Der Arzt von Stalingrad (The Doctor of Stalingrad) was one of four films directed in 1958 by the prolific Hungarian-born helmsman Geza von Radvanyi.   Set in a Russia POW camp after the end of the Second World War, the film concentrates on an imprisoned German doctor, played by O.E. Hasse.   Denied sophisticated surgical tools, the doctor relies solely upon his medical skill to pull his patients through.   He manages to win the confidence and respect of his Soviet captors when he removes a brain tumor from the son of the commandant.   Less happy are the results of a wartime romance between his assistant and a female Russian physician.  Though not altogether sympathetic to the Russians, neither can Der Arzt Von Stalingrad be considered entirely pro-German.