Stereotactic Radiation - Anecdotes and Impressions

[Paul Edwards]

The Pilot study of Patients with Oligometastases from Prostate cancer treated with STereotactic Ablative body Radiosurgery (POPSTAR) trial is no longer recruiting.  I was at Peter Mac for one of my regular follow-up visits (21 months after stereotactic radiation).

 

No results have been published for this study but apparently some trends are developing.  

 

Talking to my radiology oncologist I got the impression that, although the stereotactic radiation had successfully sterilised the metastases being treated, many of the patients (including me) had further metastases develop.  There were a few patients who had not had any recurrence after their treatment.

 

Were the patients on the study who progressed after stereotactic radiation truly oligometastatic? Or did we already have the further metastases which did not show up on imaging at the time but are being detected now by improved imaging technology?

 

I’ve recently read a study* which said that it is important to define the true oligometastatic stage and suggests that there are differences between polymetastatic, oligometastatic, or oligo-recurrent disease.  The study said that a patient who is oligometastatic on diagnosis is not the same as one who is oligometastatic after treatment.

 

Poly = many.  Oligo = few.

 

Improvements in imaging (eg Ga⁶⁸ PET Scans) are going to make easier in the future to define the true oligometastatic stage.

 

In my opinion (I’m not a doctor) there is a benefit in sterilising known metastases with stereotactic radiation even in cases which are not truly oligometastatic.  Although not curative, this treatment reduces cancer load in the body, eliminates a potential source of further metastases and hopefully delays progression of the cancer.  My radiology oncologist says that he’d like to think this too but at present we don’t have any evidence.

 

* Oligometastases in prostate cancer: restaging stage IV cancers and new radiotherapy options Moreno et al. Radiation Oncology2014,9:258 http://www.ro-ournal.com/content/9/1/258

[Paul Edwards]

I had a discussion today with my medical oncologist about stereotactic radiation.  He's had several patients who've had stereotactic radiation suffer bone fractures near the radiation site.  His view is that stereotactic radiation is not suitable for everybody and that patients need to be carefully chosen for the treatment.