Placebo

I agree - it is very curious, and I think you would agree that once this effect has been observed once, it is disingenuous for scientists to call additional examples of the same type 'spontaneous'. 

I mean spontaneous events are supposed to be unconnected with anything under consideration as a possible cure. 

Furthermore, an instance of a disease that waxes and wanes according to whether the patient is or is not given some treatment (orthodox or not) cannot reasonably be termed spontaneous.

To me, the important thing is that if even one case of cancer can be shown to be susceptible to a mental cure, serious research should be done into possible mental treatments. 

I suppose that most 'alternative therapies' could be considered 'mental.

It is of interest to oncologists and should be investigated which it is.  It's likely spontaneous cancer remission has a grounded biological explanation rather than by shear force of will. Everyone that has cancer is wishing it goes away but wishing doesn't typically reach a positive outcome. Note there are thousands of diseases that never remit no matter how hard one wishes.
Alternative therapies that work also have grounded explanations therefore become medicine. Humans bodies are machines in essence.