The Effect of Day of the Week on Morbidity and Mortality From Colorectal and Pancreatic Surgery: An Analysis from the German StuDoQ Register

An analysis from the German StuDoQ register.

Background: A number of studies have revealed higher postoperative mortality after operations that were performed toward the end of the week. It is not yet known whether a day-of-the-week effect exists after visceral surgical procedures for cancer in Germany.

Methods: Data on resections of carcinomas of the colon, rectum (2010–2017), and head of the pancreas (2014–2017) (n = 19 703) that had been prospectively acquired by the Study, Documentation, and Quality Center of the German Society for General and Visceral Surgery were analyzed in relation to the day of the week on which the operation was performed. The primary endpoint was postoperative 30-day mortality; the secondary endpoints were complications, length of hospital stay, and MTL30 (a combined outcome criterion that is positive if the patient has died, is still in the hospital, or has been transferred to another acute care hospital 30 days after the index procedure).

Results: Resections of colon carcinomas that were performed on Mondays were associated with more advanced tumor stages (T4: 18.4% vs. 15.7%, p <0.001), higher 30-day mortality (3.5% vs. 2.3%, p = 0.004), and a more frequently positive MTL30 (10.5% vs. 8.5%, p = 0.004). Among patients who underwent pancreatic head resections, those whose procedures were on Tuesday had higher mortality (6.2% vs. 3.8%; p = 0.021). Among those who underwent surgery for rectal carcinoma, the day of the week on which the procedure was performed had no effect on postoperative morality. Multivariate analysis revealed that the independent risk factors for postoperative mortality were colonic resection on a Monday (odds ratio [OR]: 1.45; 95% confidence interval [1.11; 1.92], p = 0.008) and pancreatic head resection on a Tuesday (OR: 1.88 [1.18; 2.91], p = 0.006).

Conclusion: Elective surgery for carcinoma of the colon or pancreatic head is associated with slightly higher mortality if performed toward the beginning of the week. On the other hand, the day of the week has no effect on the outcome of surgery for rectal carcinoma.

There is much controversy about whether and to what extent the outcome of elective abdominal surgery is influenced by the day of the week the surgery is performed. A number of retrospective studies showed poorer outcomes in patients who underwent surgery later in the week (1, 2, 3, 4). These studies were not undertaken in the German healthcare system and show considerable heterogeneity with regard to acute and hospital care, making comparisons difficult and limiting the extent to which they can be applied to the German setting (5, 6).

The German Study, Documentation and Quality Center (StuDoQ, Studien-, Dokumentations- und Qualitätszentrum) was initiated by the German Society of General and Visceral Surgery (DGAV, Deutschen Gesellschaft für Allgemein- und Viszeralchirurgie) in 2010 for the purpose of quality assurance and identification of risk factors of surgical procedures, taking into account the underlying condition. The aim of our study was to evaluate, by analyzing the data of the StuDoQ Register, whether the day of the week on which oncological resections for cancer of the colon, rectum or pancreatic head were performed had an effect on postoperative mortality and morbidity. These operations are representative and standardized oncological abdominal procedures with high numbers of cases per entity in Germany (7).

Methods

Data source

The patient data were obtained from the StuDoQ Register (www.dgav.de/studoq; www.en.studoq.de); this prospective registry contains anonymized data of patients with diseases of the colon, rectum or pancreas who were treated in German hospitals. These data are provided in pseudonymized form by the participating hospitals (150 for colon and rectum, 70 for pancreas) and automatically checked for plausibility. Participation of the hospitals in the registries is voluntary. Based on these data, the hospitals receive a specific quality report about their standard of care in comparison to the other hospitals participating in the registry. Providing data to the registry is a requirement each hospital must fulfill for the DGAV certification process. Validation by cross-checking with institutional medical controlling data is part of the annual certification process. The publication guidelines are prepared by the DGAV (www.dgav.de/studoq/datenschutzkonzept-und-publikationsrichtlinien.html); the data security concept was established by TMF – Technology, Methods, and Infrastructure for Networked Medical Research (Gesellschaft der Technologie- und Methodenplattform für die vernetzte medizinische Forschung e. V., www.tmf-ev.de).

