1 2 3 4 5 6 Considering the growing evidence for this volume–outcome relationship for esophageal cancer surgery, we decided to investigate the outcome of these procedures in our region from 1990 until 1999. During this study period none of the 11 hospitals affiliated with the Comprehensive Cancer Center Leiden (CCCL) in the Netherlands performed more than seven esophageal resections a year; all are considered low-volume hospitals (LVH). In contrast to most volume–outcome studies, we decided to use clinical data obtained from the original patients’ files. We retrieved information about comorbid diseases, tumor characteristics, treatment, and outcome. Next to hospital mortality, several determinants of outcome were examined, such as the number of tumor-free margins and complication rates. Assuming that survival is an essential indicator for quality in cancer surgery, we included a 5-year follow-up. To put our data in the right perspective, we compared these outcomes to the results of the topographically nearest high-volume referral center (HVH). PATIENTS AND METHODS All surgically treated esophageal carcinomas in the period 1990–1999 were retrospectively identified through the Leiden Cancer Registry (LCR) of the Comprehensive Cancer Center Leiden (CCCL), in which all cancer patients treated in the midwestern part of the Netherlands are registered (1.7 million inhabitants). All 11 hospitals gave consent to participate in this audit and were visited by two investigators to retrieve the original patient files. Patient demographics, pathological notes, data on the surgical and (neo)adjuvant treatments, comorbidity as well as postoperative morbidity, mortality, length of stay, radicality of the resection, and long-term survival could all be retrieved from the patient’s files. All tumors were staged according to the UICC TNM classification of 1997. This was done by two independent researchers. The obtained pTNM stages were checked with the pTNM stages registered in the LCR. Any discrepancies were discussed between the researchers and a trained data manager from the CCCL. If consensus could not be reached, the pTNM stage was registered as “unknown.” To make a comparison with the outcomes of the nearest high-volume center, data were categorized according to the database of this center. In this hospital, data of patients operated on for an esophageal carcinoma are prospectively collected by a trained data manager. P Survival was calculated as the difference between date of surgery and either the date of death or the date of last patient follow-up. For both groups, follow-up of the patients was completed until December 31,, 2005. Observed survival rates were estimated by using the Kaplan–Meier method. The log-rank test was used to assess differences in survival between patients who were operated in LVHs and the HVH. All analyses were conducted using SPSS software (version 12.0; SPSS Inc., Chicago. IL). RESULTS Hospital Volume 1 A  B 7 FIG. 1.  (A)  (B)  Patient, Tumor, and Treatment Characteristics 1 TABLE 1. a b Characteristics LVH HVH P No. of patients % No. of patients % Age (years) 65  64  .240   Range (years) 33–87  31–83   Gender     .072   Male 249 73 438 78    Female 93 27 123 22  Comorbidity     .078   No 142 42 273 49    1 organ system 111 32 179 32    2 organ systems 51 15 80 14    ≥3 organ systems 11 3 27 5    Unknown 27 8 2 0  Histology     .039   Adenocarcinoma 238 69 347 62    Squamous 96 28 193 34    Barrett’s dysplasia 4 1 6 1    Other 2 1 14 3    Unknown 2 1 1 0  Tumor localization     .740   Cervical esophagus 7 2 14 3    Mid esophagus 53 15 86 15    Distal esophagus 114 33 204 36    Gastroesophageal junction 166 49 251 45    Unknown 2 1 6 1  Stage (pTNM)     <.001   0 and I 43 12 61 11    II 162 47 214 38    III 107 31 186 33    IV 21 6 94 17   Unknown 9 3 6 1  (Neo)-adjuvant treatment     <.001   None 316 92 464 83    Chemotherapy 17 5 93 17    Radiotherapy 0 0 2 0    Chemoradiation 4 1 0 0   Unknown 5 2 1 0  Surgical approach     <.001   Abdomino-cervical 150 44 466 83    Thoraco-abdominal 97 28 60 11    Abdomino-thoraco-cervical 43 13 17 3    Abdominal 52 15 18 3  Anastomoses     <.001   Cervical 195 57 541 96    Thoracic 91 27 8 2    Abdominal 56 16 8 2    Unknown 0 0 4 0  Total No. of patients 342  561   a b Morbidity and Mortality 2 P 3 4 TABLE 2. a b Outcome LVH