Thyroid surgery has been changing during the last few years, moving towards a parenchyma-sparing idea. It is true that thyroid cancer numbers raised in the past decades, but primarily because of the vast number of exams patients are now being offered. This has promoted over-diagnosis and over-treatment of “low-risk” differentiated thyroid cancers (DTCs). Is a less aggressive/parenchyma-sparing surgery the answer?
Classically, DTCs > 1cm are treated with total thyroidectomy (TT). However, the best treatment for DTCs with 1-4 cm without high-risk factors (incomplete resection, extrathyroidal extension, nodal disease, distant metastasis) is not consensual. New guidelines are now bringing into the decision-making process the possibility of doing less than total thyroidectomy. ATA guidelines promote a total thyroidectomy for DTC > 4 cm as the initial treatment, but for tumors 1-4 cm without any high-risk features a hemithyroidectomy (HT) might be offered. If any of those features are present, a total thyroidectomy must be performed.
Guidelines cannot be blindly followed, as they are not sure of what they are saying about those non-high-risk DTCs. A recent retrospective analysis of 4771 patients (1997-2020) with non-high-risk DTCs was conducted by Xiaodong Liu from Hong Kong, China, and published in BJS in December 2022. A comparison was conducted between TT and HT. Patients submitted to completion thyroidectomy within 1 year after HT were included in the TT group. Patients submitted to completion thyroidectomy beyond 1 year were considered a recurrence. Additionally, the authors excluded patients with previous thyroid treatments, clinically evident nodal disease, distant metastasis before surgery or within one year, < 18 yo.
A TT was performed in 71.3% of patients, while the remaining 28.7% underwent HT. Patients were operated on in 44 different hospitals. They found no differences in postoperative hematoma rate nor in unilateral recurrent laryngeal nerve (RLN) injury rate. As expected, there was no transient nor permanent hypoparathyroidism in the HT group, while after TT transient and permanent hypoparathyroidism occurred in 14.96% and 7.49% of cases, respectively. The most important results are coming next. While the cumulative incidence of overall death and cumulative incidence of disease-specific death were similar between TT and HT, the cumulative incidence of recurrence was significantly lower after TT (1.94% vs 4.97%). These results were also observed at 5y and 10 y follow-ups. A TT was associated with a lower incidence rate of recurrence compared to HT (1.78 vs 5.06 per 1000 person-years). According to the authors, “a better recurrence-free survival (p<0.001) was observed in patients who underwent TT” for non-high-risk DTCs. I would like to highlight that in the specific group of patients with < 55yo, a TT was also associated with better disease-specific survival. This probably supports the idea that for younger patients an aggressive surgery is better.
According to the authors, previous studies showing no difference in overall survival between TT and HT did not focus on disease recurrence. In that setting, it might be dangerous to use those data to support the decision to move toward thyroid parenchyma-sparing surgery. Although several papers reported similar overall survival and disease-specific survival between TT and HT, other studies suggested that HT has a higher risk of recurrence for DTCs (for both < 1 cm and > 1 cm). Other authors concluded that TT was associated with a lower risk of recurrence and better survival than HT for papillary thyroid cancer (PTC) > 1 cm. Although all these studies support the findings of Xiaodong et al, other authors present similar recurrence-free survival among patients with DTCs treated with TT or HT. Why is that so? What differentiates those studies? The definition of recurrence is the difference. Xiaodong diagnosed recurrence with biopsy, node removal, or neck dissection, but other studies did not. This might be responsible for the opposite results.
As Xiaodong et al say, the ideal treatment must “offer the best disease control and survival outcomes without compromising safety concerns”. In this setting, we must address postoperative hypocalcemia, for which TT is an independent risk factor. While transient hypoparathyroidism can be easily controlled, permanent hypocalcemia may lead ultimately to Fahr’s syndrome (read "Thyroid surgery can cause Fahr's syndrome"). How about RLN injury? According to the authors, unilateral nerve injury is similar between TT and HT. However, different studies present TT with a higher risk of RLN injury.
It is not clear what is the best surgical option to treat patients with DTCs (1 – 4 cm) without high-risk factors. Some would say TT is the best option because of the lower incidence of recurrence, but possible complications must be taken into consideration. HT is being suggested by recent guidelines, but studies are not unanimous to support that decision. As patients younger than 55 years old had better disease-specific survival when submitted to TT, this might be the best treatment option in this group of patients even with the risk of hypocalcemia and Fahr’s syndrome (read "Thyroid surgery can cause Fahr's syndrome"). For older patients, the decision-making process must include a well-informed patient. Should an 80 yo patient diagnosed with a non-high-risk DTC (1-4cm) be offered a TT?
Medicine is not math, medicine is not black and white, and medicine is not a simple guideline or protocol. Medicine is science and art. Study, question, study again, learn, update, touch the patient, discuss with fellows, and talk to the patient. This is the only way to a better decision-making process.
Link to PubMed:
Xiaodong Liu, Carlos KH Wong, Wendy WL Chan, et al. Survival after hemithyroidectomy versus total thyroidectomy in non-high-risk differentiated thyroid cancer: population-based analysis. BJS Open 2022.
Dr. Carlos Eduardo Costa Almeida
General Surgeon