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Conversion surgery after active surveillance for low-risk papillary thyroid carcinoma (PTC) led to no clinically meaningful differences in outcomes as compared with immediate surgery, according to a matched cohort study.

Complication rates did not differ significantly between conversion procedures for suspected disease progression and conversion for reasons unrelated to disease progression. The 5-year overall survival rate was 100% after conversion for progressive disease and immediate surgery.

Rates of local, regional, and distant recurrence did not differ significantly between immediate surgery and delayed conversion, nor did 5-year recurrence-free survival (RFS), reported R. Michael Tuttle, MD, of Memorial Sloan Kettering Cancer Center in New York City, and co-authors in .

"This study provides additional support to previous observations indicating that, among patients with PTC choosing AS [active surveillance], CS [conversion surgery] for suspected disease progression is associated with surgical and subsequent oncologic outcomes that are similar to the outcomes seen among patients undergoing upfront IS [immediate surgery]," the authors wrote. "In addition, the surgical complexity and sequelae of CS due to disease progression were comparable to those of patients without disease progression."

"Despite the fact that the disease-progression CS group was enriched for those at the highest risk for adverse oncologic outcomes, CS at the time of disease progression was associated with excellent short-term outcomes," they added. "These findings are consistent with data from Japanese, Korean, and U.S. centers demonstrating that while disease progression is expected to develop in a small percentage of patients during AS, salvage therapy at the time of disease progression provided oncologic outcomes that are equivalent to outcomes expected in patients selected for IS."

The study's low rate of conversion for disease progression (39 of 550) may help "correct perceptions and make the case for greater AS adoption," which remains "disappointingly limited" in clinical practice, according to the authors of an .

"The broadening definitions of progression ... are excellent guardrails for safe conversion," wrote Allen S. Ho, MD, of Cedars-Sinai Medical Center in Los Angeles, and co-authors. "The findings ... are a reminder that progression is not correlated with death, but to surgical intervention shown to be safe. Finally, conversion was not associated with a greater extent of surgery or greater burden of care, as might be predicted from delayed surgery."

Active surveillance for low-risk thyroid cancer was and subsequently included in clinical guidelines in Japan in 2010 and the .

Limited data have accumulated related to outcomes with delayed surgery after active surveillance, most recently the results of a study among . Subsequently, 12.2% of the patients had conversion surgery, which was associated with low rates of nodal metastasis and favorable survival.

Tuttle and colleagues sought to contribute additional contemporary data related to conversion surgery following a period of active surveillance. The analysis included 550 patients with low-risk PTC who underwent surgery from January 2004 to December 2022, with a median surveillance duration of 3.6 years. They defined low risk according to .

The authors performed propensity matching to generate a cohort of 39 patients who had immediate surgery from January 1985 to December 2020. They were matched (for age, sex, tumor size, surgical procedure type, and follow-up duration) with the 39 patients who had progression-related conversion surgery after an initial period of active surveillance.

The data showed no meaningful differences (demographic, clinical, surgical) between the 39 patients who had progression-related conversion surgery and the 16 patients who had conversion for other reasons. Complication rates were 43.8% (seven of 16) versus 30.8% (12 of 39). Rates of vocal cord paresis, seroma, hypocalcemia, and wound infection did not differ between the two groups.

Comparison of the progression-related conversion group and the immediate-surgery group showed that tall-cell subtype was more prevalent in the conversion group (33.3% vs 5.1%). Otherwise, no meaningful differences were observed in clinical or surgical characteristics between the two groups.

The 5-year overall survival rate was 100% in both groups over a median postsurgical follow-up time of 40.3 months. Two patients in the disease-progression group had lymph node recurrences following surgery. Both patients were re-treated surgically and remain without evidence of recurrent disease, the authors noted. No patients in either group had local or metastatic recurrence. The 5-year RFS rate was 100% for patients who had immediate surgery and 86% for those who had surgery for disease progression.

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