According to the World Health Organization (WHO), cancer is a leading cause of death worldwide, “accounting for nearly 10 million deaths in 2020, or nearly one in six deaths.” Some of the most common cancers include breast, colorectal, lung, liver, stomach, and skin. “Each year, approximately 400 000 children develop cancer. The most common cancers vary between countries. Cervical cancer is the most common in 23 countries,” it further added.
While a healthy diet, exercise, sleep schedule, and certain lifestyle habits can lower the risk of cancer, have you ever heard about chemoprevention, or the use of certain drugs aimed at the goal of prevention or reversing the development of cancer. Worry not if you don’t; we are here to tell you all about it.
What is chemoprevention?
“Chemoprevention is the use of certain medicines, vitamins or supplements that help to reduce the risk of developing cancer or prevent it from recurring. For chemoprevention to be feasible, a high-risk population needs to be identified and an effective chemoprevention medication with minimal side effects should be available,” Dr. Nikhil S Ghadyalpatil, Senior Consultant Medical Oncologist and Hemato-Oncologist, Yashoda Hospitals Hyderabad, told indianexpress.com.
However, the expert added that chemoprevention can also be administered to healthy individuals to reduce their risk of getting cancer. “This is called primary chemoprevention. On the other hand, secondary chemoprevention is given to prevent a precancerous area from becoming cancerous in high-risk individuals, and tertiary chemoprevention helps prevent the recurrence of cancer in individuals who have received treatment earlier,” he explained.
But what are the medicines or foods used for chemoprevention?
Experts explain that a large number of natural and synthetic compounds with anti-cancer properties can be classified as chemopreventive based on their mechanism of action or chemical structure. Dr Vijay Patil, Consultant (Medical Oncology) at PD Hinduja Hospital and Medical Research Centre, Khar, added, “The classes of chemopreventive agents are classified in accordance with their sources, such as hormonal, medications, diet-related agents, and vaccines”.
Adding, Dr Harshit Shah, Associate Consultant-Surgical Oncology, Fortis Hospital Kalyan said that diet-derived natural products with limited chemo-preventive activity include turmeric, grapes, mulberries, peanuts, green tea extract, fish oil, black raspberries, or strawberries. “Epidemiologic studies suggest that diets high in calcium lower colon cancer risk as calcium binds bile and fatty acids, which cause proliferation of colonic epithelium. It is hypothesised that calcium reduces intraluminal exposure to these compounds. The randomised controlled ‘Calcium Polyp Prevention Study’ found that calcium supplementation decreased the absolute risk of Adenomatous Polyp recurrence by 12 percent at 5 years”, he explained.
However, he was quick to add that in the Women’s Health Initiative, “combined use of calcium carbonate and vitamin D twice daily did not reduce the incidence of invasive colorectal cancer compared with placebo after seven years”.
Can cancer vaccinations help?
While there are a variety of cancers, there are only two vaccines: one for hepatitis B virus which is a leading cause of liver cancer, and another for human papillomavirus (HPV), which leads to cervical cancer.
According to WHO, cancer-causing infections, HPV and hepatitis, are responsible for approximately 30 per cent of cancer cases in low-and lower-middle-income countries. However, they can be easily prevented as vaccines available for them are highly effective. The Hepatitis B vaccine “offers 98 per cent to 100 per cent protection against hepatitis B,” the United Nations agency stated.
Similarly, cervical cancer is the fourth most common cancer among women globally and can easily be prevented if a vaccine is administered at the right age. “About 90 per cent of the new cases and deaths worldwide (from cervical cancer) in 2020 occurred in low-and middle-income countries,” it informed.
According to the Centre for Disease Control, all HPV vaccines have been found to have high efficacy (close to 100%) for the prevention of HPV vaccine type-related persistent infection, cervical intraepithelial neoplasia (CIN) 2/3, and adenocarcinoma in situ (AIS) in clinical trials.
Cervical cancer vaccine should ideally be administered to girls “as young as 9 years as well as in those aged 13–26 years who have not previously completed vaccination,” according to the National Center for Biotechnology Information. It is done so that the females have immunity against HPV infection before they become sexually active, as you can get HPV from having unprotected sex.
