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Critical evaluation: hospital volume as a factor influencing the choice of thyroid cancer surgery?

A large number of studies have demonstrated the positive correlation between high-volume hospitals with better outcomes in high-risk procedures. These include pancreaticoduodenectomies, liver resections, pneumonectomies, colectomies, gastrectomies and oesophagectomies. In a nationwide study, high-volume hospitals were found to be associated with significantly lower perioperative mortality rates, with the reduction in risk being more pronounced in elderly patients. In terms of oncological outcome, rectal cancer operation performed by high-volume surgeons are found to be associated with a lower rate of local recurrence. A similar relationship between volume and clinical outcomes has also been observed in endocrine surgery. High-volume thyroid surgeons were associated with shorter hospital stays and lower risk of recurrent laryngeal nerve injury and hypoparathyroidism. Hence, accumulating evidence is in support of a specialty approach in managing these patients. In management of thyroid carcinomas, the extent of surgery depends on the histological cell type and the size of the lesion. In general, carcinomas less than 1 cm can be adequately treated by lobectomy alone. For papillary carcinomas that are greater than 1 cm in diameter, a total thyroidectomy has been shown to be associated with lower risk of recurrences and improved survival, and this should be the preferred procedure. In follicular carcinomas, patients in the low-risk category (age younger than 45 years, tumour smaller than 2 cm in diameter with minimal capsular invasion) can be managed by lobectomy alone, while those falling in the high-risk group (patients more than 45 years old and tumours more than 4 cm in diameter) should be managed by a near-total or total thyroidectomy. In a recent article by Lifante et al., the relationship between hospital volume and the choice of operation for thyroid cancers was examined in a population-based analysis. Data were extracted retrospectively from a French database of all hospitals in the RhoneAlpes area of France. Hospitals were categorized according to the annual volume of procedures: those that perform less than 10, 10 to 99 or at least 100 operations per year. Patients with thyroid cancers larger than 1 cm were identified and the factors associated with the extent of surgery were analysed by multivariate analysis. Among the factors considered for analyses, total thyroidectomies were found to be strongly associated with high-volume hospitals and the risk of a unilateral procedure for thyroid cancer increased by 2.46 in low-volume hospitals. Hence, the authors concluded that a significant relationship exists between the hospital volume and the decision to perform bilateral surgery for thyroid carcinoma, and that thyroid cancer surgery should be performed in high-volume centres. This study was a large-scale population-based analysis on the practice of surgery for thyroid carcinoma. It has shown that most patients (80.1%) in this region of France have received total thyroidectomies performed in mediumand high-volume hospitals. This practice is in concordance with recommendations from published guidelines. However, the paper also attributed a causal relationship between the performances of unilateral lobectomies (inadequate surgery) with low-volume hospitals. While this may be a possible explanation of the observed findings, one should be wary of the possible biases or pitfalls in the interpretation of the data. It is well known that computer databases are an excellent source of providing useful population data. However, the accuracy of such depends on a great deal on the accuracy of the coding practices in the hospitals. In one study, up to 40% of the information included in the population-based database was inaccurate and this may be due to missing information or misinterpretation of records by non-clinical staff. In the current paper, patients with thyroid malignancy were identified according to the diagnostic coding. The accuracy of this search could be improved by using different keywords for drawing data, followed by cross-checking with the final pathology and validating the identified cases. This was not performed in this study. The paper also assumes that only thyroid lesions larger than 1 cm were investigated in France. It did not take into consideration scenarios where lesions smaller than 1 cm would be needle aspirated due to clinical or radiological suspicion of malignancy. These patients could be adequately treated by a lobectomy alone regardless of being operated in highor low-volume hospitals. On the other hand, the variables listed for multivariate analysis only included sex, age, hospital category and year of hospital admission. Important tumour characteristics such as the histological cell type, size, the degree of differentiation and the presence of capsular invasion were not included in the analysis. These factors will influence the choice of surgery and it would be interesting to see whether lobectomies were performed more so in low-risk patients or no relationship exists between these factors in this population. Furthermore, it was also shown that low-volume hospitals only perform 18.2% of the annual number of thyroidectomies and about a third of these cases are lobectomies. Although this may reflect the choice of operation in low-volume hospitals, it can also be a reflection of the patient selection or referral patterns in these institutions. Surgeons practicing in these hospitals are more likely to refer morbid, re-operated patients or patients with nodal metastasis to specialized hospitals and only operate on patients who require a unilateral procedure. Additional information on the preoperative staging, the morbidities and mortalities, may help further characterize the case-mix among different hospitals. These are important JOURNAL CLUB