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Reply to the Letter to the Editor "Laparoscopic Distal Pancreatectomy for Pancreatic Ductal Adenocarcinoma: time for a Randomized Controlled Trial? Results of an All-inclusive National Observational Study".

Reply: We are very grateful to de Rooij et al 1 for their careful reading of our article on laparoscopic and open distal pancreatectomies (DP) for pancreatic ductual adenocarcinoma (PDAC) and their constructive comments. The first refers to the higher number of DP for PDAC performed annually in France (n 1⁄4 450) compared with the US (n 1⁄4 385) despite having one fifth of the population. Such a comparison should be interpreted with caution. Data from the US are derived from the National Cancer Database (NCDB) that does not comprehensively records all malignancies nationally. For example, the annual number of pancreatic cancers reported to the NCDB was 23,274, whereas it was 48,960 based on the data of the American Cancer Society. In comparison, the number of incident pancreatic cancer in our database (n 1⁄4 12,110 in 2012, unpublished data) almost perfectly match that of the Institut National du Cancer (INCa), the French national agency on cancer (n 1⁄4 11,662 in 2012). Based on these incidence data, the annual number of DP for PDAC reported in our study makes sense. It is estimated that 10 to 20% of patients with PDAC are eligible for initial resection and that approximately one-third of initially staged nonresectable tumor patients would be expected to have resectable tumors after neoadjuvant therapy. Considering a 20% resection rate in France (around 2500 patients), the annual number of DP for PDAC that we report represent approximately one fifth of pancreatic resections for this indication, which is in agreement with other series. This would also mean that 3.7% of PDAC patients undergo DP (ie, 450 out of 12,000 patients). Using the data from the NCDB, this proportion would be 1.6% (ie, 385 out of 23,274 patients) in the US. Possible explanations for this difference are a more liberal use of pancreatic resections or more efficient regionalization in France than in the US, as previously shown for hepatic resections. The second comment is on the accuracy of the diagnosis of PDAC as the databases used in our study rely on the International Classification of Diseases ICD-10, but do not contain detailed pathology data. The contamination with endocrine tumors is unlikely as patients who underwent a DP during the study period with an ICD-10 code C254 (that describes pancreatic endocrine tumors) were not included in the study population. In contrast, the ICD-10 neither contains a specific code for cystadenocarcinoma of the pancreas (but these tumors are rare), nor for intraductal papillary mucinous neoplasms (IPMN). Patients with a PDAC arising from an IPMN are therefore most probably included in the study population. Based on a recent systematic review and metaanalysis, invasive IPMN account for approximately 10% of PDAC. The median survival of 38 months after DP for PDAC in our series should not be compared with the 20-months median survival after pancreatoduodenectomy for PDAC recently reported on behalf of the French Association of Surgery (AFC) but with the 35-months median survival after DP for PDAC recently reported by the same AFC study group. The 3-year survival of 52% in our series is also only slightly higher than the 45% 3-year survival recently reported by others, who similarly reported better survival after DP than pancreatoduodenectomy for PDAC. These survivals are indeed greater than that reported by the Dutch multicenter study that de Rooij et al refer to. Of note, this Dutch study also highlighted that the median survival after DP for PDAC doubled when adjuvant chemotherapy was used and a more liberal use of adjuvant chemotherapy in France could explain part of the difference as adjuvant chemotherapy became the standard of treatment earlier in France that in the Netherland. We nevertheless acknowledge that survival curves in our study were constructed with the assumption that all patients died in a healthcare centre, whether acute, chronic, or home-care. This is however unlikely to have overestimated survival markedly. The percentage of patients dying at home in France from digestive diseases is 15%, one of the lowest rate in Europe, and probably most of them are included in the home-care facility database that was screened for the purpose of this study. In any case, this limitation is anticipated to be the same for patients undergoing open and laparoscopic DP. The DIPLOMA trial that de Rooij et al are launching is a remarkable initiative to overcome the selection bias inherent to our study and we hope that many centers will contribute to their effort.