Is surgery a treatment option for adult scoliosis?

Yes, it is an option: Whether it is necessary, or indicated is a different question. Surgery for scoliosis is a very invasive and painful surgery and usually is done when the angle gets to be too great to the point where it threatens other organs, most notably threatening respiratory status (lungs). While it is an option, it would be difficult to convince an ortho spine specialist to do the surgery unless indicated.