Surgical Risk after Unilateral Lobectomy Versus Total Thyroidectomy: A Review of 47,434 Patients

  

    
Effect of    thyroidectomy modality on outcomes*
    
P
    
OR
    
95% C.I.for    OR
  
  

    
 
    
 
    
Lower
    
Upper
  
  

    
Overall    Complications
    
0.725
    
1.209
    
0.42
    
3.476
  
  

    
Medical    Complications
    
0.784
    
0.843
    
0.249
    
2.852
  
  

    
Surgical    Complications
    
0.044
    
0.726
    
0.532
    
0.991
  
  

    
Return to    the OR
    
0
    
0.359
    
0.311
    
0.415
  
  

    
Readmission
    
0.385
    
1.329
    
0.7
    
2.522
  

Table 3:  Risk-adjusted analysis. Odds ratios reflect risk of total thyroidectomy (with respect to reference group of unilateral thyroidectomy) for the given adverse event.

Discussion

The NSQIP database is a unique and robust database with large volumes that can support critical analyses of risk factors with small confidence intervals. NSQIP collects data from both major academic tertiary-care medical centers as well as community hospitals, thereby capturing a broad snapshot of procedures and patients with their preoperative risks and postoperative outcomes. Because the data is prospectively collected and validated by a highly-trained and dedicated surgical clinical nurse reviewer (SCNR), the NSQIP has a large advantage over other registry and Medicare-based analyses that are primarily administrative discharge datasets without emphasis on accuracy.

We identified 47,434 thyroidectomy patients. Overall rates of total, surgical, and medical complications, rep-operation, readmission and mortality were: 1.5%; 0.4%; 1.1%; 2.2%; 2.5%; and 0.05%, respectively. Previous research has demonstrated a low rate of morbidity for all thyroid operations (3.8%) [13]. Commonly reported overall complication rates for thyroid operations are in the following ranges: bleeding 0.1–3%, pneumonia 1%, wound infection 0.25–2%, urinary tract infections 0.2%, and cardiac morbidity 0.2–0.9% [14- 16]. When the NSQIP reporting hospitals are used as a benchmark, it appears that thyroid surgery continues to have an excellent safety profile.

Aside from decreased morbidity and cost savings, the use of TT versus UL is relevant for a number of thyroid cancer subtypes, including papillary thyroid cancer (PTC), Hurthle cell microcarcinomas, and well-differentiated thyroid microcarcinomas (WDTC). Thyroid lobectomy has been shown in previous literature to have less associated vocal and throat function morbidity, and is associated with lower cost and hospital length of stay than total thyroidectomy [17,18]. Current guidelines recommend TT for PTC tumors greater and 1.0 cm, in spite of the increased associated morbidity. Adam, et al evaluated 61,775 patients with PTC from the National Cancer Database, and found no difference in survival in TT versus UL, regardless of tumor size [19]. Lee, et al made a similar conclusion in their study of 2,014 patients [20]. However, Ebina, et al found decreased survival after UL in patients > 50 years old, those with massive extrathyroidal extension, or large (>3 cm) lymph node metastasis) in a study of 1,187 patients from a single center [21]. Of note, these studies only evaluated survival and tumor recurrence, as the respective datasets were not capable of analyzing other outcomes. Ogilvie, et al, reviewed 346 patients with WDTC and found that UL was not sufficient for local tumor control in WDTC patients with tumor size between 6-10 mm, in spite of American Thyroid Association guidelines recommending UL alone [22]. Kuo, et al, found poor survival for patients with Hurthle cell microcarcinoma in a study of 22,738 patients, regardless of the extent of resection [23]. Thyroid tumors can recur as a result of positive margins, microsatellite disease, or unrecognized nerve invasion. A statistical evaluation of the presence of histologic tumor subtypes, positive surgical margins, extent of locoregional disease, need for postoperative radiation, and tumor recurrence is beyond the level of detail available in ACS-NSQIP. The dataset does have a variable for “disseminated cancer” (referring to stage IV disease), which was significantly elevated in the TT group (p < 0.001; Table 1).