“We have seen that more than 95 per cent chances of decreasing the incidence of premalignant lesions in those females who have not acquired HPV infection,” said Dr Shah, added that if the vaccine is taken after exposure to HPV infection, while its efficacy gets reduced, it is still there. “HPV infection can occur at a very early age and the efficacy of the vaccine to prevent this premalignant lesion is approximately 40 to 45 per cent in the over all population including even those who have acquired HPV infection even during the administration of the vaccine,” explained Dr Shah.
Primary chemoprevention
If you are a healthy individual, there are certain things that you can do to prevent the chances of getting cancer. It starts with making dietary and lifestyle changes. According to WHO, a 30 to 40 per cent cancer burden can be attributed to lifestyle risk factors such as tobacco smoking, alcohol consumption, a diet low in fruit and vegetables, being overweight and obese, and physical inactivity.
“Primary prevention includes risk factor modification like cessation of tobacco, smoking, sun exposure, dietary modification – decreased meat consumptions, limiting fatty foods, packed and processed foods and alcohol. Also, it is important to increase the intake of dietary fibres, fruits, and vegetables along with moderate physical activity for at least 30 minutes for five or more days a week,” advised Dr Pooja Babbar, consultant, medical Oncology, CK Birla Hospital, Gurugram.
Secondary and Tertiary chemoprevention
Medications like aspirin, statin, and metformin, and supplements like carotenoids, folic acid, calcium, selenium and flavonoids are used for chemoprevention. Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) have shown to lower the risk of cancer in certain disease groups.
“Cell damage can be avoided with the aid of antioxidant supplements such the CO enzyme Q10, selenium, and the vitamins A, C, and E,” said Dr B Sainath, Consultant Medical and Paediatric Oncologist, CARE Hospitals Banjara hills, Hyderabad.
Adding that oral contraceptive pills are effective in reducing the risk of developing ovarian cancer, Dr Sainath told indianexpress.com: “The use of oral contraceptives during the past three decades has led to a dramatic decline in the incidence of cancers of the ovary and endometrium. However, there is marginal risk in the increase of breast cancer which goes away after discontinuation after two to three years”.
In a similar vein, the National Cancer Institute stated, “A reduction in ovarian cancer risk with the use of oral contraceptives is also seen among women who carry a harmful mutation in the BRCA1 or BRCA2 gene”.
However, chemopreventive medications are prescribed by doctors after examining a patient’s medical history and risk factors.
Who can take chemopreventive medications?
While it is recommended that everyone make lifestyle and dietary changes and get vaccinated against Hepatitis B, and HPV infection, it is not the same for chemopreventive drugs. They should and must only be taken only after a doctor prescribes them.
“The benefits of chemoprevention may be in preventing the development of malignancies. However, these medications come with certain associated risks – like Tamoxifen can be associated with blood clot formation. Also, patients taking aspirin may be at risk of bleeding, especially at the age of 70 or more. Also, dosage and duration of Aspirin are important but is still debatable,” cautioned Dr Pritam Kataria, Consultant, Department of Medical Oncology at Sir HN Reliance Foundation Hospital and Research Centre, Mumbai.
Chemoprevention for breast cancer (in high-risk individuals)
“Chemoprevention is more prevalent in breast cancer as compared to any other cancer,” said Dr Patil, adding that “Tamoxifen and Raloxifene drugs have shown to lower the risk of breast cancer. They are most effective in lowering the risk of estrogen receptor-positive breast cancer. Tamoxifen blocks the effects of estrogen on tumour growth. It lowers the risk of breast cancer recurrence as well. Raloxifene has been seen to exhibit similar action to tamoxifen in women who have gone through menopause”.
Dr Shah agreed and said, “Medications like Tamoxifen and Raloxifene have been approved by the U.S. Food and Drug Administration for reduction of breast cancer in women. The International Breast Cancer Intervention Study (IBIS-I), NSABP P1 trial and the Italian Randomized Tamoxifen Prevention Trial demonstrated a reduction in Breast Cancer incidence with Tamoxifen use by approximately 49 percent in high-risk women. However, a small increase in risk of endometrial cancer, stroke, pulmonary emboli and deep vein thrombosis was noted”.
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