Study population

All patients on the StuDoQ Register entered in the period from 2010 to 2017 under colorectal surgery (n = 19 708) and from 2014 to 2017 under pancreatic surgery (n = 11 932) were screened for eligibility for inclusion in the study. The difference in the inclusion periods is explained by the later start of patient recruitment for the pancreas registry. Patients with confirmed diagnosis of colorectal cancer (CRC) and patients with partial pancreaticoduodenectomy (pylorus-resecting or pylorus-preserving) for adenocarcinoma of the pancreatic head were included in the study. The aim was to define a homogeneous sample of patients undergoing oncological and standardized surgical procedures in Germany. Patients with simultaneous resection of hepatic metastases, endoscopic tumor resection, missing information about the surgical procedure performed or about the location of the primary tumor were excluded from the study. Patients who underwent surgery on weekends or public holidays were also excluded. Patients who underwent emergency surgery during the week were analyzed separately. These patients were reported by the data-providing hospital assurgical emergencies (Figure). Detailed information about the assessed parameters are provided in the eBox.

Figure

The flowchart shows how the datasets analyzed were generated

eBox

Further details on Methods

Statistical analysis and study endpoints

The effect of the day of the week the surgery was performed was analyzed using a three-step approach and separately for resections of the colon, rectum and pancreatic head because of the known differences in patient characteristics and procedure-associated risk factors. First, the patient characteristics and endpoints were compared with respect to the day of the week the surgery was performed, using the chi-squared test, Student’s t-test or one-way ANOVA. In the second step, the days of the week were classified into two categories: Monday versus Tuesday to Friday or Tuesday versus Monday and Wednesday to Friday. These categories were subsequently compared among each other. Associations between day of the week and the endpoints of the studies were adjusted with regard to known prognosis-relevant co-variables in a multivariate logistic regression.

The primary endpoint of this study was the postoperative 30-day mortality for oncological colorectal resections as well as the postoperative in-house mortality for resections of the pancreatic head, because the latter better captures the complicated postoperative course after resection of the pancreatic head. Secondary endpoints included operative time, number of resected lymph nodes, overall morbidity and specific postoperative complications, length of hospital stay, and MTL30 status. The MTL30 is a validated endpoint, combining postoperative mortality, transfer to a hospital with a higher level of care, and length of hospital stay >30 days (8). Further details of the statistical analysis and the endpoints of this study are provided in the eBox.

Results

Patient characteristics

Altogether 17 204 patients diagnosed with colorectal cancer (11 462 [66.6%] colon resections, 5742 [33.4%] rectal resections) and 2499 resections of the pancreatic head in patients diagnosed with pancreatic cancer (PC) were included. Of the patients with CRC, 56.1% were male; the mean age was 69.5 ± 11.8 years, the mean body mass index (BMI) was 26 ± 5 kg/m². Of the patients with PC, 54.0% were male; the mean age was 68.8 ± 10.4 years, the mean BMI was 25.6 ± 4 kg/m² (eTable 1).

Table 1

Morbidity and lethality after elective resections of the colon, rectum and pancreatic head

eTable 1

Characteristics of patients who underwent elective surgery

Elective colon resections

For patients who underwent colon resection, a statistically significant difference with respect to the day of the week the surgery was performed was found for older patient age (p = 0.047) and shorter operative time (p = 0.006) on a Monday compared to the rest of the week. In addition, on Mondays a higher T stage (T4 18.4% vs. 15.7%, p<0.001), a higher UICC stage (p<0.001) and a higher rate of patients with distant metastasis (p = 0.008) was noted. There was no difference in N status or local R status. (eTable 2).

