Patients with intermediate-risk papillary thyroid cancer and lymph node metastasis show no significant increase in tumor recurrence when undergoing lobectomy compared with a total thyroidectomy, new research shows.

“Results of this cohort study suggest that patients with ipsilateral clinical lateral neck metastasis (cN1b) papillary thyroid cancer who underwent lobectomy exhibited recurrence-free survival rates similar to those who underwent total thyroidectomy after controlling for major prognostic factors,” the authors conclude in the study published online in JAMA Surgery.

“These findings suggest that cN1b alone should not be an absolute indication for total thyroidectomy,” they note.

The study, involving the largest cohort to date to compare patients with intermediate-risk papillary thyroid cancer treated with lobectomy versus total thyroidectomy, “challenged the current guidelines and pushed the boundary of limited surgical treatment even further,” say Michelle B. Mulder, MD, and Quan-Yang Duh, MD, of the Department of Surgery, University of California, San Francisco, in an accompanying editorial.

“It can be a game changer if confirmed by future prospective and multicenter studies,” they add.

Guidelines Still Recommend Total Thyroidectomy With Subsequent RAI

While lower-intensity treatment options, with a lower risk of complications, have gained favor in the treatment of low-risk papillary thyroid cancer, guidelines still recommend the consideration of total thyroidectomy and subsequent radioactive iodine ablation (RAI) for intermediate-risk cancers due to the higher chance of recurrence, particularly among those with clinically positive nodes.

However, data on the superiority of a total thyroidectomy, with or without RAI, versus lobectomy is inconsistent, prompting first author Siyuan Xu, MD, of the Department of Head and Neck Surgical Oncology, National Cancer Center, Beijing, China, and colleagues to compare the risk of recurrence with the two approaches.

For the study, patients with intermediate-risk papillary thyroid cancer treated at the Chinese Academy of Medical Sciences Cancer Hospital in Beijing between January 2000 and December 2017, who had a lobectomy or total thyroidectomy, were paired 1:1 in a propensity score matching analysis.

Other than treatment type, the 265 pairs of patients were matched based on all other potential prognostic factors, including age, sex, primary tumor size, minor extrathyroidal extension, multifocality, number of lymph node metastases, and lymph node ratio.

Participants were a mean age of 37 years and 66% were female.

With a median follow-up of 60 months in the lobectomy group and 58 months in the total thyroidectomy group, structural recurrences occurred in 7.9% (21) and 6.4% (17) of patients, respectively, which was not significantly different.

The primary endpoint, 5-year rate of recurrence-free survival, was also not significantly different between the lobectomy (92.3%) and total thyroidectomy groups (93.7%) (adjusted hazard ratio, 1.10; P = .77).

In a further stratified analysis of patients treated with total thyroidectomy along with RAI (n = 75), the lack of a significant difference in recurrence-free survival versus lobectomy remained (adjusted hazard ratio, 0.59; P = .46).

The results were similar in unadjusted as well as adjusted analyses, and a power analysis indicated that the study had a 90% power to detect a more than 4.9% difference in recurrence-free survival.

“Given the lower complication rate of lobectomy, a maximal 4.9% recurrence-free survival difference is acceptable, which enhances the reliability of the study results,” the authors say.

They conclude that “our findings call into question whether cN1b alone [ipsilateral clinical lateral neck metastasis papillary thyroid cancer] should be an absolute determinant for deciding the optimal extent of thyroid surgery for papillary thyroid cancer.”

With Total Thyroidectomy, RAI Can Be Given

An important argument in favor of total thyroidectomy is that with the complete resection of thyroid tissue RAI ablation can then be used for postoperative detection of residual or metastatic disease, as well as for treatment, the authors note.

Indeed, a study using the Surveillance, Epidemiology, and End Results (SEER) database showed RAI ablation is associated with a 29% reduction in the risk of death in patients with intermediate-risk papillary thyroid cancer, with a hazard risk of 0.71.

However, conflicting data from Memorial Sloan-Kettering Cancer Center suggests no significant benefit with total thyroidectomy and RAI ablation.

The current study’s analysis of patients treated with RAI, though limited in size, supports the latter study’s findings, the authors note.

“When we performed further stratified analyses in patients treated with total thyroidectomy plus RAI ablation and their counterparts, no significant difference was found, which conformed with [the] result from the whole cohort.”

“Certainly, the stratified comparison did not have enough power to examine the effect of RAI ablation on tumor recurrence subject to the limitation of sample size and case selection [and] further study is needed on this topic,” they write.

Some Limitations Warrant Cautious Interpretation

In their editorial, Mulder and Duh note that while some previous studies have shown similar outcomes relating to tumor size, thyroid hormone suppression therapy, and multifocality, “few have addressed lateral neck involvement.”

They suggest cautious interpretation, however, due to limitations, acknowledged by the authors, including the single-center nature of the study.

“Appropriate propensity matching may mitigate selection bias but cannot eliminate it entirely and their findings may not be replicated in other institutions by other surgeons,” they note.

Other limitations include that changes in clinical practice and patient selection were likely over the course of the study due to significant changes in American Thyroid Association (ATA) guidelines between 2009 and 2017, and characteristics including molecular genetic testing, which could have influenced final results, were not taken into consideration.

Furthermore, for patients with intermediate-risk cancer, modifications in post-operative follow-up are necessary following lobectomy versus total thyroidectomy; “the role of radioiodine is limited and the levels of thyroglobulin more complicated to interpret,” they note.

The study and editorial authors had no disclosures to report.

JAMA Surg. Published December 1, 2022. Study, Editorial

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