Expected Survival Curves Research Articles

Long-term survival of patients with stage II and III gastric cancer who underwent gastrectomy with inadequate nodal assessment.

BACKGROUNDGastric cancer is an aggressive disease with frequent lymph node (LN) involvement. The NCCN recommends a D2 lymphadenectomy and the harvesting of at least 16 LNs. This threshold has been the subject of great debate, not only for the extent of surgery but also for more appropriate staging. The reclassification of stage IIB through IIIC based on N3b nodal staging in the eighth edition of the American Joint Committee on Cancer (AJCC) staging system highlights the efforts to more accurately discriminate survival expectancy based on nodal number. Furthermore, studies have suggested that pathologic assessment of 30 or more LNs improve prognostic accuracy and is required for proper staging of gastric cancer.AIMTo evaluate the long-term survival of advanced gastric cancer patients who deviated from expected survival curves because of inadequate nodal evaluation.METHODSEligible patients were identified from the Surveillance, Epidemiology, and End Results database. Those with stage II–III gastric cancer were considered for inclusion. Three groups were compared based on the number of analyzed LNs. They were inadequate LN assessment (ILA, < 16 LNs), adequate LN assessment (ALA, 16-29 LNs), and optimal LN assessment (OLA, ≥ 30 LNs). The main outcomes were overall survival (OS) and cancer-specific survival. Data were analyzed by the Kaplan-Meier product-limit method, log-rank test, hazard risk, and Cox proportional univariate and multivariate models. Propensity score matching (PSM) was used to compare the ALA and OLA groups.RESULTSThe analysis included 11607 patients. Most had advanced T stages (T3 = 48%; T4 = 42%). The pathological AJCC stage distribution was IIA = 22%, IIB = 18%, IIIA = 26%, IIIB = 22%, and IIIC = 12%. The overall sample divided by the study objective included ILA (50%), ALA (35%), and OLA (15%). Median OS was 24 mo for the ILA group, 29 mo for the ALA group, and 34 mo for the OLA group (P < 0.001). Univariate analysis showed that the ALA and OLA groups had better OS than the ILA group [ALA hazard ratio (HR) = 0.84, 95% confidence interval (CI): 0.79–0.88, P < 0.001 and OLA HR = 0.73, 95%CI: 0.68–0.79, P < 0.001]. The OS outcome was confirmed by multivariate analysis (ALA HR = 0.68, 95%CI: 0.64–0.71, P < 0.001 and OLA: HR = 0.48, 95%CI: 0.44–0.52, P < 0.001). A 1:1 PSM analysis in 3428 patients found that the OLA group had better survival than the ALA group (OS: OLA median = 34 mo vs ALA median = 26 mo, P < 0.001, which was confirmed by univariate analysis (HR = 0.81, 95%CI: 0.75–0.89, P < 0.001) and multivariate analysis: (HR = 0.71, 95%CI: 0.65–0.78, P < 0.001).CONCLUSIONProper nodal staging is a critical issue in gastric cancer. Assessment of an inadequate number of LNs places patients at high risk of adverse long-term survival outcomes.

Survival of South African children with cerebral palsy.

The South African (SA) public healthcare sector has experienced a surge in birth injury claims in recent years, particularly in respect of cerebral palsy (CP). The lump sum settlements in these matters are a function of the expected survival curve of the individual concerned. It is known from international studies that the life expectancy of children with CP is shorter than that of the general population, and depends on the pattern and severity of their disabilities. However, empirical estimates of survival for children with CP in SA are not available. To construct survival curves according to the pattern of gross motor skills for CP children in SA and compare these with international studies. We collected data on mortality and functional status for 339 CP childrenon whose behalf claims for medical negligence had been instituted. Motor disabilities were classified according to the five-level Gross Motor Function Classification System (GMFCS). Children who were unable to walk unaided were further classified according to more basic motor skills, including the ability to lift their heads or chests in the prone position, rolling and sitting. Mortality rates were calculated and survival curves were estimated using the Kaplan-Meier method. No deaths were observed among 119 children in GMFCS levels I - IV. Among the 220 children in GMFCS V, there were 20 observed deaths. The proportions surviving to ages 10 and 15 years were 85% (standard error (SE) 5%) and 55% (SE 11%), respectively. The former is comparable to what has been reported for children in California and Sweden, but the survival to age 15 is lower. Among 82 children who could not lift their heads in the prone position, there were 11 observed deaths for a mortality rate of 48.5 (95% confidence interval (CI) 24.2 - 86.9) deaths per 1 000 person-years. Among 72 children who could lift their heads but not their chests, there were 6 observed deaths for a mortality rate of 33.5 (95% CI 12.3 - 73.0) deaths per 1 000 person-years. These mortality rates are 22% and 15% higher than the corresponding figures documented for children with comparable abilities and disabilities in California. Life expectancy of children with CP in SA is lower than that of children with comparably severe disabilities in high-income countries.

