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Esophageal cancer treatment statistics and results

When you are told you have esophageal cancer and begin looking for treatment options, you may be concerned about life expectancy and quality of life. At Cancer Treatment Centers of America® (CTCA), we believe you have the right to know our statistics for esophageal cancer treatment outcomes, so you can choose the best cancer care for you and your family.

ctca statistics and results

Esophageal cancer survival statistics and results

Survival Results: Esophageal Cancer

At Cancer Treatment Centers of America® (CTCA), we understand that you may want to see information regarding the survival results of patients with metastatic esophageal cancer who were diagnosed and/or at least partly treated at our hospitals to help you and your family decide where to go for treatment, as part of many other factors you may be considering. Therefore, we asked an independent biostatistician to analyze the survival results of CTCA® patients.

The chart below shows the cancer survival rates for a group of 77 metastatic esophageal cancer patients who were diagnosed between 2000 and 2009. Each patient in the group was first diagnosed at CTCA and/or received at least part of their initial course of treatment at CTCA.

esophageal survival ctca 5yr vertical
 

Of the CTCA metastatic esophageal cancer patients shown in the above chart, the estimated survival rate at six months was 62%. This means that six months after their diagnosis, 62% of the patients in this group were still living.

CTCA and SEER Survival Analysis

At Cancer Treatment Centers of America, we understand that you may also wish to see the survival rates of the group of metastatic esophageal cancer patients reported in the Surveillance, Epidemiology and End Results (SEER) database of the National Cancer Institute. SEER is a source of population-based information about cancer incidence and survival in the United States that includes the stage of cancer at the time of diagnosis and patient survival data. SEER collects information on cancer incidence, prevalence and survival from specific geographic areas that represent 28% of the population of the United States. It then makes this data available through its database at seer.cancer.gov.

Therefore, we asked an independent biostatistician to analyze both the survival rates of the group of CTCA patients and the group of patients included in the SEER database.

The objective of this analysis was to see how long each group of patients survived after their diagnosis. The results are shown in the chart below.

esophageal survival ctca seer 5yr vertical
 

In the case of metastatic esophageal cancer, 62% of CTCA patients who were diagnosed between 2000 and 2009 and/or at least partly treated at our hospitals survived for six months after the initial diagnosis, while 52% of the SEER metastatic esophageal cancer patients survived for at least that long.

How the Samples Were Chosen for the Analysis

The CTCA sample included all eligible cancer patients from four of our five cancer registries, including CTCA at Southwestern Regional Medical Center in Tulsa, Oklahoma; CTCA at Midwestern Regional Medical Center in Zion, Illinois; CTCA at Eastern Regional Medical Center in Philadelphia, Pennsylvania; and CTCA at Western Regional Medical Center in Goodyear, Arizona. Our fifth hospital, located near Atlanta, Georgia, was not included because it was not open to patients until August 2012.

“Eligible” patients were those who were first diagnosed at a CTCA cancer center between 2000 and 2009 (including 2000 and 2009) and/or received at least part of their initial course of treatment at a CTCA cancer center. Across all 11 cancer types for which survival results are presented on the CTCA website, 0.48% of the CTCA patients included in the analyses were diagnosed by CTCA, but received no initial course of treatment from CTCA. A similar statistic for each individual type of cancer included in the analysis is not currently available.

The independent biostatistician computed the survival outcomes of metastatic esophageal cancer patients from the CTCA database and metastatic esophageal cancer patients from the SEER database who were diagnosed between 2000 and 2009. In both cases, the patients had been diagnosed with metastatic (distant) cancer – cancer that had traveled from the primary site (esophagus) to one or more distant sites in the body where it continued to grow.

The CTCA sample is relatively small because only metastatic esophageal cancer patients who had been initially diagnosed at CTCA and/or received at least part of their initial course of treatment at CTCA were included. These factors significantly reduced the size of the CTCA sample, which means that the estimates reflected in the survival chart may be subject to high variation and may not be replicated in the future when we have a larger CTCA sample for analysis.

For a full, technical explanation of the methodology used in the analysis and a detailed description of the CTCA and SEER patient groups included , click on the Statistical Methodology: Esophageal Cancer tab above, and for more information about the SEER program, go to seer.cancer.gov.

We also want to be sure you understand that cancer is a complex disease and each person’s medical condition is different; therefore, CTCA makes no claims about the efficacy of specific treatments, the delivery of care, nor the meaning of the CTCA and SEER analysis. Not all cancer patients who are treated at a CTCA hospital may experience these same results.