In addition, preoperative diagnosis codes identified thyroid malignancy as the reason for surgery in 88% of cases, and goiter in 8% of cases, with non-specified reasons making up the remaining 4% of cases. Data analysis when stratifying versus preoperative diagnosis only demonstrated continued significant increased in return to the OR for UL in the setting of thyroid malignancy, but not goiter (data not shown). This finding likely indicates that unilateral goiter can be successfully managed with UL with proper selection, while there continues to be a significant rate of conversion from UL to TT for patients with thyroid carcinoma (in spite of patient selection) [24-26]. Further development of the NSQIP dataset may facilitate more granular detail with regards to indications for surgery, use of completion thyroidectomy after lobectomy, and use of adjuvant therapies (e.g., radioactive iodine, levothyroxine).

One analysis evaluated the NSQIP database for trends in thyroidectomy and parathyroid outcomes between different specialties [27]. They concluded that there was no difference in outcomes or case complexity between general surgery and otolaryngology, that operative time was less for general surgery (115 versus 123 minutes), and that duration of hospital stay beyond 1 postoperative day was more frequent for otolaryngology (8% vs 5%). One weakness of their study was that their data set included 51,470 cases from general surgery and only 3,932 cases from otolaryngology, a reflection of the fact that NSQIP captures far more general surgery cases than surgical subspecialty cases. Furthermore, the percentage of thyroidectomy cases vs parathyroidectomy cases was higher for otolaryngology (86%) than general surgery (68%), which may have influenced overall average operative times and hospital stays. Our analysis did not detect any differences in total, surgical, or medical complications, reoperation, readmission, or mortality between surgical specialties performing thyroidectomy (i.e., general surgery, otolaryngology, thoracic surgery, and plastic surgery). A more valuable distinction may be surgical oncology specialization with respect to the performing surgeon; however, NSQIP does not identify this variable.

A 2012 NSQIP report showed that patients undergoing either thyroidectomy or parathyroidectomy, or both had a 30-day mortality of 0.08%, 0.16%, and 0.2%, respectively. They identified mean length of stay (LOS) values at 1.1 days, 1.1 days, and 1.4 days, respectively. Congestive heart failure (CHF), dependent functional status, dialysis dependence, and chronic corticosteroid use were significantly associated with increased LOS and postoperative adverse events [28]. Preoperative pneumonia and new exacerbation of CHF are well documented comorbidities that affect postoperative pulmonary complications [29,30]. Incentive spirometry, head of bed elevation, ambulation, and oral hygiene have been shown to decrease these complications [31,32].

A 2014 NSQIP study assessed how various preoperative comorbidities and intraoperative variables were tied to thyroidectomy outcomes [33]. In an analysis of 38,577 patients they found that risk factors independently associated with morbidity after thyroidectomy included hypertension, diabetes, advanced age greater than 70 years, COPD, and dialysis. Interestingly they found that the surgical approach was related to the rate of return to the operating room. As compared with a partial thyroidectomy, patients undergoing a total thyroidectomy were 73% less likely to return to the operating room and those undergoing substernal thyroidectomy were 37% less likely to return to the operating room. We similarly found an increased utilization of TL in patients older than 70 years of age (10.6% versus 10%, p = 0.021).

In our study the 30-day mortality was 0.03% for UL and 0.06% for TT. This mortality rate compares well with mortality rates of other procedures such as pancreatectomy (8.3%), coronary artery bypass graft (3.5%), craniotomy (10.7%), and repair of aortic aneurysm (3.9%) [34]. The morbidity rates found in our study were also low: 1.14% for UL and 1.64% for TT. This underscores the relative safety profile of thyroidectomy procedures. Thyroidectomy surgeons and hospitals should use these data as a benchmark to compare their own rate of complications and for quality improvement initiatives.

