Are you sure your tumor is small cell lung cancer? Because recommended treatement for small cell lung cancer is radiotherapy and chemotherapy
not surgery. And are you receiving these treatment.
Small cell lung cancer has high chance of spread to liver- have you undergone test like ultrasonography
or CT scan of abdomen for test of liver?
Regarding pain medication if your pain is well controlled you can stop tramadol/acetaminophen
and switch to ibuprofen.
Discuss with your oncologist
regarding changing drugs.