Characteristics of the open and LAP groups
We identified 5,420 patients who underwent proctectomy for rectal cancer from 2005 to 2009 and otherwise met inclusion criteria for the study. LAP was used in 1,040 (19.2%), and 4,380 patients had open resection. lists the characteristics of the 2 patient groups. The 2 groups were similar in terms of age and race/ethnicity distribution. The proportion of female patients was higher in the LAP group. The mean body mass index was higher in the open group. There were no significant differences between the 2 groups for recent weight loss or functional status.
Characteristics of Patients (n = 5,420) Who Underwent Open or Laparoscopic-Assisted Proctectomy for Cancer
Several preoperative comorbid conditions were more prevalent in the open group, including diabetes mellitus, COPD, dyspnea, and hypertension. The prevalence of alcohol use was higher in patients who underwent LAP and there was no difference in smoking. There were no significant differences in the frequencies of other comorbid conditions such as coronary artery disease, CHF, peripheral vascular disease, neurologic disease, chronic steroid use, and bleeding disorders. Use of both neoadjuvant chemotherapy and radiation therapy was higher in the open resection group. An analysis of preoperative laboratory values demonstrated significant differences in mean values for WBC count, hematocrit, creatinine, SGOT, alkaline phosphatase, and serum albumin in the patients who underwent LAP. After adjusting for nonrandom assignment of treatment with propensity score quintiles, there were no significant differences between the LAP and open resection groups for any of the preoperative factors (, last column).
There were significant differences between the open and LAP groups for all of the operative variables that we analyzed, including wound class, ASA class, blood transfusions, length of operation, ostomy creation, abdominoperineal resection (APR), and work relative value units (). The percentage of contaminated, dirty, or infected wounds was higher in the open group. Similarly, the open group had a greater proportion of patients with an ASA class corresponding to severe or life-threatening systemic disturbance. Use of intraoperative blood transfusions was also higher in the open resection group. The mean operative time was considerably longer in the LAP group compared with the open. Mean work relative value units, a proxy for procedure complexity, was higher in the LAP group. About 58% of the patients who underwent open resection were given a colostomy or ileostomy, compared with 46% in the LAP group (p < 0.0001). The frequency of APR was also higher in the open resection group. There were small but statistically significant differences between the 2 groups for the NSQIP Probability of Morbidity and Mortality scores. The NSQIP Probability of Morbidity score for open patients was 0.207, compared with 0.182 in LAP patients (p < 0.0001). NSQIP Probability of Mortality scores were 0.010 and 0.008, respectively (p < 0.0001).
Adverse outcomes after proctectomy
The rate of any 30-day complication in the open resection group was 28.8%, compared with 20.5% in patients who underwent LAP (p < 0.0001). displays the rates of each type of complication, as well as other adverse outcomes. The open proctectomy group had significantly higher rates of superficial surgical site infection (11.8% versus 6.0%; p < 0.0001), sepsis (7.2% versus 4.7%; p = 0.0041), respiratory complications such as pneumonia (4.5% versus 2.8%; p = 0.0113), renal failure (2.0% versus 0.8%; p = 0.0072), and venous thromboembolism (1.7% versus 0.7%; p = 0.0122). There were no significant differences between the 2 groups in the incidence of abscess, urinary tract infection, dehiscence, cardiac complications, hemorrhage, neurologic complications, or peripheral nerve injury.
Frequency of 30-Day Adverse Outcomes in 5,420 Patients Who Underwent Open Resection or Laparoscopic-Assisted Proctectomy for Cancer
Patients who underwent open resection had a higher rate of intraoperative blood transfusion (12.3% versus 4.3%; p < 0.0001). Median LOS was 7 days (interquartile range 5 to 10) in the open group versus 5 days (interquartile range 4 to 8) in the LAP group (p < 0.0001). The frequency of prolonged LOS, defined as >10 days, was higher in the open group (20.1% versus 11.8%; p < 0.0001). There were no differences in the rates of 30-day reoperation or mortality between the 2 groups ().
