Lyne, in regards to this specific patient, the answer depends to a great deal on exactly what is meant by "the other treatments did not work". We would need details on exactly what was tried and what interfered with the progress. Often, I find that patients say they have tried many different approaches when actually they saw a number of different therapists but only went a time or two and never really followed through on the treatment approach. I would certainly want to know whether this patient saw a professional who specializes in anxiety disorders and followed through on treatment for a reasonable length of time.
In general, I find a variety of outcomes possible with a focussed cognitive-behavioral approach to panic disorder. As I explain to all my patients, no one can guarantee that any patient will become anxiety-free, since anxiety is part of the normal range of human experience. I cannot even guarantee to patients that they will never have another panic attack, since that is also part of the normal range of experience. Anyone can have an panic attack under the proper conditions. So, to some extent, we are all in the position of learning to cope with anxiety rather than being rid of it completely. However, Barlow's outcome studies consistently show that well over 80% of patients treated with 12 sessions of his Panic Control Treatment are panic-free at the end of the 12 sessions and remain panic-free one to two years later.
In my own clinical experience, I find that the outcomes do vary. Some patients become completely panic-free and stay that way. Other patients may have an occasional panic attack, especially under high stress, but the intensity and frequency are so much reduced that they do not interfere with the patient's life at all. When the patient learns to accept that their body may react to high stress with an occasional panic attack, but they have learned to deal with it in ways that do not make it worse than it needs to be, the panic can actually serve a useful function (as a wake-up call that maybe they need to pay attention to their stress or lifestyle).