Characteristics of population.

aThe survival information of 3 patients was not available in German cohort, so these 3 patients were removed from analyses.bFor one patient with liver metastasis in the Maryland cohort, the exact stage of this patient is unclear, so this patient was removed from Fisher's exact test. Because this patient already had liver metastasis, the tumor stage was treated as over IIB in the Cox regression.cT-test for comparison of Gemany and Maryland cohorts.dFisher's exact test for comparison of Gemany and Maryland cohorts.