Can you see small, early bone cancers on an x-ray, or do they have to be already bigger tumors?

Can see early: Current radiologic diagnostic methods can detect early lesions.

There's limitation: Like any radiological testing whether mri, ct scan or bone scan, they cannot detect microscopic disease. Generally speaking, the cancer has to be about 5mm before we can say with some certainty whether it's suspicious or not. For plan xray, the bone cancer needs to have eroded the bone, cause abnormal calcification or elevate the periosteum before it's visible.