* The SEER data represent national results over a large number of institutions and have been included for illustrative purposes. They are not intended to represent a controlled study and/or a perfect analysis of the CTCA and SEER data because of variability in the sample sizes of the two data bases, the clinical condition(s) of the patients treated, and other factors.

Statistical Methodology: Esophageal Cancer

An independent biostatistician analyzed the survival results of patients from the latest available SEER cancer database (as of 2012) and those who were initially diagnosed at CTCA and/or received at least part of their initial course of treatment at CTCA (i.e., the analytic cases). The statistical methodologies the biostatistician used in the analysis are described below:

1. Inclusion/exclusion criteria for patients from the CTCA cancer registry

This analysis included esophagus cancer patients from CTCA who were diagnosed from 2000 to 2009 (including 2000 and 2009) with primary tumor sites (as coded by ICD-O-2 (1973+)) from C150 to C159, and were considered the analytic cases by CTCA.

Patients who had a missing value for any of the following parameters were excluded from the analysis:

  • Cancer stage as assessed by either the 1977 SEER Summary Stages (SSS, see http://www.seer.cancer.gov/tools/ssm/) (for diagnostic year 2000) or the 2000 SEER Summary Stages (for diagnostic years from 2001 to 2003) or the Derived 2000 SEER Summary Stages (for diagnostic years from 2004 to 2009).

  • Primary tumor sites (as coded by ICD-O-2 (1973+)), date of initial diagnosis, date of last contact, year of initial diagnosis, age of initial diagnosis, gender, vital status, and cancer histologic type as coded by the ICD-O-3.

The CTCA database was prepared by the CTCA cancer registrars from the following four hospitals: Southwestern Regional Medical Center hospital (Tulsa), Midwestern Regional Medical Center hospital (suburban Chicago), Eastern Regional Medical Center hospital (Philadelphia), and Western Regional Medical Center hospital (suburban Phoenix). CTCA’s newest hospital near Atlanta, Georgia, was not included in the analysis because it was not open to patients until August 2012.

2. Inclusion/exclusion criteria for patients from the SEER cancer database

The SEER program of the National Cancer Institute is an authoritative source of information on cancer incidence and survival in the United States. SEER began collecting data on cancer cases on January 1, 1973. The SEER Program is a comprehensive source of population-based information in the United States that includes stage of cancer at the time of diagnosis and patient survival data.

This analysis included esophageal cancer patients from the latest SEER Limited-Use Database (as of 2012) who were diagnosed from 2000 to 2009 (including 2000 and 2009) with primary tumor sites (as coded by ICD-O-2 (1973+)) from C150 to C159.

Patients from the SEER database who had a missing value for any of the following parameters were excluded from the analysis:

  • Cancer stage as assessed by either the 1977 SEER Summary Stages (SSS, see http://www.seer.cancer.gov/tools/ssm/) (for diagnostic year 2000) or the 2000 SEER Summary Stages (for diagnostic years from 2001 to 2003) or the Derived 2000 SEER Summary Stages (for diagnostic years from 2004 to 2009).

  • Primary tumor sites (as coded by ICD-O-2 (1973+)), survival time recode as calculated by the date of initial diagnosis and the date of death or the follow-up cutoff date, year of initial diagnosis, age of initial diagnosis, gender, vital status, and cancer histologic type as coded by the ICD-O-3.

3. Matching criteria to select patients from the CTCA and the SEER databases

In order to make a meaningful survival analysis, basic cancer and patient characteristics such as age at initial diagnosis, year of initial diagnosis, cancer stages, cancer primary sites, and gender were first analyzed for both the CTCA and SEER samples. The final survival analysis included only patients whose following cancer characteristics are shared between the two databases:

  • SEER Summary Stages
  • Primary tumor sites
  • Cancer histologic types
  • Gender
  • Age at initial diagnosis

For example, if a specific primary tumor site had patients in only one database, none of these patients were used in the analysis. To match the age at initial diagnosis, the range (i.e., from the minimum to the maximum age) was computed from each database. Patients whose age at initial diagnosis fell into the overlap of the two ranges from the CTCA and SEER samples were included in the survival analysis.

4. Statistical analyses

The survival outcome from the CTCA database was defined as the time from the initial diagnosis to death and computed in number of years as the difference between the date of death and the date of initial diagnosis divided by 365.25. The survival outcome from the SEER database was provided by the SEER Limited-Use Data File as the number of completed years and the number of completed months. These were then converted to the number of years by dividing the number of total months by 12. For these patients who were still alive or lost to follow-up at the time of entering the databases, their survival time was treated as statistically censored [1] at the difference between the date of last contact and the date of initial diagnosis.

