Physicians in Medford, Mass.-based  seek to end their two-decades-long affiliation with Partners HealthCare

The about 400 physicians  now part of the Hallmark Health System, based in Medford, Mass., just north of Boston, have decided to join the New England Quality Care Alliance, a rival network affiliated with Tufts Medical Center, in Boston.The Tufts network now has about 1,800 physicians.

Since physicians tend to refer patients  to specialists and hospitals within their own networks, the plan could result in more referrals to Tufts, and fewer to Partners hospitals, particularly prestigious Massachusetts General and Brigham and Women’s. Partners has faced much scrutiny in recent years from regulators for what some have seen as its excessive pricing power in metropolitan Boston.