Association between Three-dimensional Margin Assessment and Local Tumor Control in Percutaneous Lung Cryoablation of Colorectal Metastases.

Purpose To evaluate the association of two minimum ablation margin (MAM) estimation methods: manual three-dimensional segmentation and biomechanical deformable image registration (DIR) with local tumor progression-free survival (LTPFS) after percutaneous lung cryoablation of colorectal pulmonary metastases. Materials and Methods This retrospective single-institution study included patients who underwent percutaneous lung cryoablation between May 2012 and March 2023 (median follow-up, 3.6 years; range, 0.8-9.6 years). Manual three-dimensional MAM was calculated for all tumors, and DIR-based MAM was estimated in a subset with intraprocedural full-thorax imaging. Cox proportional hazards regression assessed associations between MAM and LTPFS. The primary outcome was 2-year LTPFS, with a secondary outcome of whether DIR-based MAM was associated with LTPFS. Results Thirty-eight patients (76 colorectal pulmonary metastases in 63 procedures; mean age, 58 years ± 12 [SD]; 19 female patients) were included. Technical success was 100% (63 of 63). Per-lesion LTPFS at 1 and 2 years was 87% and 84%. Five tumors (6.6%; five of 76) had no margin (0 mm), 55 tumors (72%; 55 of 76) had a MAM 0-5 mm, and 16 (21%; 16 of 76) had an MAM greater than 5 mm. Median LTPFS was 6 months for the 0-mm group and was not reached for the MAM 0-5-mm and the greater than 5-mm groups (P < .001). Receiver operating characteristic analysis for 2-year local progression yielded an area under the receiver operating characteristic curve (AUC) of 0.81 (95% CI: 0.62, 0.95). Among 36 tumors (22 patients) with full-lung imaging available, the DIR-based MAM had an AUC of 0.76 (95% CI: 0.55, 0.98), and the manual method had an AUC of 0.79 (95% CI: 0.52, 1.00). At multivariable analysis, MAM greater than 0-5 mm (hazard ratio [HR], 0.05; P < .001), MAM greater than 5 mm (hazard ratio, 0.03; P = .005), and ablation volume (hazard ratio, 0.93; P < .001) were independently associated with reduced LTP. Conclusion Quantitative MAMs are strongly associated with LTPFS, underscoring the importance of achieving adequate margins in percutaneous lung cryoablation. Keywords: Pulmonary Cryoablation, Deformable Image Registration, Colorectal Cancer, Pulmonary Metastasis, Minimum Ablation Margin © RSNA, 2026.