Lymph-Node Dissection for Papillary Thyroid Cancer Questioned

Miriam E. Tucker

April 16, 2013

CHICAGO — Routine prophylactic central lymph node dissection (PCLND) following total thyroidectomy for low-risk papillary thyroid cancer (PTC) is not cost-effective unless the recurrence risk of the cancer is above a certain threshold, of around 11.6%, a new modeling study has found.

The findings suggest that use of PCLND should be individualized based on risk for recurrence, as well as the likelihood of recurrent laryngeal nerve (RLN) injury and hypoparathyroidism, Kyle Zanocco, MD, from Northwestern University Feinberg School of Medicine, Chicago, said when presenting the study here at the annual meeting of the American Association of Endocrine Surgeons.

Central neck dissection is recommended for all patients with thyroid cancer if there is clinical evidence of lymph-node involvement. Without evidence of lymph-node involvement, neck dissection is also recommended for medullary thyroid cancers greater than 1 cm. However, for PTC, "the practice pattern of PCLND in the United States is not well described, and there is considerable debate in the scientific literature about the utility of the procedure," Dr. Zanocco told Medscape Medical News.

Routine PCLND following total thyroidectomy in patients with node-negative PTC reduces the risk for disease recurrence, but it also raises the risk for surgical complications, he explained.

But 2 audience members and the session chair, John A. Olson, Jr., MD, from the division of general and oncologic surgery at the University of Maryland Medical Center, Baltimore, said the study didn't take into account the potential cost saving from using the information derived from PCLND to prevent unnecessary radioiodine treatment.

Dr. Olson said he typically asks the referring endocrinologist if having the central nodal information available would affect the management strategy. If the endocrinologist needed the information to make a radioiodine decision, he would do the dissection. "This highlights the importance of communication between all the people involved in the care of the patient. It's part and parcel of team-based care," he told Medscape Medical News.

PCLND Should Be Limited to Experienced Surgeons

In the study, Dr. Zanocco and colleagues used a reference case scenario of an otherwise-healthy 40-year-old without previous neck surgery undergoing total thyroidectomy for a clinically node-negative PTC (tumor stage, T1b).

Assumptions based on the literature included a lifetime recurrence rate of 6% after thyroidectomy alone and a risk reduction of 75% with PCLND. The additional risks of recurrent laryngeal injury and permanent hypoparathyroidism with PCLND were assumed to be 0.25%, and the risk of each of these complications during reoperation for recurrence was 3%.

Cost assumptions included $5500 for the cost of thyroidectomy, with PCLND adding approximately $500 to this cost. Reoperation for recurrence was estimated to be $8887.

Routine PCLND added to total thyroidectomy had an expected strategy cost of $10,315, with an effectiveness of 23.786 quality-adjusted life-years (QALYs). For total thyroidectomy without PCLND, the cost was $10,149, with 23.793 QALYs. Thus, the PCLND added to the cost of total thyroidectomy but was not cost-effective, Dr. Zanocco explained.

In a sensitivity analysis using a threshold for cost-effectiveness of $100,000/QALY, the lifetime recurrence rate would need to be 11.6% or higher in order for PCLND to be cost-effective. With the reference case, the recurrence rate was just 6% and therefore PCLND would not be cost-effective, he said.

A second sensitivity analysis showed that the cost of reoperation would need to be $29,000 or higher, as opposed to the reference estimate of approximately $9000, for PCLND to be cost-effective.

And a third analysis examining the additional risk of RLN injury and permanent hypoparathyroidism during PCLND found that, to be cost-effective in a healthy low-risk patient, the rate of RLN injury would need to be less than 0.04% and that of hypoparathyroidism less than 0.05%, in contrast to the 0.25% of the reference case.

"Use of PCLND in papillary thyroid cancer should be limited to those patients in whom the risks of surgical complication are outweighed by the potential benefits of recurrence reduction. Experienced thyroid surgeons with low complication rates are in the best position to benefit patients by performing this procedure," Dr. Zanocco told Medscape Medical News.

Study Did Not Take All Things Into Consideration

"This was very much focused on surgical decision-making and didn't account for the total care of the problem," session moderator Dr. Olson told Medscape Medical News.

"As we pay closer attention...to things like episodic care, global payments, and full treatment, these cost-effectiveness analyses are not going to be able to be so compartmentalized as in this surgical example but [instead should take into account] the entire spectrum of care and how each component may affect the next. I think this was an interesting study but clearly was inadequate to answer the question."

Dr. Zanocco acknowledged that his model didn't include all possible variables. However, he said, "The model assumes all patients receive identical treatment afterward. It's an imperfect assumption, but I think that the key variables were captured."

Neither Dr. Zanocco nor Dr. Olson has reported relevant financial relationships.

American Association of Endocrine Surgeons. Abstract 1, presented April 14, 2012.

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