Table 2

Multivariate analysis of mortality and MTL30 after resections of the colon, rectum or pancreatic head

eTable 2

Characteristics of patients with elective colon cancer resection

Colon resections performed on a Monday resulted in a significantly higher mortality rate compared to other days of the week (3.5% versus 2.3%, p = 0.004). MTL30 status was significantly more common among patients who underwent colon resection on a Monday (10.5% versus 8.5%, p = 0.004). Overall morbidity after colon resection showed no significant difference. A significant difference was found for the number of patients with less than 12 resected lymph with respect to the day of the week (p = 0.007); however, no trend over the course of the week was noted (Table 1).

Elective rectal resections

For patients with rectal resection, statistically significant differences with respect to the day of the week the surgery was performed were found for preoperative need of nursing care (p = 0.010), coronary heart disease (CHD) (p = 0.002), metastatic cancer (p = 0.025), neoadjuvant treatment (p<0.001), rectal cancer height (p<0.001), and anastomotic technique (p = 0.005). There was no trend over the week. Likewise, no difference with respect to the day of the week the surgery was performed was found for the surgical pathology findings (eTable 3). Postoperative 30-day mortality, MTL30 status and overall morbidity showed no significant differences with respect to the day of the week the surgery was performed (Table 1).

eTable 3

Characteristics of patients with rectal cancer

Elective resections of the pancreatic head

In patients who underwent elective resection of the pancreatic head for pancreatic cancer, significant differences with respect to the day of the week the surgery was performed were found for BMI (p = 0.011) and preoperative loss of more than 10% of body weight (p = 0.004) on a Tuesday compared to the rest of the week. No differences were identified for pathology findings and UICC stages (eTable 4).

eTable 4

Characteristics of patients with pancreatic head cancer

Patients who underwent elective resection of the pancreatic head for PC showed significant differences in in-hospital mortality with regard to the day of the week (p = 0.031). Postoperative mortality was higher from Monday to Wednesday compared to Thursday and Friday (5.3% versus 2.8%). When comparing a single week day with the rest of the week, a significant difference was found for postoperative mortality to the disadvantage of Tuesday (6.2% versus 3.8%; p = 0.021). There were no differences with regard to postoperative complication rate, specific postoperative complications or length of hospital stay of the patient. The MTL30 status showed no difference in the comparisons of the days of the week among each other (Table 1).

Emergency resection for colorectal cancer

Patients who underwent emergency resection for colorectal cancer on a Monday had a significantly lower rate of coronary heart disease (15.1% versus 21.3%, p = 0.041), while the conversion rate from laparoscopic to open surgery was significantly higher (8.5% versus 6.8%, p = 0.030) (eTable 5). No differences with respect to the day of the week the surgery was performed were found for tumor location, procedure performed, pathology findings, and postoperative course (eTable 6).

eTable 5

Characteristics of patients with emergency resection for colorectal cancer

eTable 6

Morbidity and lethality after emergency resection for colorectal cancer

Multivariate analysis

In a multivariate regression analysis, elective colon cancer resection on a Monday was identified as an independent risk factor for postoperative 30-day mortality (odds ratio [OR]: 1.45; 95% confidence intervals: [1.10; 1.90], p = 0.008) and positive MTL30 (OR: 1.23 [1.04; 1.44], p = 0.012). Other independent risk factors for postoperative death within 30 days were ASA status (OR: 4.01 [3.23; 4.97], p<0.001) and UICC stage (OR: 1.27 [1.12; 1.44], p<0.001).

A patient’s ASA status was found to be an independent risk factor for postoperative mortality/positive MTL30 after elective rectal cancer resection (OR: 2.30 [1.5; 3.49], p<0.001 and OR: 2.13 [1.82; 2.52], p<0.001, respectively).

