When staging prostate cancer, does MRI pelvis/prostate replace CT A/P?

The NCCN guidelines and recent NRG protocols allow for either CT or MRI to stage the pelvis. Assuming the MRI includes imaging of the pelvic LNs, I am not aware of an added benefit of a CT.

With the increasing use of novel imaging for staging such as PSMA PET (which can be more sensitive at detectin...

Yes. As @Dr. First Last pointed out, NCCN staging allows CT or MRI to evaluate the pelvic lymph nodes, as these are roughly equivalent in terms of sensitivity and positivity.

The MRI gives added information re: ECE, involvement of neurovascular bundle, and SVI. MRI has been proven to be better for a...

No, not for all patients. Just getting one is reasonable for most patients, especially lower, favorable intermediate risk patients.

So if a patient shows up with a CT abd/pelvis, in my clinic almost no patient that is a candidate for an MRI doesn’t get one. This is for assessing boost volume and t...

The fundamental component of the question relates to what is "staging".

Staging at its core is a system to prognosticate patients, or to risk stratify them. AJCC in the USA is the most commonly used compendium of cancer staging systems to provide a unified method of communication. Stage I has a bett...

We obtain MR to evaluate the prostate and CT to evaluate the nodes and upper abdomen. So the MR replaces the CT to evaluate the prostate but not necessarily the nodes and not the upper abdomen.