Prevention of Cancer PART – 17
(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)
Question: In last part, we discussed some very important points 1. Fried foods – repeated use of same oil, as it is done in restaurants/street foods is unsafe. Higher amount of carcinogens. 2. Radon gas, a form of indoor air pollution, is associated with lung cancer. 3. Air and water pollution as a reason for cancer. 4. Solar radiation (UV rays) as a risk factor for skin cancers. Younger the age of exposure, higher the risk i.e. intense or prolonged exposure, sunburn. Artificial UV rays as in tanning bed also increase risk. 5. Medical use of radiation i.e. radiotherapy especially in children increases risk of cancer in long term. Similarly exposure to radiology studies frequently e.g. CT scan, PET scan etc increase risk. Again more risk in children.
Many of these points are under our control to some extent. And it is important to try and reduce exposure.
Ans: Yes, few radiology studies do not matter but many studies increase risk by a small percentage. Medical need of these studies should be balanced against long term risks. In emergency or acute setting, all required radiology studies should be done. But for follow up or non emergencies, avoid or replace with sonography or MRI if suitable.
Que: Thank you. What other important points our readers should know about Prevention of Cancer?
Ans: While we have spoken about lifestyle at great length, there are some measures available in modern medicine that can be considered for cancer prevention. Such as Vaccines, Medicines, Surgery. We have covered vaccines in our earlier series on cervical cancer and others. But we will summarize important points here. As we have learned earlier, infections can lead to cancer. Against some of these infections, we do have vaccines.
- HPV – Human Papilloma Virus. Most common infection leading to cancer. Mainly cancer of cervix, and some oral cancers. Vaccine against HPV is preferably given at a very young age. Between 9 to 14, two doses given about six months apart. If after age 14, up to about 45, then three doses are required – at 0, 2, 6 months. Upper age limit is not well defined. Vaccine leads to about 90% reduction in risk of HPV infection by major serotypes. And about 70% reduction in cancer. Age below 14 showed significantly higher benefit. This vaccine is also recommended for boys in Western world, to reduce risk of oral and anal cancers and genital warts. India’s national vaccination program has now included this vaccine for girls age 9-14, since January 2023, being rolled out phase wise in various states. An Indian vaccine has been launched with much less cost.
- Hepatitis B – This infection is a major cause of liver cancer worldwide. Vaccine against Hepatitis B has been part of national vaccination program in India for a long time. Adults today however are generally not vaccinated, as this development is of last few decades. Adults should consider testing for hepatitis B and if negative, to get vaccinated. For those in medical profession, this is extremely important, as the exposure risk is very high. I received this vaccine during my MBBS training, thanks to advice of a senior doctor. It was not part of childhood vaccination program until late 1990s.
Que: Thank you for this summary and some recent updates re HPV vaccine. Also, hepatitis B related information is especially important for healthcare professionals. What about role of medicines for prevention?
Ans: As we have medicines for treatment, there has been extensive research about use of medicines for cancer prevention. However with much less results, compared to vaccines or surgery.
Most notable perhaps is use of tamoxifen for reducing risk of breast cancer in those women at high risk, based on certain criteria. Tamoxifen given to these women for 5 years leads to reduction of breast cancer risk. But again, this is not for general population.
Aspirin and other NSAIDs have been studied extensively in multiple trials, meta analyses. There is no good conclusion about improvement in mortality. More likely no mortality benefit. Some benefit possibly in reducing risk of colon cancer. However due to lack of conclusive benefit, it is not recommended for general population for cancer prevention. Certain high risk patients with genetic syndromes e.g. Lynch may benefit from taking one aspirin daily. But these are rare patients. For general population, risks of taking daily aspirin for decades outweighs benefits.
Few other medicines have also been studied e.g. metformin. But none has been conclusive enough and hence not recommended by any major society or guidelines for cancer prevention.
Que: Oh! So no medicine has been able to provide this breakthrough. But what about vitamins, and other supplements? Do they prevent cancer?
Ans: Short answer is NO. Multiple studies have shown no benefit, and even harm in some cases. Nothing more than a simple multivitamin is recommended. That too if diet is not good or documented deficiency. High doses, as available in many commercial preparations are not recommended. Many such preparations are very popular in developed countries as well. In spite of clear recommendations from official government agencies and professional medical organizations against routine use. It is better to encourage people to have a healthy diet in general.
May 4, 2023 Dr Chirag A. Shah; M.D. Oncology/Hematology (USA), 9998084001.
Diplomate American Board of Oncology and Hematology. Ahmedabad. email@example.com