The most prominent cause of thyroid gland cancer is the exposure to radiation in childhood. This is a huge concern in the West, though not so much in India
Cancer of the thyroid gland is uncommon; it accounts for only three per cent of all new cancer cases in the world, but its incidence is increasing rapidly. A large part of this is due to better and quicker diagnostic tools which can now detect cancer cells that were missed earlier. Yet, scientists are confused about the exact cause for the rapid rise in thyroid cancer cases. In the US, the number of people diagnosed with this disease has increased to 70,000 per year, that is up from 12,000 in the year 2000, an almost six-fold rise. The prevalence of thyroid cancer in whole world is about one million persons.
According to the Cancer Prevention Institute of California, the rate of thyroid cancer in women doubled between 1990 and 2005. It is now the 5th most common cancer in women. Its researchers say — they have been seeing an average of five to six per cent annual increase in cases of thyroid cancer in both men and women, calling it an epidemic. There is an absence of reliable statistics for India, but it is estimated that about 12,000 to 20,000 Indians are diagnosed with the disease each year.
Women are especially at risk, probably due to hormonal changes related to the reproductive system. Three times more women in the world suffer from thyroid cancer compared to men. For India, the ratio is narrower at 2:1. Indians are also becoming victims of the disease when quite young. The average age of a thyroid cancer patient in India is 20 to 30 years, compared to 50 to 60 years in the West. However, it is rarely found in children.
The thyroid gland is a small gland at the base of the neck, located on either side of the windpipe below the Adam's apple. It releases hormones to regulate the body's metabolic rate and to control the level of calcium in the blood.The exact cause of thyroid cancer remains unknown, but there are several risk factors which increase its likelihood. The most prominent is exposure to radiation in childhood, particularly before the age of five. This, however, is a huge concern in the West, not in India. Inherited genetic conditions constitute another factor.
Thyroid cancer grows very slowly. People may carry it for years before the symptoms appear, and a diagnosis normally made after needle aspiration cytology test. Most patients approaching a doctor for treatment in India are in stage three or four when the cancer is highly advanced. Very few get to know about their cancer in the initial stages.
Fortunately, even if thyroid cancer is diagnosed late, the mortality rate is not very high. Overall,with appropriate treatment about 95 per cent of the patients go on to lead a normal life. The key is early diagnosis and treatment, but this is difficult due to the lack of awareness among the masses about thyroid cancer.
Most cases of thyroid cancer can be effectively cured with thyroidectomy (removal of thyroid gland by surgery) and Radioactive iodine treatment. As the removal of the thyroid gland deprives a patient of thyroid hormone, which is an important hormone for day-to-day running of your life, thyroid hormone replacement/suppression is essential for rest of the life depending on the stage of the disease. Regular blood tests are done to check the level of this hormone in the body and arrive at the correct dosage for the patient. Thyroid cancer patients must remember to check up with their doctor once a year with blood tests and to take medication for life.
(The writer is Professor & Head, Department of Nuclear Medicine, All India Institute of Medical Sciences)