Stage IV NSCLC Lung Cancer

Hello,
I am sorry to hear about your wife's recent health issues.
The fact that the recent scans showed that new areas of involvement in the liver and right femur, despite stable size of primary lung lesion may indicate disease activity.
Unfortunately, stage 4 lung cancer is untreatable by current treatment methods. However, much can be done by modern chemotherapy and supportive care to improve symptoms and prolong life. The combination of platinum plus pemetrexed that she has received is indeed a standard approach.
Regarding your question about the efficacy of Tarceva (erlotinib), at this time the evidence seems to be that this EGFR blocker is effective in patients with or without EGFR mutation, although it clearly shows higher degree of benefit in patients with EGFR gene mutation. IN EGFR wild type patients (those without mutation), the benefit is very marginal. At the current time, there is no proven or very promising experimental therapy for stage 4 disease, although many targeted therapies do show incremental benefit. Please have a detailed discussion with your treating oncologist about available clinical trials in advanced lung cancer at the hospital where your wife is being treated.
All the best, and God Bless.
References:
http://en.wikipedia.org/wiki/Erlotinib
http://www.medscape.com/viewarticle/722133