, the number of cases of cervical cancer, as well as the number of deaths, have significantly declined over the past 40 years.
In 2016, the CDC quotes 12,984 new cases of cervical cancer reported in the U.S., with 4,188 women dying from the disease. Moreover, the incidence seems to be particularly predominant among the Hispanic and black populations.
The cervix is the opening of the uterus located at the top of the vagina and screening entails evaluation for suspicious-looking cells at this area. This is referred to as cervical cytology, or more commonly, the Pap smear test.
This can also be accompanied by testing for human papillomavirus (HPV), the culprit virus in the development of cervical cancer. It can take 3-7 years for high-grade changes in the cervical cells to become cancer, underlying the importance of screening in disease prevention.
During a Pap smear, the cervix is accessed via insertion from a speculum into the vagina for adequate visualization. The cells are then sampled with either a brush or alternative instrument, and subsequently placed in a preparatory solution for laboratory testing.
General screening recommendations per the American College of Obstetricians and Gynecologist are as follows:
- Women aged 21-29 years should have a Pap test alone performed every 3 years. HPV testing is not recommended
- Women aged 30-65 years should have a Pap test and an HPV test (co-testing) every 5 years. It is also acceptable to have a Pap test alone every 3 years.
- For those women who have undergone a hysterectomy, screening may still be applicable in the following circumstances:
- If the cervix was not removed
- If the cervix was removed in the setting of cervical cancer/cervical changes, in which case abnormal cells can still be present at the top of the vagina.
This should be followed in the event of an abnormal screening test to distinguish between high-grade changes or frank cancer. Colposcopy or cervical biopsy can be performed, and this should be undertaken via a Gynecologist, with further recommendations to follow thereafter.
COLORECTAL CANCER SCREENING
Colorectal cancer (CRC) is the fourth most frequently diagnosed cancer in the U.S. An estimated 101,420 new cases of colon cancer and 44,180 new cases of rectal cancer will be diagnosed in the U.S. in 2019. During this time frame an estimated 51,020 people will die from this disease (4).
Screening allows detection of cancer at an early, curable stage and can allay the mortality associated with CRC. Moreover, it can facilitate identification and removal of polyps, thus reducing the incidence of CRC (5).
The National Comprehensive Cancer Network (NCCN) stratifies persons based on their risk profile, and then based on this, offers corresponding screening guidelines. Persons at higher risk include:
- a personal history of adenomas
- sessile serrated polyps
- inflammatory bowel disease (such as ulcerative colitis, or Crohn’s disease)
- previous colorectal cancer and
- a positive family history
Furthermore, certain familial syndromes confer a higher risk, and mandate more stringent/frequent screening algorithms.
As it stands, screening is generally classified as either structural tests or stool/fecal-based tests (6).
Structural Screening Tests:
1) COLONOSCOPY: This is considered the gold standard for CRC screening, and is recommend on at least 10-yearly intervals, commencing at age 50 years old, for average risk persons. Depending on the type, size and number of polyps found at examination, scoping may be repeated at shorter intervals.
2) FLEXIBLE SIGMOIDOSCOPY: In this procedure, the portion of the colon up to the sigmoid is evaluated. There is benefit to this procedure in significantly reducing the incidence and mortality of CRC, but it seems confined mainly to distal CRC, rather than to lesions higher-up when compared to traditional colonoscopy (7).
3) COMPUTED TOMOGRAPHIC COLONOGRAPHY: CT colonography, also referred to as virtual colonoscopy, uses CT imaging to detect colonic masses. A formal colonoscopy is required for biopsy/resection if a suspicious lesion is detected.
Fecal-based screening tests detect occult blood or alterations in shed DNA from stool. They are as follows:
1) FECAL OCCULT BLOOD TEST: The stool sample that is provided is tested for the presence of blood which is not obviously apparent. This is recommended annually, or every three (3) years if combined with flexible sigmoidoscopy.
2 FIT-DNA-BASED or MULTI-TARGET STOOL DNA TEST: This screens for the presence of known DNA changes associated with the development of CRC, which is sloughed into the stool. It also checks for occult blood. The FDA recommends screening every three (3) years.
Invasive procedures can often be performed by the General Surgeon or Gastroenterologist, whereas fecal testing can be accomplished at the Primary Care office.
Cancer Screening for Cancer Prevention
Many of us are intimately involved with cancer, either being personally diagnosed or having a loved one afflicted with this ailment. While others have been more peripherally acquainted this disease, whether it’s our neighbor, work-colleague or grocer who has been diagnosed.
Nonetheless, we all know that cancer exists, it does not discriminate, and the repercussions of diagnosis are far-reaching. As such, we continue to advocate public education and awareness.
This concludes our cancer screening update for this edition. In subsequent segments, we will include screening protocols for other malignancies, such as lung cancer and prostate cancer. In the meantime, we strongly advocate that you follow up with your local primary care provider to initiate these cancer-specific screening protocols.
And, as the old adage attests:
“An ounce of prevention is better that a ton of cure.”
- National Cancer Institute. Understanding Cancer, Cancer Statistics. April 2018.
- American Cancer Society. Breast Cancer Facts and Figures 2009-2010. Atlanta: American Cancer Society
- Siegel RL, Miller KD, Jemal A. Cancer Statistics, 2017. CA Cancer J Clin 2017;67:7-30. Siegel RL, Miller KD, Jemal A. Cancer Statisitics, 2018. CA Cancer J Clin 2018;68:7-30
- Siegel RL, Miller KD, Jemal A. Cancer Statistics, 2018. CA Cancer J Clin 2019;6:7-34
- USPSTF. Screening for colorectal cancer: US Preventive Services Task Force recommendation statement. Ann Intern Med 2008; 149:637-637
- Burt RW. Colorectal cancer screening. Curr opin Gastroenterol 2010;26:466-470.
- Wang YR, Cangemi JR, Loftus EV, et al. Risk of colorectal cancer after colonoscopy compared with flexible sigmoidoscopy or no lower endoscopy among older patients in the United States, 1985-2005. Mayo Clinic Proc 2013;88:464-470