Adherence to Treatment Guidelines Varies Widely in Colon Cancer



SAN ANTONIO – Young, healthy patients with early-stage colon cancer are more likely to be overtreated, whereas older, uninsured patients with higher-risk disease tend to be undertreated, according to an analysis of 236,964 cases.

"Although adherence [to stage-specific treatment guidelines] has increased over the past 5 years, significant variability still exists," Dr. Ryaz B. Chagpar said during a plenary session at a symposium sponsored by the Society of Surgical Oncology.

Dr. Ryaz B. Chagpar

Treatment guideline adherence has been proposed as a potential measure of the quality of cancer care. Colon cancer guideline adherence is a potentially attractive quality measure since consensus on treatment standards exists among several agencies including the National Comprehensive Cancer Network (NCCN), the American Society for Clinical Oncology, and the National Quality Forum, he said. However, nationwide assessment of current stage-specific colon cancer treatment practices is lacking.

Using the National Cancer Data Base, Dr. Chagpar and his colleagues in the department of surgical oncology at MD Anderson Cancer Center in Houston, identified all patients diagnosed with colon cancer from 2003 to 2007. The database captures about 70% of all annual cancer diagnoses within the United States from more than 1,430 hospitals, and is a joint program of the American College of Surgeons Commission on Cancer and the American Cancer Society.

After excluding hospitals that were only diagnostic, the researchers identified 236,964 patients. The patients were then restaged from pathological variables according to the American Joint Committee on Cancer 6th edition staging manual, and grouped according to whether their treatment was adherent with NCCN guidelines. Of note, stage II disease was stratified into low- and high-risk disease based on the guidelines, with the latter defined as patients with T4 lesions, those with less than a 12-node lymphadenectomy, and tumors categorized as at least grade 3 or resected with positive margins.

Adherence for stage I and low-risk stage II colon cancer was defined as surgical resection. Nonadherence included the recommendation of adjuvant chemotherapy, independent of whether the treatment was actually received (overtreatment), or no adequate surgical resection (undertreatment), Dr. Chagpar said.

For stage II high-risk disease, adherence was defined as the consideration of adjuvant chemotherapy following surgical resection. Overtreatment included the addition of radiation to chemotherapy and undertreatment was surgical resection alone.

Adherence for stage III disease was defined as that for stage II high-risk disease. The only difference for stage IV adherence was the recommendation of chemotherapy, independent of whether surgical resection was performed, he explained.

Patients with stage I colon cancer were significantly more likely to receive guideline-based treatment, at 95.5%, compared with 74% for low-risk stage II, just 27% for high-risk stage II, 64.5% for stage III, and 68% for stage IV (P value less than .0005).

The researchers then performed hierarchical regression modeling that controlled for heterogeneity at both the hospital level and patient level to determine factors associated with adherence.

Interestingly, for stage I and low-risk stage II disease, increasing age as well as increasing Charlson-Deyo Comorbidity Index was associated with a greater likelihood of receiving adherent treatment, whereas for higher-risk disease, older patients as well as those with a greater number of comorbidities were less likely to receive guideline-based treatment, Dr. Chagpar said.

Also, a later year of diagnosis (2007 vs. 2003) was associated with greater likelihood of receiving guideline-based treatment regardless of disease stage. The same was true for having private insurance, with the exception of low-risk stage II disease.

Nonadherence for stage I and low-risk patients was largely attributable to overtreatment in the form of recommendations for adjuvant chemotherapy, particularly in young, healthy patients and those with private insurance, Dr. Chagpar said.

Nonadherence for high-risk stage II, stage III, and stage IV disease was primarily due to undertreatment, particularly for older, uninsured patients and those with a number of preexisting comorbidities.

"Given that guideline-based care, however, does not necessarily translate into improved survival and patient-reported outcomes, the impact of nonadherence on the quality of cancer care needs to be further elucidated," he concluded.

Limitations of the study include variability in the level of evidence used to construct NCCN guidelines; a lack of pathological staging data for 15% of patients; and a lack of data on some factors used to characterize high-risk stage II disease, such as lymphatic vascular invasion and obstruction. In addition, systemic therapy is often underreported in cancer registries, the authors said.

The authors reported no conflicts of interest.

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