For each survival outcome from each database, the survival curve, defined as the probability of cancer patient survival as a function of time after the initial diagnosis, was estimated by the nonparametric product-limit method [1]. Formal statistical analysis of the esophageal cancer survival distributions between the CTCA database and the SEER database were conducted by the nonparametric logrank test and Wilcoxon test as well as the likelihood ratio test [1].

Point estimates and 95% confidence interval estimates were used to estimate the survival rate of esophageal cancer patients 0.5 years, 1 year, 1.5 years, 2 years, 2.5 years, 3 years, 3.5 years, 4 years, 4.5 years, and 5 years after the initial diagnosis. Similar estimates were also computed to estimate the difference of the survival rates at these time points between the two cohorts. Because the estimated survival curves might not estimate the survival probability at these specific time points, survival rates from the closest observed survival times were used. Because five-year survival rates have been popularly used in many cancer survival reports, five-year survival curves were also obtained by treating those who survived more than five years after the initial diagnosis as statistically censored at five years. Because patients surviving more than five years remained part of the risk sets in the estimation of survival rates at any time within five years of diagnosis, the truncated survival curves were identical to the first portion of the complete survival curves. These analyses were implemented by SAS/PROC LIFETEST [2] and SAS macros.

Covariates such as age at initial diagnosis, gender and year of initial diagnosis could affect the survival of esophageal cancer patients. Therefore, additional adjusted analyses were completed on the survival outcomes between the CTCA and SEER samples after adjusting for the effects of these covariates. More specifically, the effect of each of the covariates (age at diagnosis (young vs. old through the median split), gender and year of initial diagnosis (2000 to 2004 vs. 2005 to 2009)) was adjusted in the survival analysis of the CTCA and SEER samples through a stratified logrank test and Wilcoxon test as well as through a stratified Cox proportional hazards model treating each covariate as a stratum [1], the latter of which was implemented by SAS/PROC PHREG [2]. Another Cox proportional hazards model was also used to simultaneously adjust for the effects of all three covariates (age at diagnosis, gender and year of initial diagnosis) in the survival analysis.

Estimated Five-Year Survival Curves
Metastatic Esophageal Cancer Patients Diagnosed from 2000 to 2009
CTCA and SEER Samples

esophageal estimated survival curve

Limitations of the Analysis

This analysis has limitations. First, this is a retrospective, observational study, not a prospective, randomized trial. Although a large cancer sample was available from the SEER Program across many geographic regions in the United States, both samples, especially the sample from CTCA, are convenience samples. The nature of the observational study on the convenience samples prevents a causal interpretation of the statistical inferences, i.e. a cause and effect relationship cannot be established.

Second, although some types of matching, as described above, were implemented to select the appropriate SEER and CTCA patient samples, the distributions of important covariates such as age at initial diagnosis, gender, and year of initial diagnosis were not identical between the CTCA sample and SEER sample; even with the adjusted analysis, the possible confounding by these factors of the analyses and results cannot be ruled out. Further, many factors (e.g., income, access to health care, mobility) other than those considered in the analysis, and available from the databases, could also have contributed to the survival outcomes. The possible confounding by these factors of the analyses and results cannot be ruled out.

Third, the survival analysis was based on the statistical analysis of the rate of death from all possible causes, not solely the cancer-specific death. Data are not available for a statistical analysis of cancer cause-specific death rates.

Fourth, across the 11 cancer types for which survival results are presented on the CTCA website, 0.48% of all the CTCA analytic cancer cases eligible for and included in the analyses were diagnosed by CTCA, but received no initial course of treatment at CTCA. A similar statistic for each individual type of cancer included in the analysis is not currently available. Also, there is a possibility that the SEER database may contain some of the CTCA cancer cases, and the latest SEER Limited-Use Database (as of 2012) does not allow the identification and exclusion of such patients from the analysis.

Finally, although a large cancer sample was available from the SEER database, the sample size from CTCA was limited. A larger CTCA sample size would be needed to provide a more definitive survival analysis.

References

[1] Kalbfleisch JD, Prentice RL. The Statistical Analysis of Failure Time Data. New York: John Wiley, 1980.
[2] SAS Institute Inc., SAS/STAT User’s Guide, Volume 2, Version 6, 1990. Cary, NC, USA.

* The SEER data represent national results over a large number of institutions and have been included for illustrative purposes. They are not intended to represent a controlled study and/or a perfect analysis of the CTCA and SEER data because of variability in the sample sizes of the two data bases, the clinical condition(s) of the patients treated, and other factors.

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