A recent article about SBRT salvage after radiation therapy

This was published June 9, 2017, so it's very recent:

Salvage robotic SBRT for local prostate cancer recurrence after radiotherapy: preliminary results of the Oscar Lambret Center

It's a retrospective study with a small sample size (25 patients, including a whopping one G9). The authors present this as directionally favorable, but also provide a number of cautions and limitations. The devil is always in the details.

Here are a couple of them:
Prior radiation dose is lower than presently common practice
Nevertheless, further follow-up is needed to evaluate late toxicities. Moreover, the median dose previously delivered by EBRT was 73.8 Gy in the Fuller series and 75.6 Gy in ours, corresponding to a lower dose than that currently used for prostate cancer treatment. Increased toxicities may appear for patients previously treated by EBRT with a higher dose.

Small sample size, so it's only directional
Because of the small number of patients included in this study, no prognostic factor could be identified. Currently, no conclusions can be made on available data, but early results are promising. Prospective studies are warranted to identify which patients benefit from local treatment.

Presented for general information. Please read it yourself if you find it interesting, and draw your own conclusions.

I agree that the French study gave dosing on the cautious side, and the Fuller study, which gave higher doses (because of the heterogeneous planning), also had low amounts of toxicity and better oncological response with 2 years of follow up. As with everything using SBRT, careful adherence to dose constraints and image guidance is very important. So far, it is very encouraging. As Redwing says, the devil is in the details.

I'll make ASAdvocate's link clickable:
/pcnrv.blogspot.com/2016/08/salvage-sbrt-for-local-recurrence-after.html