Would you consider PRRT re-treatment in a patient with a well differentiated NET previously treated with 4 cycles of PRRT?

Yes, but only for highly selected patients.

Might consider discussing retreatment with PRRT (R-PRRT) in those who:

1. Derived good response (or prolonged stable disease) with prior PRRT and,

2. Don't have better options available (for example, would not do R-PRRT before CapTem, afinitor, sutent in pNET or afinitor in sbNET) and,

3. No concerning cytopenia (brewing MDS etc).

Most of the data we have is from Europe, where re-treatment is considered in patients who had prior benefit (response and/or more than a year disease control). There have been studies looking at retreatment (R-PRRT) or even re-retreatment (RR-PRRT) (see Van Der Zwan below).

This has been done with prior Lu177 and now Lu177 or prior Y90 and now Lu177 (Sabet et al. below).

Re...

I agree with the above. Of course, quality data (in the form of RCTs) are lacking when it comes to retreatment with PRRT (rPRRT). We have typically selected patients where other therapy options are lacking, where the tumors still have a substantial and uniform somatostatin receptor expression, and where there is 18 months or more from the first cycle of the initial PRRT until progression (this is not a well validated cutoff).

Not all retrospective reports are as favorable when it comes to rPRRT. As an example, Rudisile et al., PMID 31395036 in Munich reported mPFS of only 6 months. Zacho et al., PMID 33470864 in the Aarhus group reported a more favorable outcome with mPFS of 19 months but both grade and anatomic location of the primary were ...