Hi lybrate-user, You summarize the case very well. I understanding of your case says, he has Ca lung adenoca, treated with dCTRT, that progressed and now disseminated disease, which is not curable by any means. The goal of the treatment in such cases would be palliative only, which means to increase longevity without causing much side effects of the drugs and reduce his problem. Now going towards your questions, 1&2. At this juncture, Gene profiling is not necessary for me but to start the EGFR targeted medicines, which includes Erlotinib/Gefitinib or Afatinib. Usually patients with such mutation as in your case responded but unfortunately not for the indefinite period but averagely 6 to 10 months. On progression, you have to get the gene profiling to see the change in the mutational status. You can refer to NCCN guidelines or American cancer society information. 3. Your father should receive, targertd therapy only, no chemotherapy for sure. It is proven better than chemotherapy in terms of Quality of life and progression free survival (average duration to progress on Treatment)
4. Regarding etiology or causation of lung cancer, HBOT not implicated for such cancers. And more so any carcinogen if cause cancer, it has a reasonable time to show its effects, like you must have seen chronic (long term) smokers will develop lung cancer. HBOT cause local hypervascularization and produce free radicles, so many studies tried see its role as a carcinogen, but tilll date it is not proven carcinogen as per ICAR. Hoping it solves your query. It is nice to see a son is keen and read in-depth about his father's illness.
Good luck for further treatment.