Predictors of morbidity after proctectomy
The following preoperative variables were significantly associated with 30-day complication after proctectomy for cancer in univariate analysis: age, sex, race/ethnicity, body mass index, recent weight loss, functional status, smoking, diabetes mellitus, COPD, dyspnea, coronary artery disease, CHF, hypertension, peripheral vascular disease, neurologic disease, and chronic steroid use (). There was no association between alcohol use, bleeding disorder, or use of neoadjuvant therapy and 30-day morbidity.
Characteristics of Patients (n = 5,420) Who Underwent Proctectomy for Cancer and Did or Did Not Have a Postoperative Complication within 30 Days
Of the preoperative laboratory values, WBC count, hematocrit, platelet count, international normalized ratio, creatinine, SGOT, alkaline phosphatase, and albumin were significantly associated with morbidity in univariate analysis. Operative variables that had a significant association with postoperative complication included wound class, ASA class, blood transfusion, length of operation, ostomy creation, abdominoperineal resection, and open versus laparoscopic-assisted resection.
Variables that differed between the open and LAP groups at the p < 0.05 level in univariate analysis were used to construct a multivariable model of morbidity. This model also included the LAP propensity score variable, with indicators for quintiles, to adjust for nonrandom assignment of treatment. Logistic regression was used to calculate AOR and 95% confidence intervals for 30-day postoperative complications after proctectomy. Results of this analysis are displayed in . After adjusting for LAP propensity score and the other variables, age and sex were not significantly associated with one of the primary outcomes, 30-day morbidity. AOR of morbidity was higher in blacks compared with whites (AOR = 1.50; 95% CI, 1.18–1.92).
Adjusted Odds Ratios and 95% Confidence Intervals for 30-Day Complication after Proctectomy for Cancer
Compared with normal weight, obesity class I (AOR = 1.31; 95% CI, 1.08–1.58), class II (AOR = 1.47; 95% CI, 1.13–1.91), and class III (AOR = 1.53; 95% CI, 1.11–2.11) were all associated with morbidity. Weight loss of >10% of total body weight in the 6 months before surgery was also a risk factor for having a complication (AOR = 1.45; 95% CI, 1.13–1.86). Other comorbid conditions that were associated with morbidity included COPD (AOR = 1.72; 95% CI, 1.26–2.34), peripheral vascular disease (AOR = 2.23; 95% CI, 1.23–4.07), and chronic steroid use (AOR = 1.68; 95% CI, 1.02–2.77). The only preoperative laboratory variable that was significantly associated with morbidity was WBC count, where a low value (<4.5 × 103 cells/µL) was protective.
Operative variables that were associated with morbidity included ASA class 3 (AOR = 1.18, 95% CI, 1.02–1.36), APR (AOR = 1.20; 95% CI, 1.05–1.37), transfusion of >2 U blood (AOR = 1.68; 95% CI, 1.20–2.34), and duration of operation longer than 4 hours (AOR = 1.38; 95% CI, 1.20–1.58). Importantly, after adjusting for possible confounders and treatment propensity score, the type of resection was significantly associated with 30-day morbidity. Compared with LAP, the AOR of complication after open resection was 1.41 (95% CI, 1.19–1.68).
To confirm that there was a difference in risk-adjusted morbidity between the open resection and LAP groups, we determined 30-day complication rates after stratifying by LAP propensity score quintiles. Results of this analysis are displayed in and . In each propensity score quintile, the frequency of morbidity was lower in the LAP group compared with the open resection group. Differences were statistically significant for quintiles 2, 4, and 5.
Unadjusted 30-Day Complication Rates after Open Proctectomy or Laparoscopic-Assisted Proctectomy for Cancer, Stratified by Propensity Score Quintiles
Unadjusted 30-day complication rates after open proctectomy or laparoscopic-assisted proctectomy for cancer, stratified by propensity score quintiles. Solid line, open proctectomy; dotted line, laparoscopic-assisted proctectomy.