Received 27 March 2016; accepted 25 April 2016; published 28 April 2016
Resection of malignant pelvic tumors has long been considered to be associated with poorer outcomes and higher morbidity than resection of malignant limb tumors  -  . Although recent advances in perioperative management may have improved outcomes in pelvic tumor surgery, the availability of up-to-date data on mortality and morbidity is limited because these tumors are relatively rare. Data in previous studies were based on small sample sizes of fewer than 100 or obtained retrospectively over decades  -  . In the present study, we used a national inpatient database to compare in-hospital mortality and postoperative complications between primary malignant pelvic tumor surgery and primary malignant limb tumor surgery.
2. Patients and Methods
2.1. Data Source
The anonymous nature of the data allowed the requirement for informed consent to be waived. This study was approved by the Institutional Review Board of The University of Tokyo.
2.3. Patient Background Characteristics
Blood transfusion volume was categorized into 0, 1 - 999, 1000 - 2499, and ≥2500 ml. Duration of anesthesia was categorized into ≤119, 120 - 239, 240 - 359, 360 - 479, and ≥480 min. The DPC data do not include information on the duration of operation, but the duration of anesthesia generally reflects operative time  .
2.4. Outcome Measurements
The primary outcomes were in-hospital mortality and postoperative complications. Postoperative complications included acute renal failure (N17), venous thromboembolism (I80.0-I80.3, A40-A41, and D65), pneumonia (J12-J18), and surgical site infection (T813 and T814).
2.5. Statistical Analysis
Univariable comparisons of the outcomes between the subgroups for individual patient characteristics were conducted using the chi-square test. A logistic regression analysis was performed to analyze the concurrent effects of various factors on the occurrence of postoperative complications, while adjusting for clustering of patients within hospitals using a generalized estimating equation  . The threshold for significance was set at p < 0.05. All statistical analyses were conducted using IBM SPSS version 19.0 (IBM SPSS, Armonk, NY, USA).
The patient background characteristics are shown in Table 1. We identified 3255 eligible patients (1740 men and 1515 women; mean age (±standard deviation), 59.5 ± 18.8 years), consisting of 3116 patients with primary malignant limb tumor surgery and 139 patients with primary malignant pelvic tumor surgery. Sixty-three patients were excluded from the logistic regression analysis owing to lack of data about duration of anesthesia. Patients with pelvic tumors were more likely to receive blood transfusion (54.7%) than those with limb tumors (13.8%) (p < 0.001). More patients undergoing pelvic tumor surgery required longer duration of anesthesia (>480 min) than patients undergoing limb tumor surgery (34.5% vs 9.1%). The demographic patterns of the tumor sites and surgical procedures are shown in Table 2.
The in-hospital mortality and postoperative complications for each category are shown in Table 3. In-hospital mortality for pelvic tumor surgery was comparable to that for limb tumor surgery (0.6% vs 0.7%, p = 0.830). The incidence of postoperative complications following pelvic tumor surgery was two-fold higher than that following limb tumor surgery. Duration of anesthesia, use of blood transfusion, and volume of blood transfusion were associated with higher in-hospital mortality and postoperative complication rate. Of note, patients who required blood transfusion of more than 2500 ml were more likely to have postoperative complications than those who did not (44.6% vs 6.5%, p < 0.001). Similarly, patients with duration of anesthesia over 480 min were more likely to have postoperative complications than those who did not (25.0% vs 6.6%, p < 0.001).
Table 4 shows the results of logistic regression analyses for perioperative complications. Pelvic tumor surgery showed no significant differences for postoperative complications compared with primary limb tumor surgery (odds ratio, 0.96; 95% confidence interval, 0.60 - 1.55; p = 0.869). A higher complication rate was significantly associated with higher volume of blood transfusion, distant metastasis, and longer duration of anesthesia. In particular, patients with blood transfusion volumes greater than 2,500 ml and those with duration of anesthesia longer than 480 min showed high odds ratios for postoperative complications (≥2500 ml: 3.69; ≥480 min: 6.11).
In this study, we used a Japanese nationwide inpatient database to compare the in-hospital mortality and postoperative complications of patients who underwent surgery for primary malignant musculoskeletal tumors of the pelvis and limbs. Our results indicate that increased risks in pelvic tumor surgery was largely attributable to major intraoperative bleeding requiring blood transfusion and long operation time requiring long duration of anesthesia.
The occurrence of postoperative complications following pelvic tumor surgery was twice as high as that following limb tumor surgery. Of note, patients who underwent pelvic tumor surgery were six-fold more likely to receive a blood transfusion volume greater than 2500 ml that those who underwent limb surgery. After adjusting for confounding variables, including the volume of blood transfusion, we found that the risk of perioperative complications did not differ between pelvic and limb tumor surgery. Our results indicate that the increased risk for pelvic tumor surgery was largely attributable to major intraoperative bleeding requiring blood transfusion. This finding is consistent with those in previous reports   , although the referred papers reported only external hemipelvectomy. Our data indicated similar tendency in postoperative complications both in external and
Table 1. Patient background characteristics.
Table 2. Demographic patterns of tumor sites and surgical procedures.
Our results indicate that another increased risk in pelvic tumor surgery was largely attributable to long operation time requiring long duration of anesthesia. There are clear associations between longer duration of anesthesia or operation time and postoperative complications in various medical settings  -  . Shortening of the operation time was also important for musculoskeletal tumor resection. Therefore, to reduce complications after musculoskeletal malignant tumor resection, we should strive to decrease the operation time.
Our study has several limitations inherent to all administrative database studies. First, the DPC database does not provide important clinical data, such as pathological data of each case, tumor volume, individual chemotherapy
Table 3. In-hospital mortality and postoperative complications.
regimens and dosage of each agent, and details of surgical procedures such as type of pelvic resection or instrumentation used for limb salvage. Second, the DPC database is restricted to information on in-hospital and major complications only and does not provide any information pertaining to those before admission and after discharge. Third, the DPC database provides epidemiological and broad data. Thus, precise and extensive analysis
Table 4. Logistic regression analyses for postoperative complications.
is difficult for the DPC database study.
Our data demonstrated that a larger blood transfusion volume and longer operative time were significantly associated with worse outcomes. The higher morbidity rate after pelvic tumor resection could result from the larger blood transfusion volume and longer anesthesia duration. We need to decide carefully whether to carry out surgical treatment with consideration of the risk and benefit of each candidate treatment plan, in cases with expectations of larger volume of blood transfusion and longer operative time.
This study was supported by a Grant-in-Aid for Research on Policy Planning and Evaluation from the Ministry of Health, Labour and Welfare, Japan (grant number: H26-Policy-011).
The authors declare that they have no competing interests.
DPC: Diagnosis Procedure Combination.