Head and Neck cancer -13-Thyroid
HEAD & NECK CANCER PART-13
(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)
Question: Thank you Chiragbhai for explaining details about Cancer of Unknown Primary, very interesting category, and salivary gland tumors. Can you tell us something about thyroid cancers now? They seem to be on the rise.
Ans: Thyroid cancer is one of the most common tumor in head and neck region. There is a significant rise in incidence, however majority are very early stage tumors. It is not clear whether rise in incidence is due to early detection from more frequent medical visits and tests in general or a true rise. In large majority of cases, there is no known etiology. A small number of cases are associated with exposure to ionizing radiation in childhood (such as for treatment of pediatric cancers like Hodgkin, neuroblastoma, Wilm’s etc). Some are also associated with exposure to nuclear reactor accident or other such sources.
Majority of these cancers are well differentiated. Major histologic types include Follicular, Papillary, Mixed, Anaplastic, Hurthle cell, and Medullary Thyroid Cancer. Last three constitute about 10% only.
Que: So how do you suspect thyroid cancer, and is there a test for early diagnosis or screening?
Ans: Fortunately, most such cancers are detected incidentally, as part of health check up or during work up for some other illness. They present as single painless thyroid nodule in most cases. Aggressive tumors frequently present with symptoms mainly due to local invasion or pain and neck nodes. Diagnosis involves a neck sonography and FNAC (fine needle aspiration biopsy). These tests are generally sufficient. Special scans like radioactive iodine scan is not required for diagnosis. Many malignant tumors are also “cold” i.e. nonfunctional on such scans, hence they are not useful in early decision making.
Serum calcitonin levels and CEA are useful in suspected medullary thyroid cancer. In diagnosed cases, especially if familial or associated with some cancer types in family, one should test for presence of RET mutation.
Que: How are they treated?
Ans: Surgery is the mainstay of treatment, and in vast majority, it is the only treatment required. Total thyroidectomy is the most common surgery. For very low risk tumors, such as less than 1 cm solitary nodule, a hemi thyroidectomy may be considered. Total thyroidectomy should be performed only by experienced surgeon and in a hospital with good ICU support, as occasionally there may be severe hypocalcemia or recurrent laryngeal nerve injury.
Most experts recommend a dose of radioactive iodine post operatively to treat possible occult metastases, and to ablate any remnant thyroid (which helps in follow up testing). Thyroid hormone supplement should be given postoperatively to prevent hypothyroidism and hence high TSH. This is important as TSH can lead to growth of any remaining cancer cells.
Radiotherapy is used only in palliation of advance cases. Same is true for chemotherapy, as most agents have very limited efficacy.
For medullary thyroid cancer, it is important to screen family for RET gene mutation (if positive in patient). All family members with this mutation should undergo prophylactic total thyroidectomy. A number of these patients are already found to have cancer in histopathology examination.
Que: What is the prognosis, and how do you treat recurrent disease?
Ans: Prognosis is excellent in most cases except anaplastic thyroid cancer. Patients older than 40-50 years have a somewhat less success rate in long term, compared with younger patients. Local recurrence is treated with surgery. Metastatic disease is treated by radioactive iodine. About 50% of patients achieve long term disease control even in stage 4 i.e. after distant spread, with a course of radioactive iodine. Patients who have resistant disease, chemotherapy or more frequently nowadays targeted therapy is used. Doxorubicin was the agent used most commonly, but with only about 25% response rate.
Two new medicines were recently approved for medullary thyroid cancer – vandetanib, and cabozantinib – Both tyrosine kinase inhibitors.
Sorafenib and sunitinib also are tyrosine kinase inhibitors that work in a variety of thyroid cancers, for palliation. Lenvatinib is also a tyrosine kinase inhibitor approved for use in palliation of differentiated thyroid cancers. Response rate is about 50-70% for these agents, much better than chemotherapy, and are also oral agents. Thus they are also more convenient.
January 9th 2015.
Dr. Chirag A. Shah; M.D. Oncology/Hematology (USA), 079 26754001. Diplomate American Board of Oncology and Hematology. Ahmedabad. email@example.com Shyam Hem-Onc Clinic. 402 Galaxy, Near Shivranjani, Opp Jhansi ki Rani BRTS, Ahmedabad. www.shyamhemoncclinic.com