It's possible. I've seen 3 in cars from a long ago job at a used car lot. They were a '72 240D, '83 300D, and an '84 300SD. In all cases the chain itself broke. The 240D broke the cam and cracked the #2 piston. The 300SD bent some valves and cracked the cam towers. The 300D was very lucky, no damage other than the chain.

I feel the chain and rails should be a scheduled preventive maintenance item to be changed at 8* stretch (At the camshaft) or 250K miles. It's around $250 for parts for $250K miles. Compare that to a possible $800-2500+ in repairs or a rebuild.