Thyroid cancer: why chemotherapy is rarely needed

Chemotherapy is rarely used for thyroid cancer. The most common types, papillary and follicular thyroid cancer, are usually treated with surgery to remove part or all of the thyroid gland, often followed by radioactive iodine treatment and thyroid hormone tablets. Medullary thyroid cancer is treated mainly with surgery, and with targeted tablets if it has spread. Chemotherapy is mostly reserved for anaplastic thyroid cancer, a rare and fast-growing type, where it may be given together with radiotherapy, and occasionally for other thyroid cancers that keep growing after standard treatments. If you have been told you have thyroid cancer and are worried about chemotherapy, it is worth asking your team directly whether it is part of your plan at all.

Radioactive iodine is used instead of chemotherapy for many thyroid cancers because thyroid cells naturally absorb iodine from the blood, and most papillary and follicular cancer cells keep this ability. When radioactive iodine is swallowed as a capsule or liquid, it is taken up mainly by thyroid tissue and thyroid cancer cells wherever they are in the body, delivering radiation directly to them while largely sparing other organs. Standard chemotherapy medicines, by contrast, generally do not work well against these slow-growing thyroid cancers. Radioactive iodine does not help medullary or anaplastic thyroid cancer, because those cells do not absorb iodine, which is why they are treated in quite different ways by the team.

Chemotherapy or other medicines become necessary in a small number of situations: anaplastic thyroid cancer; cancers that have spread and no longer absorb radioactive iodine; and cancers that keep growing or causing problems despite surgery, radioactive iodine and radiotherapy. Even then, targeted tablets chosen after genetic tests on the tumour tissue are now used far more often than traditional chemotherapy medicines. An endocrine surgeon, endocrinologist, nuclear medicine specialist and medical or radiation oncologist often work together as one team to plan care. This page explains the general picture and cannot describe your own plan. Your team will explain which treatments you need and why, and how your follow-up blood tests and scans will be arranged.

Rarely used

Most thyroid cancers never need chemotherapy.

Radioactive iodine instead

Thyroid cancer cells absorb iodine, so treatment reaches them directly.

Needed in specific cases

Mainly anaplastic cancer or cancers that stop responding.

It cannot tell you which treatments you need. That depends on the type of thyroid cancer, its spread and your tests.

It also cannot predict how you will respond. Your endocrinologist and oncologist can explain your own results.

Thyroid hormone tablets

After the thyroid is removed, thyroid hormone tablets replace what the gland used to make and may also help keep some cancers from growing. They are usually taken for life. Never stop or change them on your own. Your doctor adjusts them based on regular blood tests and how you feel.

The low-iodine diet

For a short period before radioactive iodine, you may be asked to avoid iodised salt, seafood, dairy products, egg yolks and some processed foods. This helps thyroid cells take up more of the treatment. Your team will give you a food list suited to Indian cooking and explain when to start.

Radiation safety at home

After radioactive iodine, small amounts of radiation leave the body in saliva, sweat and urine. For a short time you may be asked to sleep alone, avoid close contact with children and pregnant women, use separate utensils and flush the toilet twice. The unit gives written instructions.

Effects of radioactive iodine

Most people feel well, but some notice a sore or swollen neck, dry mouth, taste changes or swelling of the salivary glands. Sucking sour sweets and drinking plenty of water, as advised by your team, may help. Rarely, repeated treatments can affect blood counts or fertility.

When radioactive iodine stops working

Some thyroid cancers gradually lose their ability to absorb iodine. Further radioactive iodine is then unlikely to help. Your team may suggest monitoring if the cancer is growing slowly, or targeted tablets, surgery or radiotherapy for areas that are growing or causing troublesome symptoms such as pain.

Targeted tablets

Targeted tablets block signals that help thyroid cancer cells grow. Some are chosen after genetic tests on the tumour. They can cause high blood pressure, loose motions, tiredness, skin changes on the hands and feet and weight loss, so regular checks with your oncologist are needed throughout.

Medullary cancer and families

Some medullary thyroid cancers run in families because of an inherited gene change. Genetic testing is usually offered, and close relatives may be tested too. Children who carry the gene change may be advised to have the thyroid removed early to prevent cancer developing later in life.

Anaplastic thyroid cancer

Anaplastic thyroid cancer grows very quickly and needs urgent specialist care. Tissue tests for genetic changes are done rapidly, because targeted treatment may help some people. Chemotherapy and radiotherapy may be combined, and care for breathing, swallowing, nutrition and comfort is planned alongside from the very start.

Blood tests in follow-up

After treatment for papillary or follicular cancer, a blood test called thyroglobulin is used to watch for the cancer coming back, because only thyroid tissue makes it. For medullary cancer, calcitonin and another blood marker are used. Your team will explain how often these are checked.

Neck ultrasound and scans

Regular neck ultrasound scans check the area where the thyroid was and the glands in the neck. Iodine scans, CT scans or PET-CT scans may be added if blood tests rise. Bring previous reports to each visit, so changes can be compared accurately and carefully over time.

Pregnancy and fertility

Women should not be pregnant or breastfeeding during radioactive iodine treatment, and are usually advised to wait several months afterwards before trying for a baby. Men may be advised to wait too. Tell your team about pregnancy plans before treatment, so timing can be discussed properly.

Calcium after surgery

Surgery can affect the small glands that control calcium, which sit next to the thyroid. Low calcium causes tingling and cramps, usually in the first days. Calcium and vitamin D tablets may be needed for a while, or sometimes for longer, with regular blood tests to guide how much is needed.

What to do next

Ask your team which type of thyroid cancer you have, whether radioactive iodine is planned, whether chemotherapy or targeted tablets will ever be needed, and how follow-up blood tests and scans will be arranged.