For postoperative mortality/positive MTL30 after resection of the pancreatic head, the following independent risk factors were identified:

• Patient age (OR: 1.05 [1.03; 1.07], p<0.001, and OR: 1.03 [1.02; 1.05], p<0.001, respectively)
• Full preoperative need of nursing care (OR: 16.6 [5.39; 48.5], p<0.001, and OR: 23.4 [7.31; 103.9], p<0.001, respectively), or
• Partial preoperative need of nursing care for the patient (OR: 2.93 [1.45; 5.59], p = 0.002, and OR: 2.07 [1.28; 3.28], p = 0.002, respectively), and
• Operative time (OR: 1.01 [1.00; 1.01], p<0.001, and OR: 1.00 [1.00; 1.01], p<0.001, respectively).

Furthermore, preoperative BMI was an independent risk factor for the occurrence of MTL30 after resection of the pancreatic head (OR: 1.03 [1.01; 1.06], p = 0.018). Tuesday as the day of the week the surgery was performed was an independent risk factor for postoperative mortality (OR: 1.88 [1.18; 2.91], p = 0.006) (Table 2).

Patient age (OR: 1.04 [1.005; 1.07], p = 0.02) and ASA status (OR: 4.1 [2.68; 6.14], p<0.001) were identified as independent risk factors for 30-day mortality after emergency resection for colorectal cancer. Risk factors for positive MTL30 included ASA status of the patient (OR: 2.29 [1.81; 2.89], p<0.001) and presence of CHD (OR: 1.58 [1.09; 2.27], p = 0.014) (eTable 7).

eTable 7

Multivariable analysis of emergency resections for colorectal cancer

Discussion

Based on the prospective registry data, this study found increased postoperative mortality after elective oncological resections of the colon or the pancreatic head among patients who underwent s,lurgery at the beginning of the week. Colon resection on a Monday and resection of the pancreatic head on a Tuesday were identified as independent risk factors for postoperative death. The day of the week had no effect on the postoperative course after elective resection for rectal cancer or emergency colorectal resection. Thus, in Germany a “day-of-the-week effect” exists in certain areas of elective oncological abdominal surgery.

In contrast to other published studies addressing this topic (1, 2, 3, 4), our study found an increased risk of postoperative death during the hospital stay in patients who underwent surgery at the beginning of the week instead of the end of the week. Previous studies reported for oncological resections performed in the second half of the week not only an increase in immediate postoperative mortality, but also a reduction in long-term survival of the patients (2, 9, 10). However, this effect has not been consistently described in the literature (11, 12, 13), making it more difficult to identify potential causes. With regard to colorectal resections, the increased postoperative mortality among patients who underwent surgery on a Friday is likely to be explained by patient selection and not by different hospital factors (14). A recent study from the Netherlands found no effect of the day of the week on the outcomes of elective colorectal surgery (15). Likewise, no differences in postoperative mortality and length of hospital stay related to the day of the week the surgery was performed were found in patients who underwent colorectal surgery and were treated according to the ERAS (Early Recovery After Surgery) protocol (16). Furthermore, no difference in surgical quality with respect to the day of the week was found, at least not in patients who underwent oncological resections of the esophagus or stomach 11–13). One of the previous hypotheses to explain the poorer outcomes towards the end of the week was that the first 48 hours of postoperative monitoring and care represent a critical period of time which determines the prognosis of the hospitalized patient (4, 5, 17). In 2011, evidence in support of this hypothesis emerged from a hospital survey in the UK, demonstrating that less than half of the patients who underwent abdominal surgery and died postoperatively had received acceptable medical care on the weekend (18). In our study, patients after resection of the pancreatic head, a procedure associated with frequent complications and an average postoperative mortality rate of 7.7% in Germany (19), appear to have received high-quality care on the weekend after surgery when the procedure was performed immediately before the weekend.

