AMSTERDAM — The frequency of doctor-assisted euthanasia in the Netherlands has changed little since the longstanding practice was legalized in 2002, according to a study Wednesday.

A summary published on The Lancet magazine’s website said that ‘‘in 2010, of all deaths in the Netherlands, 2.8 percent were the result of euthanasia. This is higher than the 1.7 percent in 2005, but comparable with [levels seen] in 2001 and 1995.’’

Under Dutch law, a person who asks to die may be administered a lethal mixture of sedatives and muscle relaxants if two doctors agree he or she is suffering unbearable pain with no prospect for recovery.

Most cases involve cancer.

The study in the Lancet used data from the country’s death registry and sent confidential questionnaires to doctors, extrapolating results to represent a cross-section of deaths in different social, medical and geographical areas.

Dutch doctors are also required to report all euthanasia cases on a nonconfidential basis to the country’s Euthanasia Commission, but this method is widely believed to underreport the total number of euthanasia cases.