Some chemotherapy drugs have neuropathy as a known side effect. There is little that can be done medically to reverse this, but often the nerves show recovery over time.
The hamstring is a tendon, not a nerve, however, so this may be a different matter. Certain antibiotics carry the risk of tendon rupture, so the patient should be sure to discuss this with her doctors right away. They will know if investigation is indicated.
Best wishes...
The neuropathy can be from any part of the issues you mention. You certainly could say that it is because of the Breast Cancer because that brought on the treatment, the metastisis, etc. There would be no reason to investigate and MRI is only a test and would not be of any help in evaluating "pain" when any number of causes seem to be evident. Treatment would be any of the medications for this condition. Neuropathy is often a side effect of the initial disease and / or it's treatment. If the cancer was hormone receptor positive and the pt. is on some hormone treatment, these drugs may also be the cause. Regards .....