Is the MRI needed now or not?

After working out on the treadmill (had not exercised in years) every day for over a month. No stretches or slow start or slow down. Hit it hard and heavy every single day for 1 - 1.7 miles. No discomfort. After 3 weeks I mentioned during my routine video visit with my family doc that (only) my gluteal muscles felt tight and sore. He said it was the treadmill and told me to not exercise so hard.

Almost 2 weeks later of the same hard treadmill exercise I woke one morning unable to bear weight on my legs due to excruciating pain in my bilateral butt, back thighs, down the leg. After a hot bath I could walk with discomfort. Doc suggested Advil and a visit. During visit took X-rays of my lumbar spine, sacrum/coccyx, and pelvis. No tumors were visualized, no problems, except the lumbar spine had the expected degenerative changes and mild retrolisthesis and mild anterolisthesis, perhaps due to my osteoporosis. Doc thought it might be sciatic pain from the mild lumbar spine age-related degenerative changes and thought it wise just to rule out a spinal tumor and ordered an MRI

I knew it was muscular pain and my back didn't hurt I'd just had my mammogram, 12 years cancer-free this week. Waiting for MRI, he sent me to physical therapy in his office who diagnosed it decidedly as Piriformis Syndrome, my first thought a couple weeks ago. The lead therapist said the diagnosis was 100% Piriformis Syndrome, but didn't feel it was their place to question the MRI because I could have a metastasis anywhere in my body at any time. I'm confused now I just don't see how a lumbar MRI with no back pain was being pursued except to cover bases because if I have a net, I could have one anywhere.

If it were you, would you go through with the lumbar spine MRI, the initial idea, if the physical therapy continued to help? Would you hold off just for now? The family doc can give no specific reason for the MRI except my history of BC Frankly, years ago I was seen only in our hospital's large Breast Clinic where I felt my care was more defined and knowledgeable, but after several years cancer-free we're sent back to our family practice and can't see the Breast Clinic

No lymph node involvement during surgery and very clear margins at cancer site. Last week was my 12th mammogram cancer free. In addition to Piriformis diagnosis (due to exercise overuse, no stretching, bad technique, no exercise for years before) do you think this could still involve lumbar spine metastasis? Thanks for helping,

Faith