More doctors smoke Camels than other brand. 补充完整为：

1. More doctors smoke Camels than smoke any other brand.

2. More doctors smoke Camels than do any other brand.

【说明】原句other brand 有误，漏掉了any，应改为any other brand。因为brand 是可数名词单数，不能没有冠词或any 限定词。其可能的表达方式应位：

another brand

the other brand

any other brand

some other brand

但不可说：other brand

本句的“比较对应项”是more doctors，在than 从句中必须省却，或者假想由than 充当。