Would you treat someone following FLAME protocol for prostate cancer without fiducials if using daily CBCT?

The underlying concept within this very practical question is how we rely on on-board imaging for target localization. In my practice, in which I have high confidence in my GTV contouring accuracy and daily setup, I would feel very comfortable using CBCT instead of fiducials.

My ideal process includ...

Yes, I do it all the time. I treat with fiducials in patients who elect to have a spacer placed and without fiducials in the others. Both groups get focal RT tumor boost. We estimate the difference in daily setup accuracy at our center is 1 mm more confidence with fiducials (an additional benefit is...

If you think about it, there is no way to know how good an alignment is truly. IMO, the most objective way to get at this is to study the technology/technique via test-retest by a single observer and inter-observer variability among at least two observers. I did such a study several years ago Goff e...

There can sometimes be a not-insignificant pitch variability, as noted by others here. Pitch misrotation can cause anterior or posterior misalignment at the bladder and urethra even if well aligned at midgland prostate and even with a spacing gel in place to spare the rectum. So great care must be t...

Fiducials improve the fidelity and interoperator reproducibility of an IGRT match, definitely preferable vs CBCT alone if you can have them placed.