HVH P No. of patients % No. of patients % Margins     .93   R0 248 72 377 67    R1 55 16 161 28    R2 35 11 21 4    Unknown 4 1 2 1  Complications        Surgical complications 144 42 207 37 .01   General complications 191 56 207 37 <.001   No complications 89 26 247 44 <.001 Hospital stay      Median (days) 21  14  <.001 In-hospital         Mortality 45 13 28 5 <.001   Survival        Median (months) 21  22  .90   Range (months) (1–171)  (1–158)   Total No. of patients 342  561   a b TABLE 3. a b Hospitalsm In-hospital mortality No. of patients No. of deaths % HVH 561 28 5.0 LVH 1 16 2 12.5 LVH 2 19 2 10.5 LVH 3 28 2 7.1 LVH 4 25 3 12.0 LVH 5 14 1 7.1 LVH 6 28 2 7.1 LVH 7 34 2 5.9 LVH 8 64 12 18.7 LVH 9 44 10 22.7 LVH 10 6 2 33.3 LVH 11 64 7 10.9 Total No. of patients 903 73 8 a b TABLE 4. Univariate analysis of in-hospital mortality  Univariate analysis OR 95% CI P Region   <.001   HVH 1.00 a    LVH 2.88 1.76–4.72  Age (years)   .01   <50 0.19 0.04–0.79    50–59 0.51 0.25–1.04    60–69 1.00 a    >70 1.20 0.70–2.04  Gender   .20   Male 1.00 a    Female 0.67 0.36–1.24  Comorbidity   <.001   No 1.00 a    1 organ system 2.02 1.06–3.86    2 organ systems 4.51 2.30–8.85    ≥3 organ systems 4.97 1.92–12.83  Histology   .97   Adenocarcinoma 1.00 a    Squamous 0.99 0.60–1.65  Stage   .24   I 1.00 a    II 0.50 0.24–1.04    III 0.80 0.39–1.63    IV 0.65 0.26–1.61  Tumor localization   .33   Cervical/mid esophagus 1.00 a    Distal esophagus/gastroesophageal junction 1.41 0.71–2.80  Neoadjuvant treatment   .14   No 1.00 a    Yes 0.49 0.20–1.25  Surgical approach   .31   Transhiatal 1.00 a    Transthoracic 1.51 0.90–2.54 .12 Anastomosis   .46   Cervical 1.00 a    Thoracic 1.52 0.77–3.01    Abdominal 1.26 0.52–3.04  a 5 TABLE 5. Multivariate analysis of in-hospital mortality  Multivariate analysis OR 95% CI P Region   <.001   HVH 1.00 a    LVHs 3.05 1.82–5.11  Age (years)   .10   <50 0.22 0.05–0.96    50–59 0.60 0.29–1.25    60–69 1.00 a    >70 1.07 0.61–1.88  Comorbidity   .004   No 1.00 a    Yes 2.34 1.30–4.19  a Survival 2 P 3 4 FIG. 2. (in-hospital mortality included )  FIG. 3. (in-hospital mortality excluded )  FIG. 4. (in-hospital mortality excluded )  DISCUSSION Currently, there is extensive interest in comparing outcome of complex surgical procedures between high- and low-volume providers. Most of the studies are registry-based or relatively small. Our series offers additional proof to the volume–outcome relationship, because it is based on clinical data, retrieved from the original patient files. This allows us to make reliable comparisons for comorbidities and tumor stage, which proved to be important prognostic factors for in-hospital mortality and survival. 8 2 9 4 5 10 11 2 6 TABLE 6. Volume–outcome articles for in-hospital mortality after esophagectomy 1998–2006 Author Journal/Year Data Volume “cut-off” Conclusion 32 Ann Thorac Surg Adm <6> S 33 BMJ Adm <9> NS 12 BMJ Clin <10–20> S 34 Ann Surg Adm <22> S 35 Arch Surg Adm <4–9> S 36 CMAJ Adm a S 37 Surgery Adm <7> S 9 N Engl J Med Adm <2–4–7–19> S 11 Br J Surg Clin <19> NS 10 Br J Surg Clin a NS 38 Ann Thorac Surg Adm <4–15> S 7 Cancer Adm <10–20> S 39 Ann Thorac Surg Adm <6> S 40 J Thorac Cardiovasc Surg Adm <5> S 41 J Am Coll Surg Adm <10–20–50> S 42 JAMA Mixed <5–10> S 43 J Gastrointest Surg Adm <1–2–4–6> S a Adm denotes administrative data; Clin denotes clinical data; S denotes significant; NS denotes not significant. In the present study, independent data managers collected data retrospectively from the patient files. Not only the (in-hospital) mortality rate was obtained, but also a range of other outcome data, such as complication rates, resection margins, length of stay, and long-term survival. In our opinion the latter is an important performance indicator in surgical oncology, surprisingly sporadically mentioned in the volume–outcome literature. 7 13 14 15 18 19 22 23 27 28 25 In conclusion, our study shows that hospital volume is an important determinant of perioperative morbidity and mortality in esophageal cancer surgery. Nevertheless, volume in itself is no guarantee for high quality of surgical care in a specific institution. Selecting (only) favorable patients can be the basis of superior results. Therefore, case-mix adjustments are essential in the assessment of surgical performance of different institutions.