Conditional relative survival of oral cavity cancer: Based on Korean Central Cancer Registry.

OBJECTIVES: Conditional relative survival (CRS) describes the survival chance of patients who have already survived for a certain period of time after diagnosis and treatment of cancer. Thus, CRS can complement the conventional 5-year relative survival, which does not consider the time patients have survived after their diagnosis. This study aimed to assess the 5-year CRS among Korean patients with oral cancer and the related risk factors. MATERIALS AND METHODS: We identified 15,329 oral cavity cancer cases with a diagnosis between 1993 and 2013 in the Korea Central Cancer Registry. The CRS rates were calculated according to sex, age, subsite, histology, and stage at diagnosis. RESULTS: The 5-year relative survival was 57.2%, and further analysis revealed that the 5-year CRS increased during the first 2years and reached a plateau at 86.5% after 5years of survival. Women had better 5-year CRS than men after 5years of survival (90.0% vs. 83.3%), and ≤45-year-old patients had better 5-year CRS than older patient groups (93.3% vs. 86.4% or 86.7%). Subsite-specific differences in 5-year CRS were observed (tongue: 91% vs. mouth floor: 73.9%). Squamous cell carcinoma had a CRS of 87.3%, compared to 85.5% for other histological types. Localized disease had a CRS of 95.7%, compared to 87.3% for regional metastasis. CONCLUSION: Patients with oral cavity cancer exhibited increasing CRS rates, which varied according to sex, age, subsite, histology, and stage at diagnosis. Thus, CRS analysis provides a more detailed perspective regarding survival during the years after the initial diagnosis or treatment.