A Bayesian CUSUM plot: Diagnosing quality of treatment.

To present a CUSUM plot based on Bayesian diagnostic reasoning displaying evidence in favour of "healthy" rather than "sick" quality of treatment (QOT), and to demonstrate a technique using Kaplan-Meier survival curves permitting application to case series with ongoing follow-up. For a case series with known final outcomes: Consider each case a diagnostic test of good versus poor QOT (expected vs. increased failure rates), determine the likelihood ratio (LR) of the observed outcome, convert LR to weight taking log to base 2, and add up weights sequentially in a plot showing how many times odds in favour of good QOT have been doubled. For a series with observed survival times and an expected survival curve: Divide the curve into time intervals, determine "healthy" and specify "sick" risks of failure in each interval, construct a "sick" survival curve, determine the LR of survival or failure at the given observation times, convert to weights, and add up. The Bayesian plot was applied retrospectively to 39 children with acute lymphoblastic leukaemia with completed follow-up, using Nordic collaborative results as reference, showing equal odds between good and poor QOT. In the ongoing treatment trial, with 22 of 37 children still at risk for event, QOT has been monitored with average survival curves as reference, odds so far favoring good QOT 2:1. QOT in small patient series can be assessed with a Bayesian CUSUM plot, retrospectively when all treatment outcomes are known, but also in ongoing series with unfinished follow-up.

Long-Term Outcomes Comparison of Mitral Valve Replacement Versus Repair in Elderly Patients

Objective: To compare survival and postoperative valve durability following mitral valve replacement and repair (MVR/r) in patients > 70 years-old in order to better inform optimal operative decision-making. Methods: All patients undergoing MVR/r at our institution since 1960 have been prospectively followed for survival and explant on an annual basis. Expected survival was calculated for each patient from age-gender-operative year-matched US life tables. Observed and Expected survival curves were plotted and compared using Standardised Mortality Ratio (SMR = total observed deaths/total expected deaths). The cumulative incidence function (CIF) was used to determine valve explant rates at 12 years. Results: There were 771 patients > 70 years of age at time of isolated MVR/r (1971-2015) with 5,126 patient-years of follow-up. The survival and explant outcomes of all mitral repairs (MVr, 375) and MVR with mechanical (170), porcine (118) and pericardial (103) implants were compared. There were no significant differences in age, gender or incidence of CABG. Observed survival for porcine and mechanical MVR was very much worse than expected (SMR = 2.0 and 1.7 respectively, p < 0.001 for both); slightly worse than expected for MVr (SMR = 1.16; 95%CI = 1.02-1.37); whereas survival following pericardial MVR was equal to expected (SMR = 1.2; 95%CI = 0.89-1.75). However, the cumulative incidence of redo mitral surgery or prosthetic valve explant at 14 years was 0% for pericardial MVR, which is equal to (significantly LESS THAN) mechanical MVR (2%), but significantly lower than that for mitral repair (8%) and porcine MVR (7.5%). Conclusions: In patients > 70 years old, mitral repair, mechanical MVR and porcine MVR do not restore expected survival, whereas pericardial MVR restores expected survival. However the incidence of redo mitral surgery following MVr is significantly higher than that following pericardial MVR. These data suggest that the long-term outcomes of pericardial MVR may be superior to native MVr for patients > 70 years old, as pericardial MVR both preserves survival and minimises reoperation.

Review of Case-Mix Corrected Survival Curves

Survival is an end point of immense interest in cardiothoracic research. In observational studies, the comparison of survival between groups of patients is usually accomplished using a toolbox that includes Kaplan-Meier survival curves and the Cox model. The Cox model yields comparisons between groups adjusted for case-mix differences, whereas the Kaplan-Meier is a plot of survival over time without adjustment. During the past decade, new methods have emerged for case-mix adjustment of survival curves and are increasingly being used in cardiothoracic research. The purpose of this report is to describe, illustrate, and review several approaches to case-mix adjusted survival (or event-free) curves.

