Chime,
Welcome here.
I am a 12-year Non-small cell, Squamous cell survivor that did not get post surgical chemo because of surgery complications. Tumors spread to my remaining lung after my pneumonectomy and my oncologist suggest the reason for the spreading was not receiving this post surgical or sometimes called "dust-up" chemo. It is designed to kill any cancer cells in the blood stream after surgery.
One can't be sure because all lung cancers, even early stage diagnosis like your dad's, have a high probability of reoccurring. Things may have changed but I was told post surgical chemo for my type of surgery was a "standard of care." I'd ask your dad's doctor if his treatment suggestion aligns with the standard of care for your dad's presentation. If it does, I'd be inclined to have the chemo. Treatments that are the standard of care provide the best probability of extended life after diagnosis.
Here is a good place to start your investigation about Squamous cell lung cancer - https://www.lungevity.org/about-lung-cancer/lung-cancer-101/types-of-lung-cancer/squamous-cell-lung-cancer
Please don't hesitate to post again if you have further questions about your dad's condition or treatment.
Stay the course.
Tom
