Assessing actionable radiological features on serial CT images in Post-SABR patients with resected local recurrence of colorectal lung metastases.

OBJECTIVE

Diagnosing local recurrence (LR) of colorectal lung metastases (CLM) after stereotactic ablative radiotherapy (SABR) is complex; both by distinguishing benign radiological changes from LR on imaging and challenges in obtaining pathological confirmation. Actionable radiological features (aRFs) have been proposed for an earlier diagnosis of post-SABR recurrences in the lung.

METHODS

We retrospectively studied patients who had undergone salvage surgery after primary SABR for a CLM between 2014 and 2023 and with pathologically proven LR. Two thoracic radiation oncologists separately assessed all available pre-SABR and follow-up chest CT-scans to identify aRFs. Presence of the following aRFs were scored: Sequential enlarging opacity; bulging margin; craniocaudal growth; loss of linear margin; loss of air bronchogram. LR was suspected if ≥ 2 aRFs were present.

RESULTS

Seventeen lesions met study eligibility criteria. Median time to salvage resection was 26 months post-SABR (IQR:19-31). Local recurrence was suspected using aRFs in 15 lesions (88%). Suspected LRs were identified at a median of 11 months before salvage surgery (IQR:4-16). The commonest aRFs scored before salvage resection were bulging margin (94%), sequential enlarging opacity (82%), and craniocaudal growth (76%).

CONCLUSION

In patients with recurrent CLM post-SABR, 88% had aRFs indicating LR on pre-surgery CT-thorax. Local recurrence was identified 11 months earlier based on the presence of ≥2 aRFs. These findings demonstrate that aRFs are present in most patients with LR and using aRFs may allow for an earlier and imaging-based diagnosis.