Prognostic impact of primary tumor location in patients with metastatic colorectal cancer (mCRC) at the salvage lines.

Abstract

741 Background: Recently it has been suggested that primary tumor location may have a clinical impact on the front line chemotherapies; namely, right-sided tumor benefit less from cytotoxic and targeted agents compared with left-sided tumor. Regorafenib and TAS 102 have recently emerged and the prognostic impacts of tumor location on these agents are unknown. Methods: Clinical information of patients who were administrated Regorafenib and/or TAS 102 was retrospectively collected. Patients’ demographics by tumor location were compared using Fisher’s exact test. Time to treatment failure (TTF), and overall survival (OS) by tumor location were calculated using Kaplan-Meyer Methods and compared using Log-rank test. In addition, subgroup analyses were performed to see the interactions between tumor location and covariates in each agent. All tests were performed at the two-sided .05 significance level. Results: The median TTF (mTTF) and OS (mOS) were 2.0 and 8.0 months in the regorafenib group (n = 98) and were 2.4 and 7.9 months in the TAS102 group (n = 95), respectively. In the regorafenib group, 71 patients had a left-sided tumor and 27 patients had a right-sided tumor. In the TAS102 group, 64 patients had a left-sided and 31 patients had a right-sided tumor. There was no significant difference between right and left sides in both groups with the exception that a greater number of older patients was seen in right-sided in the TAS102 group. No significant difference of TTF and OS by primary site were observed in regorafenib (HR 0.92, 95% CI 0.68-1.70, P = 0.71 for TTF, HR 1.09, 95% CI 0.68-1.81, P = 0.74 for OS) and in TAS 102 (HR 0.84, 95%CI 0.53-1.36, P = 0.48 for TTF, HR 1.26, 95% CI 0.72-2.33 P = 0.43 for OS). Significant interactions were shown between presence of liver metastasis and tumor location both in TTF and OS in regorafenib (p < 0.05). On the other hand, in TAS102, significant interactions were shown between period from 1st line chemotherapy and tumor location in TTF and between time to metastasis and tumor location in OS (p < 0.05). Conclusions: In contrast to front line chemotherapy, no clinical impact of tumor location was demonstrated at the salvage lines in mCRC.