Has your light levels changed? Are you feeding on a regular basis? Is the air drier now than a few weeks ago?

Usually canes will drop all or most of their leaves when light levels change dramatically such as bringing them indoors after spending summer outdoors.

I do feed my begonias regularly. The light levels are lower in the summer months due to the sun's angle, however these plants have been in the same position for 4 or 5 years and haven't shed their leaves before. Humidity is better in the summer months with no drying heat on. I will try changing their position to a brighter spot to see if that will help. Thanks for your advice. I've never put these begonias outside for the summer mainly because I have so many others to bring in but maybe next year I will give it a try.

Just wondering is this pic Of Lana?

It is 'Silver Mist' or 'Silvermist' (see two ways to spell the same thing). It can take on many different looks depending on age and amount of light.

Indoor next to lights

Outdoor with bright sunny location.

Very nice!