In my dad's case, the tumor just grew in 6 months (first diagnosis). He had the lung x-ray in Sept 2002 and the result was very good that nothing was found and very clear. Ironically, he was diagnosed in March of 2003. Cancer is a thing that it can grow in a very incredibly fast pace, especially SCLC, my dad's brain tumor was cut off, but in 1 1/2 month, the brain tumor recurred again. Neurosurgeon leader told us, it was rare that he never see this case which the tumor can grow in such a fast pace.
I think it's like a explosion, once it happens, you can stop it.