When the regular physician suggest you the clinical trial as your last option to extend your survival, you may be in a dilemma to get experimented with the unknown drugs. In such scenarios, taking the second opinion will strengthen your confidence regarding the treatment available in the clinical trials. People usually go for the second opinion when the diagnosis is poorly communicated, lack of other treatment options, initial diagnosis by non specialist, rare diseases, when surgery is the primary treatment and when aggressive treatment is involved.
Taking the second opinion on attend the clinical trial to treat your diseases will not hurt the feelings of the first physician, it just strengths your confidence in getting diagnosed.