Validation of a cholangiographic prognostic model in primary sclerosing cholangitis

We previously developed a prognostic model for primary sclerosing cholangitis (PSC), which was primarily based on a cholangiographic classification of the intra- and extrahepatic biliary tree lesions. The aim of the present study was to validate the performance of this model in an external cohort. The validation dataset consisted of patients with PSC from a single referral center in Oslo, Norway. The patients' cholangiograms were scored according to the Amsterdam classification. We then examined whether adjusting the value of the original coefficients of the predictors or adding new predictors would improve the fit of the original model in the validation cohort. In addition, we evaluated calibration (closeness between observed and expected survival) and discrimination using the concordance index. A total of 111 patients (mean age 35 +/- 13 years; 76 % male) were included in the validation study. Baseline clinical characteristics were comparable between the two cohorts. None of the coefficients that were re-estimated in the validation cohort differed significantly from the values of the original model. Observed and expected survival curves were in close agreement across different risk groups. Discrimination of the original model was preserved in the validation cohort: the concordance index was the same in both cohorts. The prognostic model showed adequate performance in an independent series of patients. Therefore, we updated the model using the data from both cohorts to provide more robust estimates of transplant-free survival for individual patients. A nomogram was constructed, which can be used to predict medium- and long-term prognosis in individual patients with PSC.

Octogenarian Abdominal Surgical Emergencies: Not So Grim a Problem With the Acute Care Surgery Model?

As the aging population continues to increase, the surgical needs of the elderly will increase. The acute care surgery model has been developed in which the trauma team also manages all general surgical emergencies to improve patient outcomes. We retrospectively reviewed our elderly acute care surgery population during the past 5 years to determine the variables affecting major abdominal surgery outcomes. Patients aged 80 years and older who received an emergent major abdominal operation by our Acute Care Surgery team between July 2000 and November 2006 were included. We assessed after-hours operations, length of stay, duration of operation, gender, comorbidities, and mortality. Administrative, operating room, and corporate databases were used for demographics, comorbidities, admission logistics, American Society of Anesthesiologists (ASA) score, and mortality. We performed SPSS, chi2, and logistic regression analyses. A total of 183 operations were performed with a mortality of 15%. Significant predictors were ASA score and female gender, with increasing ASA scores leading to worse outcomes and women faring worse than men as an independent variable. Neither operative duration nor off-hours surgery was associated with increased mortality. This is the first study to report mortality data and expected survival curves for major abdominal surgery in the octogenarian population. Our data prove that it is safer than previously thought to operate on the elderly. Our mortality data and survival curves provide real data for the surgeon to be able to risk stratify and discuss predicted outcomes with consultants, patients, and families.

Application of a biochemical and clinical model to predict individual survival in patients with end-stage liver disease

To investigate the capability of a biochemical and clinical model, BioCliM, in predicting the survival of cirrhotic patients. We prospectively evaluated the survival of 172 cirrhotic patients. The model was constructed using clinical (ascites, encephalopathy and variceal bleeding) and biochemical (serum creatinine and serum total bilirubin) variables that were selected from a Cox proportional hazards model. It was applied to estimate 12-, 52- and 104-wk survival. The model's calibration using the Hosmer-Lemeshow statistic was computed at 104 wk in a validation dataset. Finally, the model's validity was tested among an independent set of 85 patients who were stratified into 2 risk groups (low risk <or= 8 and high risk > 8). In the validation cohort, all measures of fit, discrimination and calibration were improved when the biochemical and clinical model was used. The proposed model had better predictive values (c-statistic: 0.90, 0.91, 0.91) than the Model for End-stage Liver Disease (MELD) and Child-Pugh (CP) scores for 12-, 52- and 104-wk mortality, respectively. In addition, the Hosmer-Lemeshow (H-L) statistic revealed that the biochemical and clinical model (H-L, 4.69) is better calibrated than MELD (H-L, 17.06) and CP (H-L, 14.23). There were no significant differences between the observed and expected survival curves in the stratified risk groups (low risk, P = 0.61; high risk, P = 0.77). Our data suggest that the proposed model is able to accurately predict survival in cirrhotic patients.

