Clinical Investigations
A population-based study of rectal cancer: permanent colostomy as an outcome

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Abstract

Purpose: The objectives of this study are to describe the utilization of surgery and of radiotherapy in the treatment of newly diagnosed rectal cancer in Ontario between 1982 and 1994, and to describe the probability of permanent colostomy at any time after the diagnosis of rectal cancer, as an outcome of the treatment of newly diagnosed rectal cancer.

Methods and Materials: Electronic records of rectal cancer (International Classification of Diseases code 154) from the Ontario Cancer Registry (n = 18,695, excluding squamous, basaloid, cloacogenic, and carcinoid histology) were linked to surgical records from all Ontario hospitals, and radiotherapy (RT) records from Ontario cancer centers. Procedures occurring within 4 months of diagnosis, or within 4 months of another procedure for rectal cancer, were considered part of initial treatment. Multivariate analyses controlled for age, sex, and year of diagnosis.

Results: Resection plus permanent colostomy was performed in 33.1% of cases, whereas local excision or resection without permanent colostomy was performed in 38.2%. Multivariate logistic regression demonstrated higher odds ratios (OR) for resection plus permanent colostomy in all regions of Ontario relative to Toronto. The OR for postoperative RT following local excision or resection without permanent colostomy varied among the regions relative to Toronto (e.g., OR Ottawa = 0.59, OR Hamilton = 0.76, OR London = 1.25). The relative risk (RR) of colostomy conditional upon survival within 5 years from diagnosis varied among regions relative to Toronto (e.g., RR Ottawa = 1.21, RR Hamilton = 1.20).

Conclusions: There is regional variation in the utilization of resection with permanent colostomy, and in the utilization of postoperative RT among cases not undergoing permanent colostomy. Regions with higher initial rates of resection plus permanent colostomy continue to experience higher probability of permanent colostomy 5 years after diagnosis of rectal cancer. Higher initial rates of permanent colostomy may be malleable to interventions aimed at improving overall outcomes.

Introduction

The main component of the curative treatment of rectal cancer is surgery. Evolution of the surgical treatment of newly diagnosed rectal cancer has been directed at improving quality of life by reducing the indications for permanent colostomy. More frequent use of low anterior resection has been recommended compared to abdominoperineal resections, and sphincter-sparing local excisions have also been recommended for selected cases 1, 2. Other therapies for rectal cancer include the use of radiotherapy (RT) and/or chemotherapy as adjuvants to surgery, or as therapies when curative surgery is not appropriate.

Randomized clinical trials have shown survival benefit from combined adjuvant chemotherapy plus postoperative RT (3). The benefit of chemotherapy combined with postoperative RT was highlighted at a consensus conference in 1990, and in a Clinical Announcement by the National Cancer Institute (Bethesda, Maryland, USA) on March 14, 1991 (4). The benefit of adjuvant chemotherapy plus postoperative RT is thought to relate to the eradication of micrometastatic disseminated disease by chemotherapy and the eradication of microscopic residual disease in pelvis/rectum by the combined effect of chemotherapy plus RT.

The magnitude of benefit from therapies for which efficacy has been demonstrated in randomized clinical trials may be lower than expected, when these therapies are adopted in practice 5, 6. Reasons for this may include greater heterogeneity among patients, physicians, institutions, and treatment processes in practice, compared to these factors in randomized clinical trials. Description of the outcome of surgery and RT for newly diagnosed rectal cancer is a method of assessing the effectiveness, in the real world, of procedures proven to be efficacious in the controlled experimental setting of clinical trials 5, 7, 8.

We have performed a population-based study to describe the use of surgery and RT for newly diagnosed rectal cancer, and the subsequent risk of permanent colostomy. The study will illustrate the extent to which initial treatment procedures avoiding permanent colostomy are associated with being free of permanent colostomy during the 5 years after diagnosis and treatment. It also provides the opportunity to examine the relationship between potentially malleable variations in practice and outcome. Practice guidelines, feedback from audits, and educational programs may be required to improve outcomes.

Section snippets

Methods

We performed a population-based cohort study of the utilization and outcome of surgery and RT for rectal cancer, newly diagnosed in Ontario between 1982 and 1994. Cases of rectal cancer were identified from the Ontario Cancer Registry (OCR), under the International Classification of Diseases (ICD) code 154. We excluded cases with codes 154.2 and 154.3 (anal cancer), as well as cases under ICD 154.0, 154.1, and 154.8 with the morphology codes for squamous, cloacogenic, carcinoid, adnexal and

Results

The study population was composed of 18,695 cases after excluding 1344 cases because of anal cancer subsites (ICD 154.2, 154.3), or ICD-O histology codes that were inconsistent with adenocarcinoma of the rectum.

Discussion

We have observed changes in the rates of utilization of surgery and postoperative RT following the diagnosis of rectal cancer over time, in a direction that is consistent with recommended trends in the medical literature, and with the adoption of the results of clinical trials and consensus panels. Similar findings have been observed in a population-based study in France, in which Goudet et al. (12) demonstrated increasing rates of resection in an unselected population over time between 1976

Conclusion

This study has used population-based electronic data sources to illustrate the effectiveness of resection or local excision without permanent colostomy in the treatment of newly diagnosed rectal cancer. By this approach, we have observed regional practice variations that have parallels in regional outcome variations. These parallels present potential opportunities to improve patient outcomes by interventions to change practice patterns. These interventions may include practice guidelines,

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The Radiation Oncology Research Unit is supported by a grant from Cancer Care Ontario.

1

Dr. Paszat and Dr. Groome are Career Scientists of the Ministry of Health of Ontario.

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