This non-interventional retrospective medical record review study will assess the prevalence of KRAS testing and the impact of the KRAS test result on patterns of Vectibix use in patients with metastatic colorectal cancer (mCRC) treated with Vectibix in selected European countries over 3 rounds. As the optimal use of Vectibix also requires accurate KRAS mutation testing, this study will also assess data from the laboratory that performed the KRAS test. The study will also monitor changes in the pattern of Vectibix treatment between the different rounds of the study.

The medical record review will be conducted for 3 rounds in months 0, 12, and 24 after the first medical record abstraction. Before the beginning of the study, a sampling list will be created by Amgen by merging lists of oncologists (and their contact information) to be collected from Cegedim, the ESMO, from major cancer centers and oncology clinics in various countries within Europe. In each round of medical record review, potential participating oncologists will be randomly sampled from all identified oncologists. Potential oncologists will be contacted by letter, telephone or email. The oncologists will be introduced to the study, and their eligibility to participate in the study will be assessed using a standardized questionnaire. The number of oncologists sampled per country will be proportional to the number of oncology centers per country. Approximately 50 oncologists will participate in each round of the study. From each eligible participating oncologist, study staff will then obtain approximately 3 or more medical records for patients who have received Vectibix for the treatment of mCRC during the 6-month period prior to the time of contact with the relevant oncologist and are not involved in an experimental clinical trial when treated with Vectibix. A written consent may be obtained from participating patients to access their medical records, depending on local laws. Medical information will be abstracted from the medical records using standardized forms. Such medical information will include the occurrence and timing of treatment with Vectibix and oxaliplatin-containing chemotherapy, diagnosis of mCRC and the occurrence, timing and results of KRAS testing. The oncologist will also be asked to collect information from the pathology laboratory that performed the KRAS mutation test on the patient, using a standardized pathology data extraction form.

Physician Inclusion Criteria:

• Must be a practicing oncology specialist
• Must treat at least 5 new or continuing patients with metastatic colorectal cancer per quarter
• Must have prescribed Vectibix to treat at least 5 new or continuing patients with metastatic colorectal cancer in the past 6 months

Physician Exclusion Criteria:

• Must be the only oncologist sampled at the same medical centre for that round of the study
• Must not have taken part in the study previously

Patient Inclusion Criteria

• Must have received Vectibix for the treatment of metastatic colorectal cancer during the 6-month period prior to the time when medical records are obtained
• Must not have been in any experimental clinical trial at the time of receiving Vectibix
• Must provide written consent to allow access to their medical records (if local laws require it)
• Must not have taken part in the study before

Oncologists satisfying all of the physician eligibility criteria will be eligible to participate in the medical records review study. From each eligible oncologist, medical records from 3 or more patients who satisfy all the patient inclusion criteria will be obtained.