Complications with a relevant impact on prognosis, such as anastomotic leak after colorectal surgery, typically occur with a time delay (20, 21, 22, 23, 24). In a large registry study, Sparreboom et al. showed that the median interval between colorectal surgery and manifestation of an anastomotic leak was six days (25). Thus, it is possible that in patients undergoing surgery at the beginning of the week complications affecting mortality are treated on the weekend after the procedure. This would explain the finding that, despite identical complication rates, mortality is increased after surgery performed at the beginning of the week. This failure to rescue has already been published both for colorectal cancer and resections of the pancreatic head in dependence of the annual number of cases per hospital in Germany (26, 27, 28). Our study now provides evidence indicating a concentration of failure to rescue on the weekend in patients after oncological resections of the colon and pancreatic head. Consequently, the structural (equipment and staffing) capabilities of hospitals available outside of the core working hours are critical to the care provided to these patients. These factors, however, have no effect on the outcome of emergency resections for colorectal cancer performed during the week, possibly due to the overall low number of cases. However, since the data of the StuDoQ Register do not allow to identify the data-providing hospital, this hypothesis cannot be proven with the available data. The fact that a day-of-the-week effect was not observed among patients who underwent rectal resection may be related to the protective stoma that was created in 63.4% of patients with rectal resection. Because of the stoma, the development of an anastomotic leak over the weekend may have had no impact on mortality (29).

Interestingly, in the Global Comparators project, Ruiz et al. described a relative risk reduction for the postoperative 30-day in-hospital mortality in patients who underwent surgery in a hospital in the United Kingdom or the Netherlands on a Tuesday compared to patients who underwent elective surgery in a US hospital on a Monday (5). This effect, however, is not comprehensible in the individual countries and the risk of postoperative death increases with the day of surgery over the course of the week (5). In their study, the postoperative mortality rate after resection for rectal cancer also increased over the course of the week depending on the day of surgery, but this increase was not statistically significant and very low in international comparison (30, 31, 32). Strikingly, the number of surgical procedures performed on a Friday is considerably reduced in studies reporting an increased postoperative mortality in patients who underwent surgery on a Friday. This suggests a different work schedule on this day of the week (2, 5, 14). In our analysis, the number of surgical procedures performed for colonic cancer or pancreatic cancer was evenly distributed over the days of the week. In contrast, the majority of patients with rectal cancer underwent surgery on a Tuesday, Wednesday or Thursday which suggests a different scheduling compared to that for colon resections.

One limitation of the study lies in the fact that the hospitals providing data to the registry typically seek certification by the DGAV. Consequently, these data do not represent the nationwide average, but the outcomes achieved in hospitals with a proven high standard of care. Therefore, the mortality after resections of the colon and pancreatic head found in our study is considerably lowered compared to that in analyses which are based on nationwide data from German hospitals (19, 26, 27). On the other hand, the use of annually validated and prospectively acquired clinical data is a significant strength of our study compared to studies with higher patient numbers, but which are based on administrative data—especially when it comes to identifying independent factors during the risk adjustment step. In addition, we used strict definitions of the separately analyzed patient populations to account for differences in patient characteristics, postoperative complication risks and clinical outcomes. Because of the separate analyses, this study provides a highly accurate representation of the effect of the day of the week which was not present in patients who underwent elective rectal cancer surgery.

Conflict of interest
The authors declare that no conflict of interest exists.

Manuscript received on 31 October 2019, revised version accepted on 7 May 2020

Translated from the original German by Ralf Thoene, MD.

Corresponding author
PD Dr. med. Armin Wiegering
Klinik und Poliklinik für Allgemein-, Viszeral-, Transplantations-,
Gefäß- und Kinderchirurgie
Universitätsklinikum Würzburg
Oberdürrbacher Str. 6,
97080 Würzburg, Germany

Cite this as:
Anger F, Wellner U, Klinger C, Lichthardt S, Haubitz I, Löb S, Keck T,
Germer CT, Buhr HJ, Wiegering A: The effect of day of the week on morbidity and mortality from colorectal and pancreatic surgery—an analysis from the German StuDoQ register. Dtsch Arztebl Int 2020; 117: 521–7. DOI: 10.3238/arztebl.2020.0521

►Supplementary material

eBox, eTables:
www.aerzteblatt-international.de/20m0521

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