Predicting Individual Survival After Potentially Curative Esophagectomy for Adenocarcinoma of the Esophagus or Gastroesophageal Junction

Even after potentially curative esophagectomy, the majority of patients with adenocarcinoma of the esophagus or gastroesophageal junction die due to cancer recurrence. To predict individual disease-specific survival, a nomogram has been developed in a high-volume center in the Netherlands. The validity of this nomogram was externally tested in patients treated in another country at a different high-volume institution. Clinicopathological data from patients who underwent a macroscopically radical resection in a high-volume center in Leuven, Belgium, were used to validate the original nomogram based on a Cox regression model. Moreover, it was examined whether adjusting the value of the original coefficients of the predictors or adding new predictors would improve the fit of the nomogram in the validation cohort. Calibration was evaluated by comparing the observed survival with the expected survival as predicted by the original nomogram across patients with different risk profiles. The discriminatory ability of the nomogram was determined in the validation cohort, using the concordance index and compared with the original estimate. A total of 382 patients were used in the validation study. The median esophageal cancer-specific survival was 38 months. None of the coefficients re-estimated in the validation cohort differed significantly from the values of the original nomogram. Observed and expected survival curves showed good calibration. Discrimination of the original nomogram was preserved in the validation cohort: the concordance index hardly decreased from 0.77 in the original cohort to 0.76 in the validation cohort. The nomogram model that was originally developed in a Dutch institute had good individual discriminatory properties and good overall calibration when applied to an independent series of patients. The nomogram was updated using the data from both cohorts to provide even more robust estimates of survival for individual patients. This tool is clinically helpful to supply more reliable prognostic information, to offer tailored follow-up schedules and/or novel therapeutic strategies in subgroups of patients with higher risk of recurrence.

Efficacy of primary hormone therapy for localized or locally advanced prostate cancer: results of a 10‐year follow‐up

To evaluate the efficacy of primary hormone therapy for localized or locally advanced prostate cancer, by analysing the 10-year survival rates for men with localized or locally advanced prostate cancer treated with primary hormone therapy or prostatectomy. Between February 1993 and March 1995, men with T1b, T1c or T2-3 N0M0 prostate cancer were enrolled. In all, 176 men who had a prostatectomy were assigned to Study 1 and were given adjuvant luteinizing hormone-releasing hormone (LHRH) agonist; 151 men who did not have a prostatectomy were assigned to Study 2 and had LHRH agonist monotherapy or combined androgen blockade. They were followed until death, loss to follow-up, or until the end of the observation period (31 March 2004). We analysed all cases in each study as a single population, and compared Study 1 with Study 2. The mean patient ages were 67.2 years in Study 1 and 75.7 years in Study 2. During a median of 10.4 years of follow-up, 20 men in Study 1 and 17 in Study 2 died from prostate cancer, and 21 men in Study 1 and 50 in Study 2 died from other causes. In Study 1, the 10-year overall survival rate was 73% and the 10-year cause-specific survival rate was 86%, vs 41% and 78% in Study 2. Overall survival curves were similar to expected survival curves in both studies. There was no significant difference between studies in cause-specific survival. The progression of prostate cancer was retarded by primary hormone therapy in men with localized or locally advanced prostate cancer. With primary hormone therapy or prostatectomy, the men had a life-expectancy similar to that of the normal population.

Miocardiopatía hipertrófica en el adulto. Curso clínico y factores pronósticos de 119 pacientes

The purpose of this study was to characterize adult patients with hypertrophic cardiomyopathy (HCM), to compare their mortality with that of the general population and to establish a prognosis based on clinical and noninvasive techniques. One hundred nineteen consecutive patients (60 women, mean: 52 [12] years) with HCM were prospectively studied by ECG, Holter, echo-Doppler, exercise testing, myocardial perfusion SPET and radionuclide ventriculography. Prognostic variables included clinical data and parameters derived from these noninvasive techniques. During a mean follow-up of 10 [6.7] years, 7 patients (5.8%) died of cardiovascular causes (4 cardiac failure and 3 sudden death). The annual mortality rate was 0.6% and the actuarial survival curve for patients with HCM was significantly worse compared with the expected survival curve derived from the general population after adjustment for age and sex (p = 0.008). The presence of atrial fibrillation (p = 0.04), moderate or severe mitral regurgitation (p = 0.02), dynamic gradient > 50 mmHg (p = 0.02), left atrial diameter > 45 mm (p = 0.02), and interventricular septal thickness > 25 mm (p = 0.04) were all predictive of mortality. The mortality rate of adult patients with HCM is significantly higher than that expected for the general population and heart failure and sudden death are almost evenly distributed as a cause of death in these patients. Atrial fibrillation, magnitude of mitral regurgitation, dynamic gradient, left atrial dilatation and interventricular septal thickness are the main predictors of death.

