Dr. Ayekpam Anil Meetei
Non-communicable diseases now account for the majority of global deaths. According to the World Health Organization estimate, it is the second leading cause of death in the world. The incidence of cancer and deaths is growing rapidly worldwide due to aging and population growth, along with changes in the incidence and distribution of the major risk factors for cancer, including developmental factors socio-economic. The GLOBOCAN 2018 report estimates, there were an estimated 181 lakh new cancers diagnosed and 96 lakhs cancer deaths in the year 2018. 10 most common cancers worldwide in decreasing order are Lung, Breast, Colorectal, Prostate, stomach, liver, esophagus, cervix, thyroid and Urine Bladder. Early diagnosis and treatment of cancers is one strategy to reduce cancer deaths.
Cancer screening refers to performing a test or examination on an asymptomatic individual. Screening is an initial test that must be followed by more investigations / tests to detect a disease in question. Cancer screening aims to prevent death and suffering from the disease in question through early therapeutic intervention. A distinction must be made between screening and diagnosis, where a patient’s complaint is investigated to find out the cause of the symptoms.
Four requirements for cancer screening must be met.
i. The cancer burden is considerable.
ii. The natural history of the disease means that a detectable preclinical period exists.
iii. A test or procedure must detect cancer earlier than if the cancers were detected as a result of the development of symptoms
iv. Earlier treatment initiated as a result of screening results is a better outcome.
These requirements are necessary but not sufficient for the test or procedure to be efficient. A screening test is effective when it results in a reduction in cancer-specific deaths. Common cancers that can be screened include breast, colon, cervical and lung cancers. Some patients with a genetic mutation may require specific cancer surveillance, for example, ovarian carcinoma surveillance in a patient with a BRCA mutation. The American Cancer Society (ACS) and the United States Prevention Services Task Force (USPSTF) are two organizations that publish widely used cancer screening guidelines, based on scientific evidence. The recommendations for screening common cancers are set out below:
Breast Cancer: Clinical Breast Audit (CBE) is an annual physical examination of the breast by trained medical staff. Breast Self-Audit (BSE) is a monthly self-examination of its own breast. CBE and BSE can detect cancers during the interval between mammographic screenings and are useful as complementary screening procedures. CBE and BSE alone are not recommended for breast cancer screening by ACS. Mammography is a low-dose breast X-ray and is the most effective screening method.
i) Annual mammography starting at age 41.
ii) After age 55, the patient can have a mammogram once in 2 years or continue screening every year.
In our health induction, screening once in 2 years starting at age 50, as recommended by USPSTF is a more reasonable option.
Colon Cancer Screening: Colorectal cancer screening involves either stool tests for blood or DNA associated with polyps or cancer or structural examination looking for polyps or early cancers. A fecal occult blood test (FOBT) is a simple test to detect blood present in stool, shed from cancers in the colon. Colonoscopy needs to investigate positive FOBT. Screening of colorectal cancer after the age of 45 is recommended. The options for screening for colorectal cancer are:
i) Annual FOBT
ii) Flexible sigmoidoscopy every 5 years
iii) Colonoscopy every 10 years
iv) CT Colonography every 5 years
Colonoscopy and Sigmoidoscopy are invasive methods for screening. Establishing us with limited health resources, an annual FOBT is the only viable option for mass screening.
Cervical Cancer Screening: Cervical cancer is the second most common cancer among Indian women. The most important cause of cervical cancer is infection with Human Papilloma Virus (HPV). Cervical cancer progresses in an orderly fashion with pre-invasive lesions developing before invasive cancerous lesions. It is one of the most suitable cancers for screening.
The PAP cervix is a simple test to collect a sample of a cell using a brush / spatula which is then examined for cancerous cells under a microscope. An HPV test uses a brush to collect cells and fluids from the cervix to check for the presence of human papilloma virus. Visual examination after cervical acetic acid (VIA) is a cheap and convenient method but is less accurate and is used in a resource-limited setting.
i) Age 25 – 65 years-HPV tested every 5 years (or)
– Pap smear every 3 years (or)
– HPV testing and PAP testing every 5 years
ii) After the age of 65, screening may be terminated with pre-documented negative screening in the 10-year period before 65 years.
A fluid-based biopsy uses a brush to collect cells and cervical fluids, which are then used for testing HPV and cancerous cells, can be performed as an OPD procedure.
Lung Cancer Screening: Smoking is the most important cause of lung cancer. A person who smokes 20 cigarette butts a day for one year is quoted as 1 pack year and for 2 years as 2 pack years. A person who smokes 40 cigarettes in a day for one year is quantified as 2 pack years and for 2 years as 4 pack years. Lung cancer screening is recommended for individuals who
i) Age 55 to 74 years
ii) At least 30 years of smoking year smoking history
iii) Currently smoking or quitting for the past 15 years
Low dose CT (LDCT) uses only 1 / 5th of the conventional Chest CT radiation dose and usually only takes about 15 seconds to screen. LDCT is the preferred method for screening Lung Cancer and Chest X-Rays are not recommended for Lung Cancer screening.
Cancer screening should be a public health intervention. Opportunistic screening is when a patient sees a healthcare provider who chooses to screen or not. European developed countries have been able to reduce deaths associated with these cancers by almost 20-30% with population screening. Screening is not without risks. A screening test may miss existing cancers and provide inaccurate assurance. Rapidly growing cancers can develop during periods of regular screening. He may also diagnose a non-cancerous lesion as cancerous. Some cancers may also be found that are not supposed to metastasize or cause harm in the life span of the particular patient, a term medically known as overdiagnosis. Overdiagnosis can occur in thyroid, prostrate, kidney, neuroblastoma and melanoma cancers. Cancer screening is an evolving science and will continue to evolve with better evidence from well-conducted trials. The above methods or procedures can be adapted according to patient risk factors. Screening for common cancers and preventative measures such as smoking cessation and vaccination will certainly have an impact on cancer deaths.
(The author is a Consultant Surgical Oncologist at Shija Hospitals and is MS (Gen. Surgery), DNB (Surgical Oncology))