Phase II Trial Comparing Stereotactic Body Radiotherapy Versus Active Surveillance for Oligometastatic Adenoid Cystic Carcinoma

The oligometastatic state represents a potentially distinct phase of cancer dissemination in which eradication of all visible metastatic disease may alter subsequent disease progression. Prospective randomized trials in several solid tumors have provided evidence supporting this paradigm. In the phase II SABR-COMET trial, patients with a controlled primary tumor and 1-5 metastases randomized to comprehensive SABR had longer overall survival than those receiving standard treatment alone (median 41 vs 28 months; HR 0.57). Long-term follow-up demonstrated a 5-year overall survival of 42.3% with SABR versus 17.7% with standard treatment. There is robust prospective evidence that metastasis-directed therapy can modify the course of oligometastatic disease; however, their findings cannot be directly extrapolated to adenoid cystic carcinoma (ACC), which has distinct tumor biology and natural history.

A recent retrospective study has demonstrated that patients with oligometastatic ACC had more favorable outcomes than patients with higher metastatic burden, and that early initiation of local treatment was associated with improvement in PFS. However, these observations are subject to selection and other inherent biases of retrospective studies and cannot establish that local ablative therapy itself improves survival or progression-free survival.

The SABR Oligo-ACC Trial is therefore proposed as a randomized, phase II study comparing early initiation of SBRT to all metastases versus active surveillance in patients with oligometastatic ACC.

90 patients with histologically confirmed ACC of any primary site along with oligometastatic disease (1-5 active radiologically detectable extracranial metastatic lesions involving one or more organs) will be participating in this study.

They will be randomized (computer-generated randomization system) in a 1:1 ratio to either Stereotactic Body Radiotherapy (SBRT) or Active Surveillance.

Arm A=SBRT to all oligometastasis Arm B =Active surveillance Overall survival (OS), Progression Free Survival (PFS), Local Control of metatstatic lesion, SBRT toxicity (CTCAE version 5.0) and Quality of life (EORTC QLQ C-30) will be assessed at different timelines.