Radiotherapy after surgery for benign cerebral meningioma

Background and purpose To compare the outcome from adjuvant and delayed radiotherapy (RT) after surgery in patients with benign cerebral meningioma. Patients and methods Between March 1953 and January 2001, 92 patients with benign cerebral meningioma (WHO grade I) were treated with surgery. Forty-eight patients underwent gross total resection (GTR), and 44 patients underwent subtotal resection (STR). Treatments were classified as GTR ( n=48), STR+adjuvant RT ( n=12), STR alone ( n=32). The prognostic factors were assessed as, gender, the Karnofsky performance score (KPS) (≥90 vs. <90), the extent of surgery, and adjuvant or delayed RT. The endpoints analyzed were progression-free survival (PFS) and overall survival (OS). Overall survival curve of the study population is compared with the age-adjusted expected survival curve for the US population born in 1970. Results The median follow-up was 7.7 years. The 5-year PFS and OS rates for all patients were 65 and 93%, respectively. The 5-year PFS rates in patients treated with GTR and STR were 77 and 52%, respectively ( P=0.02). Patients treated with STR+adjuvant RT had significantly better PFS (91%) at 5 years than with STR alone (38%) ( P=0.0005). Gender showed no statistically significant impact on either PFS or OS ( P>0.05). However, multivariate analysis showed the KPS to have a statistically significant effect on OS ( P=0.02). The OS rate was the same across all three treatment groups. The age-adjusted expected survival curve for the US population born in 1970 lay within the confidence intervals for the overall survival curve of the study population. Conclusions Although OS was not affected, adjuvant RT appeared to significantly reduce tumor progression. However, only a prospective randomized trial can adequately determine whether adjuvant or delayed radiotherapy is the better approach in patients with subtotally resected benign meningioma.

Using the expected survival to explain differences between the results of randomized trials: a case in advanced ovarian cancer.

A meta-analysis of randomized trials in advanced ovarian cancer showed a longer survival with cyclophosphamide, doxorubicin, and cisplatin (CAP) than with cyclophosphamide and cisplatin (CP; P =.009). In contrast, the results of the large International Collaborative Ovarian Neoplasm Study (ICON2) showed no survival difference between CAP and carboplatin (P =.98). In this article, we show how these discrepant results can be reconciled through the estimation of expected survival curves. A proportional hazards model, fitted to the meta-analysis data, was used to construct the expected survival curve for each treatment arm of the ICON2 trial. Expected survival curves were compared with observed survival curves in the ICON2 trial at all time points using a nonparametric test. The prognostic model for survival obtained in the meta-analysis included extent of residual disease, age, histologic grade, and International Federation of Gynecology and Obstetrics stage. When this model was applied to the ICON2 data, there was no difference between the expected and observed curves in the CAP arm. In contrast, the observed survival curve for carboplatin was far superior to the expected survival curve for CP (P <.01). These analyses provide indirect evidence that better results are achieved with carboplatin alone at an optimally tolerated dose, compared with the CP combination at a cisplatin dose of 50 to 60 mg/m2. The expected survival may provide valuable insight when direct comparisons between randomized groups yield discrepant results across different studies.

Evaluating inter‐hospital variability in mortality rates over time, allowing for time‐varying effects

In outcome studies, quality of care in various institutions is typically assessed by comparing observed to expected outcome rates, after adjusting for patients' case-mix factors in logistic regression models. However, differences in patterns of outcome rates over time, especially when there is a distinction between the determinants affecting early and later events, are rarely studied. We use six-month mortality after coronary artery bypass graft operation (CABG) as an example. We present a statistically valid approach to estimate expected survival curves for different subgroups, based on a Cox survival model with time-varying effects. Bootstrap confidence intervals around the expected survival curves are constructed. This approach is applied for examining the pattern of deviation of high-mortality hospitals after CABG. Implications for quality assessment in comparative outcome studies are discussed.

