PTC is the most common thyroid cancer (about 80% of all thyroid cancers). Most cases present as a painless nodule that is relatively firm. Sometimes it is found on an ultrasound or CT scan done for other reasons. The diagnosis is usually made by needle biopsy (FNA). Generally, PTC has a good prognosis.
Female sex, age under 45, small tumors (< 4cm) and tumors confined to the thyroid gland are favorable features. These tumors are generally consider a lower risk situation. Male sex, more advanced age, larger tumors(>4 cm) and tumors that invade into local tissues are more worrisome findings. These tumors are considered a little higher risk situation. Each case is individualized, but with surgery and when needed, radioactive iodine treatment, the vast majority of patients do well.
Surgery is the cornerstone of therapy and frequently curative. Signifcant PTC is most appropriately treated with total thyroidectomy. While the tumor is usually present on one side, small areas of cancer may be on the other side in 20%-30% of cases. Total removal of the thyroid gland is generally recommended. By removing the entire gland, treatment with radioactive iodine pills, to destroy any microscopic tumor cells, is greatly facilitated. Also by removing all thyroid tissue, a blood test (thyroglobulin level) can be used to detect recurrence. Thyroglobulin is made by thyroid tissue and by thyroid cancer cells. If all thyroid tissue is removed, then the thyroglobulin level should not be detectable. If the thyroglobulin level goes up after thyroid removal then the tumor could be back.
Recently, renewed interest in treating low risk tumors with only thyroid lobectomy has been generated by data base review studies. The argument for less surgery is that it is difficult to show a survival advantage with a total thyroidectomy compared to simple lobectomy for low risk tumors. With simple lobectomy there is the possibility of avoiding the need for thyroid replacement therapy. Also, the risk of permanent hypoparathyroidism is also avoided. However, leaving thyroid tissue in place prevents the detection of by using the thyroglobin tumor marker and radioactive iodine is not a therapeutic option post op. In the final analysis, it can be difficult to be certain of the risk of recurrence after therapy, preoperatively. What is agreed among all surgeons is that the best chance for cure is to remove all disease at the initial operation. Experienced, high volume surgeons can accomplish this with minimal additional risk and usually this is best accomplished with a total thyroidectomy. If your surgeon is less experienced or only occasionally performs thyroid surgery, then lobectomy alone might be a safer approach with a good chance of controlling the problem in low risk situations.
In 2015, The ATA (American Thyorid Association) released guidelines about surgical treatment of low risk PTC. For tumors less than 1 cm, simple lobectomy is generally recommended as long as there are no other factors that elevate risk of persistent or recurrent disease. For tumors between 1 and 4 cm, lobectomy may be considered definitive surgical therapy if there are no other adverse risk factors. Importantly, lobectomy is not recommended in this situation but may be considered.
To be considered for lobectomy in this setting, the tumor would need to be contained to the thyroid lobe based on ultrasound appearance, there should be no evidence of lymph node metastasis (by physical exam or ultrasound), no evidence of tumor contact with the trachea or esophagus on ultrasound, no nodules in the other thyroid lobe, no personal history of significant head and neck radiation exposure, and no family history of well differentiated thyroid cancer. These features can been assessed preop operatively.
Additional risk factors for recurrence include a microscopically positive edge (margin)where the thyroid is removed. Microscopic evidence that the tumor has grown beyond the covering (capsule) of the thyroid , or if there is microscopic evidence of tumor in near by lymph nodes ( lymph node metastasis ). These features will only be know after the final pathology report is available, usually a few days post op.
Unfortunately, up to 40% of patients thought to have low risk tumors during preop planning and are treated with thyroid lobectomy, will be found to have at least one high risk feature identified during surgery or on the final pathology report. Therefore, the possibility of a total throidctomy remains and a significant minority of patients may be advised to return to the operating room for a second operation to remove the other lobe if the features described above are realized only on the final pathology report.
Furthermore, the hope to avoid thyroid hormone therapy post op ( Sythroid) is often not achieved with lobectomy alone. Up to 25% of patients who undergo thyroid lobectomy for any reason will need some type of supplemental thyroid hormone support. After thyroid lobectomy for cancer, the patient’s TSH level will need to be kept under 2 to help minimize the risk of growth of any unsuspected residual microscopic tumor. To achieve this, an even higher percntage of patients will need to go on thyroid replacement medication to suppress their TSH level appropriately. Therefore, avoiding total thyroidectomy in an effort to avoid thyroid replacement medication may not be achieved .
Another area of controversy is how to handle the surrounding lymph nodes. PTC may spread into surrounding lymph nodes in a significant number of cases. Generally, the larger the tumor the more likely node metastasis has occurred. It is difficult to show that lymph node metastasis always results in a bad out come for the patients, but most surgeons agree that it increases the risk that the tumor may come back in the neck and it may be associated with a higher mortality rate. Again it is difficult to prove this because people do so well with PTC in general. Our general approach is to recommend lymph node removal (dissection) in the central compartment of the neck (level 6) for patients with high risk papillary cancer . This is where most lymph node metastasis occur. We believe it gives patients the best chance of local control and cure. However, it is difficult to show scientifically that removal of grossly normal lymph nodes in patients with tumors less than 2 cm improves outcomes. Arguments against this approach are that it may increase the risk of complications. In experienced hands the additional risks are very small. The most common issue is prolonged (but still temporary) hypocalcemia.
Following treatment, suppressive therapy with thyroid replacement medication is the cornerstone of follow-up . In situations where the risk of recurrence is elevated, radioactive iodine may be recommended. This is usually given under the direction of an endocrinologist a few weeks after surgery. Total body scanning may be done with it to check for evidence of spread of the disease. The idea behind RAI is that in the absence of normal thyroid tissue, any microscopic thyroid cancer cells will take up the radioactive iodine and be destroyed. After treatment, most patients are followed by the endocrinologist. Periodic exams, thyroglobulin levels and neck ultrasounds are done to watch for recurrence.