Interestingly, UL was significantly more likely than TT to be associated with surgical complications and return to OR (Table 3). With regard to surgical complications, there was a greater incidence of wound dehiscence and deep SSI in the UL group, indicating that some unidentified factor contributes to increased surgical complications in this cohort. It is possible that the challenge of partial thyroidectomy through a limited skin incision results in greater soft tissue trauma and consequent AE, although the techniques for UL versus TT are nearly identical. While the surgical extent of TT is greater, it may be that the technical sophistication of UL is more, in that it entails organ-sparing of half of the thyroid gland. Of note, when we separated surgical complications by type (i.e., superficial/ deep/ organ space wound infection, wound dehiscence, etc) and performed additional multivariable analysis for TT versus UL, no one specific complication type was significantly elevated in the UL group. NSQIP is limited in that it does not track surgeon experience (which has been shown to decrease the risk of AE after UL or TT). However, it is possible to track the reason for reoperation and/or readmission. After analyzing causes for reoperation and readmission, we found that over 70% of reoperations and readmissions were for cancer, neoplasm, and/or goiter (Table 4). These cases are thus attributable to completion thyroidectomy, and not reoperation or readmission for postoperative complications. After excluding these cases from statistical analysis, there were no longer any significant differences in UL versus TT groups for reoperation and/or readmission (1.9% vs 1.9%, p=.91 for reoperation; 2.5% vs 3.1%, p=.52 for readmission). Based on this preliminary analysis, it appears as though the vast majority of reoperations and readmissions are thus attributable to the need for completion thyroidectomy after UL, and not any specific AE requiring surgical intervention. This finding would suggest that UL does not confer any specific risk for reoperation greater than TT, outside of the possible need for completion thyroidectomy. Thus, future research may be useful identifying which patients will go on to ultimately require completion thyroidectomy, versus any specific modification of the techniques for UL. Similarly, we found a higher rate of readmission on univariate analysis for TT, as opposed to UL. However, regression analysis demonstrated that modality choice does not confer increased risk of readmission, which would suggest that there is some other reason that readmission rates are higher for TT. Given that this outcome is partially, but not totally ameliorated when accounting for completion thyroidectomies, it suggests that there are other, unidentified factors contributing to these results.

  

    
Post-operative    Diagnosis for Patients who Returned to the OR
    
 
    
 
  
  

    
Diagnosis
    
Unilateral    (n=587)
    
Diagnosis
    
Total    (n=442)
  
  

    
Malignant    neoplasm of thyroid gland
    
51.30%
    
Malignant    neoplasm of thyroid gland
    
29.40%
  
  

    
Nontoxic    uninodular goiter
    
15.50%
    
Nontoxic    multinodular goiter
    
29%
  
  

    
Benign    neoplasm of thyroid glands
    
9.20%
    
Benign    neoplasm of thyroid glands
    
5.40%
  
  

    
Nontoxic    multinodular goiter
    
6.60%
    
Goiter    unspecified
    
5.40%
  
  

    
Neoplasm of    uncertain behavior of other and unspecified endocrine glands
    
2.90%
    
Toxic    diffuse goiter without thyrotoxic crisis or storm
    
4.80%
  
  

    
Goiter    unspecified
    
2.20%
    
Nontoxic    uninodular goiter
    
4.50%
  
  

    
Unspecified    disorder of thyroid
    
1.90%
    
Chronic    lymphocytic thyroiditis
    
3.40%
  
  

    
Unspecified    nontoxic nodular goiter
    
1.40%
    
Toxic    multinodular goiter without thyrotoxic crisis or storm
    
2.90%
  
  

    
Post-operative    Diagnosis for Patients Who Were Readmitted
    
 
    
 
  
  

    
Diagnosis
    
Unilateral    (n=138)
    
Diagnosis
    
Total    (n=311)
  
  

    
Malignant    neoplasm of thyroid gland
    
34.10%
    
Malignant    neoplasm of thyroid gland
    
33.40%
  
  

    
Nontoxic    uninodular goiter
    
15.90%
    
Nontoxic    multinodular goiter
    
26.70%
  
  

    
Benign    neoplasm of thyroid glands
    
15.20%
    
Goiter    unspecified
    
5.80%
  
  

    
Nonotoxic    multinodular goiter
    
11.60%
    
Nontoxic    uninodular goiter
    
5.80%
  
  

    
Goiter    unspecified
    
3.60%
    
Toxic    diffuse goiter without thyrotoxic crisis or storm
    
5.10%
  
  

    
Unspecified    disorder of thyroid
    
2.90%
    
Benign    neoplasm of thyroid glands
    
4.50%
  
  

    
Neoplasm of    uncertain behavior of other and unspecified endocrine glands
    
2.20%
    
Chronic    lymphocytic thyroiditis
    
3.50%
  
  

    
Nontoxic    uninodular goiter
    
2.20%
    
Unspecified    nontoxic nodular goiter
    
2.30%
  
  

    
 
    
Unilateral    (n=2275)
    
Total    (n=4066)
    
P
  
  

    
Return to    the OR
    
1.90%
    
1.90%
    
0.91
  
  

    
 
    
Unilateral    (n=448)
    
Total    (n=977)
    
 
  
  

    
Readmission
    
2.50%
    
3.10%
    
0.52
  

Table 4:  Diagnosis codes associated with return to operating room and readmission.