Expected survival compared with survival of peptic ulcer patients

In analyses of patient survival it is often desirable to compare observed survival curves with expected survival curves based on information obtained from the general population. However, current methods of calculating expected survival curves are difficult to interpret and are often poorly documented. We discuss an alternative formulation of the so-called direct method which we recommend for general use. By simulation, we show that the expected survival curve obtained from this method represents the expectation of a Kaplan–Meier curve for a set of random population controls. Thus, the term expected survival does not refer to the expectation of patient survival, but rather to the expected survival curve for a random set of controls. The alternative methods are discussed, and we illustrate the methods in an analysis of long time survival of a population-based sample of peptic ulcer patients. © 1998 John Wiley & Sons, Ltd.

Expected Survival in the Cox Model

The survival in a group of patients is calculated using a Kaplan–Meier curve and the hypothesis that the survival can be predicted by a specified Cox hazard is studied. This Cox hazard is obtained from a previous study of similar patients. A simple test of the hypothesis is constructed by comparing a suitable average of the individual predicted survival curves with the observed survival. Three averaging procedures are presented; “direct adjusted survival curve”, “Bonsel’s survival curve” and “expected survival curve”. Consistency and asymptotic distribution properties of the comparisons are discussed.

A note on the calculation of expected survival, illustrated by the survival of liver transplant patients

Based on historical regression analyses of survival one may calculate expected survival curves for patients in a study group, based on their observed covariates. This note discusses this calculation and illustrates it on a comparison of the survival of a certain group of liver transplant patients to their prognosis under conservative treatment.

Survival after Liver Transplantation of Patients with Primary Biliary Cirrhosis in the Nordic Countries Comparison with Expected Survival in Another Series of Transplantations and in an International Trial of Medical Treatment

Until December 1988, 38 patients with primary biliary cirrhosis (PBC) had been transplanted in the Nordic countries. The observed survival probability in accordance with Kaplan-Meier analysis was around 75% 2-3 months after surgery, with few deaths during the next 3 years. The observed survival curve was compared with the expected survival calculated from the experience of a recent English PBC transplant series; the patterns are very similar. Secondly, the observed survival was compared with the expected survival curve, calculated from the survival experience of an international trial of medical treatment--that is, the expected survival had the patients not been transplanted; after the first 2-3 months the observed survival stayed better than the expected survival. Finally, the merits of transplantation for each particular patient was evaluated by means of the ratio of probability of survival when transplanted to probability of survival when medically treated 3, 6, and 8 months after surgery. The ratio increased with time, indicating a relative increase in the benefit of transplantation with time after surgery.

The curability of breast cancer.

AbstractA long‐term follow‐up study was performed of 704 women who were treated for breast cancer during 1947–50 at Addenbrooke's Hospital, Cambridge, England. After 21 years the observed survival curve for the treated patients and the expected survival curve for the normal population became parallel, suggesting a “cure rate” of about 18% for all cases of breast cancer and about 30% for cancers in stages I and II combined. At least 6 patients died of breast cancer after 20 years. Eighty‐one patients survived for 20 or more years, and at least 21 of these originally had metastases in axillary lymph nodes. It would be very worthwhile if this “curable” group could be identified at the time of diagnosis so that they would be spared systemic adjuvant treatments.

Course and prognosis of Crohn's disease.

During the period 1938-70 there were 303 patients at the Radcliffe Infirmary, Oxford, diagnosed as suffering from Crohn's disease. Of these, 82 have been excluded, leaving 221 with a firm diagnosis. These patients have been divided into 'new cases', in which the disease was diagnosed at the Radcliffe Infirmary, and 'referred cases' in which the diagnosis was already made at the time of referral. In this series, there were three main sites of involvement: small intestinal, large intestinal, and both small and large intestinal. Ileocolitis was the commonest anatomical distribution. The disease showed progression to new, sites in a considerable number of the patients during the period under study. There was a fivefold increase of new cases between the first and third decades covered by the study and this applied equally to patients presenting as an acute abdomen, which supports the idea that the disease is truly increasing. Survival curves have been plotted and compared with expected survival curves. In terms of mortality, Crohn's disease emerges as a disease which becomes progressively more dangerous as the years go by, which is in sharp contrast with the findings in ulcerative colitis in which the main risk of dying is in the early years.