Does pathologic response equate to clinical response following SABR for early-stage NSCLC?

We applaud the recent efforts of Palma et al. for prospectively addressing a novel issue regarding pathologic response following stereotactic ablative radiotherapy (SABR) for early-stage non-small cell lung cancer (1). This was a phase II trial evaluating the addition of neoadjuvant SABR prior to resection for purposes of evaluating the pathologic complete response (pCR) rate following SABR. This is of academic interest because the vast majority of SABR candidates are inoperable, and hence the pathologic response of SABR is largely not able to be assessed. The primary findings were a low (60%) pCR, highly discordant with the well-validated ≥90% local control (LC) in the irradiated lesion following modern, volumetric image-guided SABR (2-4). Although the low pCR may be concerning for many readers, there are several assuaging caveats worth highlighting.