Smoking History Decreases Survival in Patients with Squamous Cell Carcinoma of the Mouth: A Retrospective Study with 15 Years of Follow-up.

Background: The purpose of this study was to evaluate the influence of smoking history on the clinical-pathological, sociodemographic and prognostic characteristics of patients with oral squamous cell carcinoma (SCC). Materials and Methods: A retrospective cohort study was carried out with the records of 136 smokers with SCC and 68 nonsmokers with oral SCC who were diagnosed and treated at Haroldo Juaçaba Hospital (2000-2014). Data on patient sex, age, race, education level, tumor location, tumor size, lymph node involvement, distant metastasis, treatment type, marital status, method of health care access (public or private health systems) and overall survival (15 years) were analyzed by the X² test, Mantel-Cox tests and multinomial and Cox logistic regression models (SPSS 20.0, p <0.05). Results: Smoking history was directly associated with male sex (p <0.001), low levels of education (p = 0.001), tumors of the mouth and palate (p = 0.001), stage T3/4 tumors (p = 0.014), lymph node metastasis (N+) (p = 0.024), palliative treatment (p = 0.024) and receiving health care through the public health system (p = 0.006), with education level being the only independently associated factor (p = 0.039). Lower survival was observed in patients who were smokers (p = 0,002), with low levels of education (p = 0.001), who had stage T3/4 tumors (p = 0.004), with N+ (p = 0.021), and had received palliative treatment (p = 0.002). Age (>65 years old, p = 0.015) and T staging (T3/4, p = 0.033) decreased the survival of SCC patients regardless of the other factors. Conclusions: Smoking history had an independent association with low education level and a history of alcoholism, and survival was negatively associated with older age and larger tumor size, which were more prevalent in smokers.