Study Protocol

UCAS Japan is encouraging patients to join this study when they receive a diagnosis of an unruptured cerebral aneurysm equal to or larger than 3 mm. The study is being conducted with the agreement of the ethical committee of each participating hospital and patients are enrolled only after consenting to participate. Each patient chooses whether to join after she or he is sufficiently informed.
At the initial registration (when the lesion is found), the patient’s physical and neurological condition and diagnostic information from images are reported to the UCAS office. Follow-up data are collected 3 months, 1 year, and 3 years after registration. Any changes, including the patient’s physical or neurological condition or new imaging studies, are also reported to the office.
All information is registered and stored in the UMIN computer. UMIN is the University Hospital Medical Information Network, and its central office is located in the University of Tokyo Hospital. When a patient is treated for an aneurysm, the method of treatment and the outcome are reported.


UCAS Japan (Unruptured Cerebral Aneurysm Study of Japan)

Based on the findings from a preliminary survey in 1999, the Japan Neurosurgical Society started a clinical research project in January of 2001, aiming to prospectively collect data on as many unruptured cerebral aneurysms as possible. The primary purposes are to investigate the natural history of these lesions and the outcome of any treatment. The data are expected to contribute to the establishment of treatment guidelines for patients with unruptured cerebral aneurysms.

Organization of UCAS Japan

The goals of UCAS Japan

The goals of UCAS Japan are:
  1. To prove that the annual rupture rate of unruptured cerebral aneurysms with a diameter equal to or greater than 5 mm is higher than 0.5%
  2. To clarify the natural course of unruptured cerebral aneurysms and any associated risk factors
  3. To clarify the management risks of unruptured cerebral aneurysms

Treatment of unruptured cerebral aneurysms

This study does not restrict the selection of treatment. Each patient is sufficiently informed about the risks of leaving the aneurysm untreated or having treatment. Each patient then decides which approach to take.

Data management

All data are encrypted and transferred through the UMIN network and stored in the central computer in the University of Tokyo Hospital. Private information for each individual is restricted to the name (initials only), birth date, and registration number of each hospital. Since the data are scrambled with 128-bit encryption, the data transfer is as secure as possible.

Duration of data acquisition

Data are collected for 3 years after the registration of each case. The follow-up period may be extended, if necessary, but only when the patient agrees to the extension.

Numbers of patients

Every year, about 5,000 patients receive a diagnosis of unruptured cerebral aneurysm. We anticipate that most of these patients can join in this survey.

See details for Required Case Volume Assessment to reject the null hypothesis (annual rupture rate of unruptured aneurysms sized 5mm or larger is less than 0.005).

How the study is progressing

The enrollment of cases began January 1, 2001. As of January 15, 2004, 6,528 patients have been registered in the study, and 401 hospitals have participated.
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