Can metastatic lung cancer be managed with just chemotherapy?

Hi doctor,

I wanted to know how long my father could survive with chemotherapy. My father was diagnosed with metastatic NSCLC (lung cancer) two months before, and he already took two cycles of chemotherapy, one in the first week of the last month and another in the last week of the month. There has been no extreme side effect till now. The doctor also suggested a combination of chemotherapy with immunotherapy. Still, they said the clinical trial suggested that if he can tolerate immunotherapy, it should continue for at least two years. As we are from a middle-class background, continuing immunotherapy for two years is impossible. So my question is, are there any partial benefits we can get if we use immunotherapy for six to eight months along with chemotherapy and then continue only with chemotherapy?

Currently, he is taking Carboplatin–pemetrexed as a chemotherapy medicine. I am asking this question as a second opinion to maximize my father's survival within our limited financial budget. Also, I want to know how long he can survive with chemotherapy alone.

Kindly help.

Hi doctor,

Do you think partial Immunotherapy (for six months) or a low dose (if the cost is affordable) of Immunotherapy will not benefit my father's case? Or is there any bad impact if we take a shorter period of immunotherapy?