Introduction
The risk factors for synchronous lymph node metastasis (LNM) in pT1 colorectal cancer (CRC) are submucosal invasion depth (≥1000µm), lymphovascular involvement (LVI), poorly differentiated components (por), and tumor budding (BD). On the other hand, in pedunculated lesions with invasion confined to the head of the polyp, the incidence of LNM and recurrence have been reported to be very low (0-2.4% and 0%, respectively).1,2 However, the robust evidence has been limited.
Aims & Methods
This retrospective study aimed to compare the incidence of LNM and recurrence between the head and stalk invasion groups, based on submucosal invasion assessment using Haggitt Level 2 (HL2; the junction line between normal and neoplastic epithelium), and to evaluate the impact of LNM/recurrence risk factors in pedunculated pT1 CRC.
Patients with pedunculated pT1 CRC treated by endoscopic or surgical resection in our hospital between January 2010 and December 2021 were included. Those with multiple invasive CRCs, synchronous advanced cancer in other organs, and familial adenomatous polyposis were excluded. The submucosal invasion was classified into two groups, head invasion (above HL2) and stalk invasion (beyond HL2). Clinicopathological characteristics, incidence of LMN, and recurrence rate were analyzed between patients with head and stalk invasion.
Results
The study included 66 patients with 66 lesions. The median age was 67 years, and 52 patients (78.8%) were male. The median tumor size was 20mm, and the location was as follows: 4 lesions (6.1%) in the right colon and 62 lesions (93.9%) in the left colon. There were 40 head invasion and 26 stalk invasion lesions. There were no significant differences between the two groups for LVI (17.5% vs 26.9%), por (2.5% vs 7.5%), and BD (5.0% vs 7.7%). Surgical resection was performed more frequently in the stalk invasion group (20% vs 77%, P < 0.01). Synchronous LNM was observed in 2 patients in the head invasion group (5.0%, 95% confidence interval [CI] 0.6-16.9), and 1 patient in the stalk invasion group (3.8%, 95%CI 0.1-19.6) (P = 1). Recurrence was observed in 1 patient in the head invasion group (2.5%, 95%CI 0.1-13.2), and 1 patient in the stalk invasion group (3.8%, 95%CI 0.1-19.6) (P = 1), both of them were distant metastasis. In patients without LVI, por, nor BD, there was no LMN in either group, but recurrence was observed in 1/32 patients in the head invasion group (3.1%, 95%CI 0-17.1), and 1/16 patients in the stalk invasion group (6.3%, 95%CI 0-30.3) (P = 0.61). The patient with recurrence in the head invasion group without LVI/por/BD revealed multiple liver metastases one year after endoscopic resection, and he received chemotherapy but died of colon cancer one and a half years after recurrence.
Conclusion
In pedunculated pT1 CRC, synchronous LNM and recurrence were observed in the head invasion group, with no significant difference from the stalk invasion group. Among cases without LVI/por/BD, there was no LNM but recurrence was observed in both of head and stalk invasion groups. Contrary to the previous reports, head invasion was not a completely LNM/recurrence-free condition, so endoscopic resection alone cannot be considered curative.
References
- Matsuda T, et al. Risk of lymph node metastasis in patients with pedunculated type early invasive colorectal cancer: A retrospective multicenter study, Cancer Sci. 2022;102:1693-1697.
- Asayama N, et al. Long-term outcomes after treatment for pedunculated-type T1 colorectal carcinoma: a multicenter retrospective cohort study, J Gastroenterol. 2016;51:702-710.