MIAMI - A federal judge approved an agreement Monday under which health insurer Cigna will pay $540 million to settle claims that it systematically underpaid the nation's 950,000 doctors.

Cigna followed the lead of Aetna in settling racketeering lawsuits against managed care industry leaders. Both companies are paying refunds to doctors and have changed procedures for reviewing and processing doctors' claims for payment.

Cigna's settlement, coming on top of Aetna's $470 million agreement in May, may pressure eight other insurers sued by the doctors to settle. They are Anthem, Coventry, Foundation, Humana, PacifiCare, Prudential, United and Wellpoint.

Philadelphia-based Cigna agreed to spend $400 million on internal changes, and to pay at least $70 million to doctors on claims up to 12 years old, $55 million in attorneys' fees and $15 million to create a health care foundation.

The doctors' primary complaint is that the companies' computers routinely "downcoded" their claims by treating services or procedures as less intensive, thereby paying less. Cigna agreed to stop such automatic processing.

Under the settlement, questions of medical necessity for services will be decided by doctors, a hot-button issue for doctors and patients. Cigna and the doctors also agreed to jointly decide how to handle experimental and investigational treatments.

Dr. W. Allen Schaffer, Cigna's chief medical officer, called the agreement "a prescription for a stronger, more collaborative working relationship between doctors and Cigna."