BACKGROUND: Clinical guidelines recommend altering chemotherapy treatment by decreasing, delaying, or discontinuing dosing in patients who are experiencing chemotherapy-induced peripheral neuropathy. There are few data available on the clinical use of treatment alteration including the severity of CIPN at the time of treatment alteration. METHODS: This was a retrospective analysis of patients receiving oxaliplatin on the NCCTG N08CB trial. Neuropathy severity was assessed at each cycle by clinicians and patients. Patients were classified as (1) completed treatment without alteration, (2) dose reduction or delay due to neuropathy, (3) discontinuation due to neuropathy, (4) discontinuation for other toxicity, or (5) discontinuation for another reason (5). Comparisons focused primarily on patients with alteration due to neuropathy (groups 2 and/or 3) compared with patients who completed treatment without alteration (group 1). RESULTS: In 350 participants, 135 (39%) completed treatment without alteration, 70 (20%) had a dose reduction or delay due to neuropathy, and 35 (10%) discontinued early due to neuropathy. Clinician-assessed neuropathy severity was greater in patients at the time of dose reduction or delay compared with severity at the end of treatment in patients without alteration (p < 0.0001). Patient-reported neuropathy severity at cycle 4 was worse in patients who eventually had a reduction or delay as compared with patients who completed treatment without alteration (p = 0.017). CONCLUSIONS: Treatment alterations due to neuropathy are common in patients receiving oxaliplatin for colon cancer and are associated with clinician-assessed neuropathy severity. Rapid increases in patient-reported neuropathy severity indicate a potential need for monitoring and intervention. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT01099449 (NCCTG N08CB).