Predictive factors for isolated pulmonary metastasis in pathological T1 colorectal cancer following curative resection with lymph node dissection: a multicenter study.

PURPOSE: This study aimed to clarify the incidence and risk factors for isolated pulmonary metastases following the curative resection of pathological T1 colorectal cancer (pT1 CRC).

METHODS

We retrospectively analyzed 3171 patients who underwent curative resection with lymph node dissection for pT1 CRC at 27 Japanese institutions between 2009 and 2016. Potential risk factors were evaluated using Cox proportional hazard regression models.

RESULTS

During a median follow-up of 64 months, 21 patients (0.7%) developed isolated pulmonary metastases. The 5-year cumulative incidence was 1.2% for rectal cancer (n = 9/812) and 0.6% for colon cancer (n = 12/2359). An exploratory multivariate analysis identified rectal location and pedunculated (Ip) morphology as potential risk factors. In subgroup analyses, lymphatic invasion was associated with pulmonary metastasis in rectal cancer, whereas the Ip morphology and tumor size ≥ 20 mm were associated with pulmonary metastasis in colon cancer. Patients with rectal cancer with positive lymphatic invasion showed a 5-year cumulative incidence of 2.5% (n = 6/256). In colon cancer, patients with two identified risk factors exhibited a 5-year incidence of 5.1% (n = 5/109 patients).

CONCLUSIONS

Although pulmonary metastases are rare in this surgical pT1 CRC cohort, specific clinicopathological features appear to increase this risk. These findings may help identify candidates for future investigations of risk-adapted surveillance strategies.