There are only a few cancers which can be cured eventhough they have spread everywhere. One of these are testicular germ cell tumours (eg Lance Armstrong), as well as some rare types of gestational trophoblastic disease (essentially out of control placenta) and acute leukaemia and lymphoma. It's not big news because these tumours are quite rare, and treatment for leukaemia/lymphoma has always worked better than for solid tumours. There is also nothing to be gained from a public health persepctive by telling people that testicular cancer can be cured with multiple cycles of chemo, surgery and radiotherapy.

Some cases of advanced colon cancer can be cured if the disease has only spread to the liver, by cutting out the disease in the liver.

But your most common cancers eg breast, lung, colon for the most part, gastric,prostate... they aren't curable once widespread.