The Response Evaluation Criteria in Solid Tumors (RECIST), based on differences in tumor size, has been considered as a reproducible method that facilitates not only the measurement of the mass but the evaluation of response to given treatments; while classic chemotherapy induces a reduction of the tumor, new target therapies frequently produce the stabilization of the disease or a delayed progression. These new therapeutic alternatives have shade light on the limitations of the RECIST criteria, since the response to these type of treatments are basically associated with changes on the radiological characteristics of the tumor, as well as other findings in functional imaging.

This study is aimed to compare the response rates according both Choi and RECIST criteria.

Inclusion Criteria:

• Patients with a pancreatic neuroendocrine tumor with a Ki67 index <20%, who accept to participate and sign the consent form. In case of death patients, waiver of consent has been considered.
• Patients who, according daily clinical practice, have been treated with sunitinib between February 2012 to end of inclusion period, with a follow up of at least 6 months.
• Patients with a baseline imaging study (TC with arterial phase) and, at least, a 6-months follow-up evaluation. Patients with progression or exitus before the first imaging evaluation will not be included.

Exclusion Criteria:

• Patients with a follow-up of <6months because of any other cause beyond progression of disease or exitus.
• Patients without a baseline radiological evaluation or at 3/6 months.
• Patients who do not accept to participate in the study.
• Patients with anti-angiogenic treatment within 3 months prior to the start of sunitinib treatment.
• Patients treated with sunitinib plus any other anti-proliferative agent beyond ASS.

Patients with a neuroendocrine pancreatic tumor, treated with sunitinib, with at least one radiological evaluation every 6 months.