SUMMARY: ColoRectal Cancer (CRC) is the third most common cancer diagnosed in both men and women in the United States. The American Cancer Society estimates that approximately 152,810 new cases of CRC were diagnosed in the United States in 2024 and about 53,010 patients died of the disease. The lifetime risk of developing CRC is about 1 in 23.
Colon cancer treatment strategies have advanced significantly over the years. Since 2004, the introduction of Oxaliplatin into adjuvant chemotherapy regimens has been a cornerstone in improving outcomes for patients with Stage III colon cancer. The most commonly adopted protocols include FOLFOX (a combination of Folinic acid or Leucovorin, 5-fluorouracil (5-FU), and Oxaliplatin) and a regimen combining Capecitabine with Oxaliplatin. These regimens gained validation through critical trials such as MOSAIC, NSABP C-07, and XELOXA, which demonstrated the survival benefits of Oxaliplatin-based combinations.
However, for patients with Stage II colon cancer, the role of adjuvant chemotherapy remains controversial. While many oncologists recommend adjuvant therapy for Stage II patients, its effectiveness is not universally supported by clinical data. The QUASAR trial showed limited benefits of Leucovorin and 5-FU in this population. Adding Oxaliplatin to adjuvant regimens has been explored to improve outcomes, particularly for high-risk patients. However, Oxaliplatin can be associated with neuropathy which can be long lasting or permanent, depending on the duration of therapy. Additional toxicities with longer duration of chemotherapy include diarrhea, fatigue as well as more office visits.
High-risk Stage II colon cancer is a heterogeneous group, and definitions of high-risk features vary across studies. High-risk features have included T4 tumors, bowel perforation, obstruction, poor histological differentiation, vascular invasion, or fewer than 10 lymph nodes examined. The heterogeneity of high-risk Stage II colon cancer complicates treatment decisions, with new clinical prognostic factors such as the site of tumor origin in the colon (tumor sidedness), age, and BMI having been described, in addition to the stage of the disease.
To clarify the benefits of Oxaliplatin in Stage II colon cancer, researchers performed a pooled analysis of the MOSAIC and NSABP C-07 trials. These studies collectively included 4,654 patients, of whom 1,595 had Stage II colon cancer, and were treated with either 5-FU and Leucovorin alone or 5-FU and Leucovorin plus Oxaliplatin. The Primary objective was to determine whether the addition of Oxaliplatin to 5-FU and Leucovorin provided a significant survival advantage for Stage II patients, particularly those with high-risk features. The analysis examined outcomes such as Overall Survival (OS) and Time to Relapse (TTR). Prognostic variables included T stage, presence of bowel perforation or obstruction, lymph node count, tumor sidedness, sex, age, and histological differentiation. Multivariable models and Kaplan-Meier survival analyses were employed to assess the impact of these variables. Patients with Stage III colon cancer were included only for interaction tests to compare treatment effects across stages.
The data from this pooled analysis revealed several important findings.
1. Prognostic Factors: Independent prognostic variables for Stage II colon cancer included sex, age, bowel perforation/obstruction, and tumor sidedness. These factors were associated with OS but did not predict a benefit from Oxaliplatin-based treatment.
2. Survival Outcomes: The addition of Oxaliplatin to 5-FU and Leucovorin did not significantly improve OS or TTR in Stage II colon cancer, even among high-risk subgroups. In contrast, a clear benefit was observed in Stage III colon cancer patients, suggesting a differential effect of Oxaliplatin based on cancer stage.
3. High-Risk Subgroup Analysis: Among patients with high-risk features such as T4 tumors or inadequate lymph node sampling, there was no statistically significant OS or TTR benefit from addition of Oxaliplatin to 5-FU and Leucovorin.
4. Interaction Between Stage and Therapy: The analysis confirmed an interaction between cancer Stage (II versus III) and the benefit of Oxaliplatin. Stage II colon cancer patients derived no added advantage from Oxaliplatin, while Stage III patients experienced substantial improvements in survival outcomes.
These results challenge existing guidelines from the American Society of Clinical Oncology (ASCO) and the European Society for Medical Oncology (ESMO), which recommend Oxaliplatin-based regimens for high-risk Stage II colon cancer. The findings suggest that current definitions of high-risk features are insufficient to justify the use of Oxaliplatin in this population. Moreover, discrepancies between Disease-Free Survival (DFS) and OS in Stage II colon cancer indicate that DFS is not a reliable surrogate endpoint in this group. The lack of benefit from Oxaliplatin emphasizes the need for more precise prognostic tools to identify Stage II patients who might benefit from adjuvant therapy.
Several limitations affected the study. Key data on biomarkers, such as MicroSatellite Instability (MSI) and MisMatch Repair (MMR) status, were unavailable for nearly half the cohort, preventing their inclusion in prognostic analyses. Emerging tools like circulating tumor DNA (ctDNA), which show promise in identifying relapse risk, were also unavailable during the study period. Despite the lack of benefit observed with Oxaliplatin, novel prognostic approaches are needed to identify Stage II colon cancer patients at a high risk of relapse. Future clinical trials incorporating ctDNA-based stratification may refine treatment approaches and reduce unnecessary exposure to neurotoxic agents like Oxaliplatin.
In conclusion, for patients with Stage II colon cancer, the addition of Oxaliplatin to 5-FU based adjuvant therapy does not improve Overall Survival or Time To Relapse. Current clinical and pathologic criteria for high-risk classification fail to justify the routine use of Oxaliplatin, emphasizing the need for alternative risk stratification tools. These findings call for a reevaluation of treatment guidelines to ensure that therapeutic decisions are informed by robust, individualized risk assessments.
Assessment of the Addition of Oxaliplatin to Fluoropyrimidine-Based Adjuvant Chemotherapy in Patients with High-Risk Stage II Colon Cancer: An ACCENT Pooled Analysis. Chibaudel B, Raeisi M, Cohen R, et al. J Clin Oncology 2024;42:4187-4195
