New Colon Cancer Staging System Improves Survival Forecasts

TOPLINE:

The new Sassun-Mayo staging system, which integrates tumor deposit and lymph node counts, improves prognostic accuracy for patients with colon cancer compared to the standard American Joint Committee on Cancer (AJCC) staging system. An analysis of institutional and national cohorts found that the new system provided better overall survival predictions and staging for patients with stage III colon cancer.

METHODOLOGY:

• Tumor deposits negatively impact colon cancer survival, but the AJCC tumor, lymph node, and metastasis (TNM) staging system only considers these deposits in the absence of positive lymph nodes. This approach may lead to understaging and suboptimal prognostic accuracy.
• Researchers developed and validated the Sassun-Mayo staging system for colon cancer, which combines tumor deposit and positive lymph node counts while maintaining the AJCC staging framework.
• The researchers assessed data on 788 patients with colon cancer (mean age, 58.5 years) from an institutional database and 77,790 patients from the National Cancer Database (mean age, 59.3 years).
• A real positive lymph node count was used to derive Sassun-Mayo N/TNM stages, which were compared with AJCC N/TNM stages. The researchers compared the two staging systems in their ability to predict time to death and overall survival at 3 years.

TAKEAWAY:

• In the institutional cohort, the area under the curve (AUC) for predicting 3-year death was higher for the Sassun-Mayo N stage relative to the AJCC N stage (AUC, 0.64 vs 0.62; P = .33). Similar improvements were observed for Sassun-Mayo TNM staging (AUC, 0.66 vs 0.63; P = .19), but neither comparison reached statistical significance. Findings were similar in the national cohort, but the both comparisons reached statistical significance.
• Using the Sassun-Mayo system, 11.9% of patients in the institutional cohort were upstaged from N1 to N2 and 4.4% were upstaged from N2a to N2b. This upstaging led to improved stratification of survival outcomes, with Kaplan-Meier curves indicating a 5.1% difference in 3-year overall survival for patients upstaged from N1 to N2 using the Sassun-Mayo system and a 21.2% difference for those upstaged from N2a to N2b.
• Applying the Sassun-Mayo system to the national cohort, 13.2% of patients were upstaged from N1 to N2. Upstaged patients had an almost identical 3-year overall survival rate compared to AJCC N2a patients without tumor deposits. Additionally, 3.9% of patients were upstaged from N2a to N2b using the Sassun-Mayo system, revealing a 3-year overall survival similar to that of AJCC N2b patients without tumor deposits. Taken together, the findings indicate that 17.1% of patients with stage III colon cancer were initially understaged using the AJCC system.

IN PRACTICE:

Implementation of Sassun-Mayo N and TNM staging would “improve the prognostication of colon cancer,” the study authors concluded.

“Excluding tumor deposits from the staging system may lead to understaging of patients, which may impact the treatment that they receive,” experts wrote in an invited commentary. “This is especially important because significant clinical decision-making, particularly regarding chemotherapy for stage III colon cancer, is currently guided by tumor stage.”

SOURCE:

The study, led by Richard Sassun, MD, Division of Colon and Rectal Surgery, Mayo Clinic, Rochester, Minnesota, was published online in JAMA Surgery, alongside an invited commentary.

LIMITATIONS:

The retrospective nature of the study could have introduced bias. The duration and regimens of chemotherapy were not specified. Missing data across variables for both cohorts were present but were excluded from survival analyses. The National Cancer Database did not disclose cancer status, which prevented validation of disease-free survival. Additionally, the staging system was not validated for rectal cancer due to potential confounders from varying neoadjuvant treatment modalities.

DISCLOSURES:

The authors did not declare any funding information. One author reported holding a patent for blood-based inflammatory biomarkers for predicting surgical outcomes, with royalties paid. No other disclosures were reported.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.