Many patients with colon cancer, including almost 75% of patients with high-risk stage II disease, are not treated in accordance with National Comprehensive Cancer Network (NCCN) guidelines, according to a study presented at the 2011 annual meeting of the Society of Surgical Oncology.

Using data from the National Cancer Data Base, researchers identified 236,964 patients diagnosed with colon adenocarcinoma between 2003 and 2007. The patients were restaged based on pathologic variables according to the American Joint Committee on Cancer sixth edition and assessed for adherence with stage-specific NCCN guidelines.

Analysis revealed that 73.1% of high-risk stage II patients were not recommended for adjuvant chemotherapy. Stage II patients were, by far, the least likely to receive guideline-adherent treatment.

For all other stages of patients, the majority was treated according to NCCN guidelines. Adherence rates varied, ranging from 95.5% for stage I, 74.1% for low-risk stage II, 64.5% for stage III and 68.3% for stage IV.

Adherence to NCCN guidelines has improved over the past five years, but many patients still experience undertreatment or overtreatment by NCCN standards, said co-author Ryaz Chagpar, MD, clinical research fellow at the University of Texas MD Anderson Cancer Center in Houston. “Considerable variability still exists in the treatment of colon cancer across the nation, especially for patients with high-stage stage II and stage III disease,” he said.

Patients with stage I and low-risk stage II disease are more likely to be overtreated, particularly young healthy patients, whereas nonadherence for high-risk stage II, stage III and stage IV disease is primarily due to undertreatment of older, uninsured patients and those with preexisting comorbidities, according to the study.

These variations in treatment can have significant effects on the health care system, said Clifford Ko, MD, director of the UCLA Center for Surgical Outcomes and Quality, in Los Angeles.

“The clinical implications of the study are meaningful because as a health care system, it is the goal to minimize or prevent overutilization and underutilization as we strive to achieve optimal care," said Dr. Ko.

Lack of recommendations was largely responsible for nonadherence in patients with high-risk stage II (91.9%) and stage III (82.1%) disease, results showed.

That’s not surprising, as the survival benefit of adjuvant chemotherapy in stage II colon cancer is highly controversial, said Dr. Chagpar.

Randomized trials, meta-analyses and pooled analyses have come to mixed conclusions over the question of adjuvant chemotherapy in these patients.

Both the American Society for Clinical Oncology and the NCCN recommend against the routine use of chemotherapy for stage II patients. At the same time, both organizations advocate “the consideration of adjuvant system therapy” for a subset of patients with high-risk features such as T4 lesions, high-grade tumors, lymphovascular invasion, frank perforation, positive resection margins or those who have received a lymphadenectomy of fewer than 12 nodes.

“Given this controversy, it is perhaps not surprising that even within this subset of high-risk stage II patients, the recommendation of adjuvant chemotherapy is quite variable across the nation,” said Dr. Chagpar.

When investigators looked at factors affecting adherence, they found age, race, Charlson-Deyo Comorbidity Index, later year of diagnosis and insurance status were significant, using stage-specific models.

Guidelines are garnering more attention in recent years as a potential measure for quality of care. That attention is likely to increase with the Patient Protection and Affordable Care Act’s Value-based Purchasing Program, which will provide financial incentives to providers and health systems to improve quality, coordinate care and cut costs.

But whether guidelines can be used as a surrogate for quality of care is still up for debate, said Dr. Chagpar.

The study had several limitations, including a lack of pathologic staging data for all patients, variability in the level of evidence used to construct the NCCN guidelines and the potential for underreporting of systemic therapy.