Top Line: The biggest tumor board / prior authorization challenge to ablative radiation for oliomets remains the lack of high level data (read: big prospective numbers).
The Study: The NHS comes to the rescue, with the forethought to initiate in 2015 a prospective observational study across 17 institutions in England. The downside, of course, is there’s no standardized comparator in this single-arm study. But still this behemoth is chock full of prospective(!) real-world data on 1422(!) patients receiving 24-60 Gy in 3-8 fractions for metachronous oligomets, defined here as 1-3 extracranial mets with a disease-free interval from primary tumor diagnosis of at least 6 months. Given the indication for treatment, meeting dose constraints was prioritized over coverage in all scenarios, As such, the most common grade 3 toxicity was fatigue occurring in 28 patients (2%)—one might wager the same would occur in a similar no-radiation group—and the most common grade 4 toxicity was increased liver enzymes occurring in a whopping 9 patients (0.6%)—again, hard to say what the rate might have been in the setting of untreated liver mets. Importantly, overall survival at one and two years was 92% and 79%, respectively, in this fairly unselected real-life population. By now it should be hard to argue that ablative radiation for oligomets is either toxic or achieving local control in vain for a rapidly dying population. When it comes to questioning its cost, the real question should be: what’s the alternative? As the authors point out, when compared with most systemic therapies, radiation is “a non-invasive outpatient treatment that has minimal toxicity and excellent local control with high acceptability in terms of convenience and societal costs.”
TBL: As of March 2020, ablative radiation for oilgomets is now offered by the NHS to patients who fit inclusion on this study with progressive expansion due to include all radiation providers in England by 2022. | Chalkidou, Lancet Oncol 2020