@cindylb my heart goes out to you and your husband.
My wife is a stage 4 lung cancer patient, having had a double lobectomy in 2015. After not responding to opdivo treatments, her Mayo oncologist ordered a fresh lung biopsy and sent it off for a molecular study to determine the exact type of mutation.
The results were that her molecular study of the biopsy identified amplification of HER-2...common in breast cancer patients, but rare in lung cancer.
Treatment was changed to a trial doublet of meds...which she has responded to well.
Therefore, my only suggestion is to consult with your Husband’s oncologist about whether it might be worth pursuing a molecular study to define the exact mutation to better establish the correct treatment path.
Good luck!