Background: Patients with high-risk stage III colon cancer have a significantly poorer prognosis than those with stage II or low-risk stage III colon cancer. Despite this distinction, most guidelines recommend similar adjuvant treatment approaches for all stages, and there is a dearth of research focusing on high-risk stage III colon cancer and the potential for improved prognosis through more intensive adjuvant treatment. Given the proven efficacy of triplet chemotherapy in metastatic colorectal cancer, this study aims to assess the effectiveness and toxicity of modified 5-fluoropyrimidine (5-FU)/leucovorin plus irinotecan and oxaliplatin (mFOLFIRINOX) in comparison with the current standard of care—modified oxaliplatin and 5-FU (mFOLFOX-6)—as an adjuvant treatment for patients diagnosed with high-risk stage III colon cancer. Methods: This multicenter, randomized (1:1), open-label, phase II trial aims to compare the adjuvant treatment efficacy of mFOLFIRINOX and mFOLFOX-6 in patients with high-risk stage III colon cancer. The trial aimed to enroll 312 eligible patients aged between 20 and 70 years with an Eastern Cooperative Oncology Group performance status of 0-2, or between 70 and 75 years with an Eastern Cooperative Oncology Group performance status of 0. All patients underwent radical resection and were randomized into two arms: Arm A experimental arm, received 12 cycles of mFOLFIRINOX every 2 weeks, while arm B, the reference arm, received 12 cycles of mFOLFOX 6 every 2 weeks. The primary endpoint of this study was the 3-year disease-free survival, whereas the secondary endpoints included assessing the 3-year overall survival and treatment toxicity. Discussion: The Frost trial is expected to elucidate the safety and oncologic efficacy of mFOLFIRINOX compared to mFOLFOX 6 as adjuvant treatment for high-risk stage III colon cancers, and provide evidence about this treatment, and contribute to improve the prognoses ultimately. Clinical trial information: NCT05179889.