I can answer a few of your questions and this is the right place to find some hope, as you will hear from folks that have continued to kick lung cancer's butt despite the initial diagnosis.
Palliative means that they are treating the cancer to alleviate the symptoms but not with the aim to cure it. However, not treating with curative intent is not hopeless. I once described this to a family member as - you can't 'beat' the cancer, but you can sure as heck beat it back down and hope to do that for as long as is possible. You will find people here that have been doing that for years.
As to why only 4-6 cycles of the chemo - this is standard in lung cancer when you are dealing with the traditional sorts of chemotherapy. These drugs are toxic to healthy cells as well as the cancer cells. After 4-6 cycles, the attitude is that you have hit the point of diminishing return - the point where the drugs are more toxic on the healthy cells and are actually more dangerous than helpful. At the 4-6 cycle point, the risk begins to outweigh the benefit.
But after that point, there are still other drugs that can be given, or the doctors could give him a break on the medications and monitor closely and then go with a new drug once the cancer begins to show any progression.
It is all very overwhelming and everyone here really understands that. Understanding what all is going on helps a lot and you can learn a lot of that here. Don't hesitate to ask questions. You can also learn a TON from
www.cancergrace.org - and I'm sure others here will recommend that site to you.
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edited to add - I see you are getting a lot of good comments in another thread. Learning what you can and what things mean really will help you a lot. Knowledge is power, as they say. Just keep asking and folks will help you out. You will feel a little more in control if you at least feel like you understand things. Though everyone here can attest to the fact that nothing makes you feel quite as powerless as cancer. At least here, you can feel like you have taken back some of that power. Good luck, and hang in there. Lots of folks here to help and to support you!