My bone cancer cured 6 yrs ago with chemo and operation.and two yrs after lung metastasis operated...what is the chances of cancer in future?

High: I'm sorry to say that your chance of more cancer is high. I'm not sure if your first cancer was a bone sarcoma, or if that was metastasic from a first cancer. Either way, once you develop metastatic disease, cancer usually isn't curable. There are some exceptions, like testicular cancer. Ask your doctor for an honest prognosis.

Chances are good: While it is obviously difficult to tell, specifically, the greatest predictor of survival chance at time of recurrence is the length of time until recurrence. The greatest predictor of cure is the length of time without a recurrence. Your history is unusually good in both regards. I would not give up on medical school, yet.

Roughly 50/50: 5 year disease free survival is around 50%. If you have a recurrence, repeat surgery is often possible and successful.

Significant!: With bone cancer, spread to the lungs is not good but there is still a significant chance for cure. The interval of 4 years between the primary tumor and the lung metastases is a good sign as is the current 2 years of being cancer-free. Close followup with your physicians is vital as additional lung nodules should be resected if they occur as there can be cures even after multiple tumors.

Depends: Could be as high as 50%. However, re operation can have excellent results.