Fig. 2

Kaplan Meier estimates of overall survival stratified according to smoking status in combination with HPV status. Never smokers with HPV-associated OPSCC had the best overall survival rates compared to other sub-groups (Log-rank test, pooled over strata; p < 0.001; n = 146). Pairwise statistical comparisons between patients with HPV-independent OPSCC who had no history of smoking and those that did, showed statistically significant difference between the two (Log-rank test, pairwise over strata; p = 0.021; n = 146). However, pairwise statistical comparisons between patients with HPV-associated OPSCC who had no history of smoking and those that did, showed no statistically significant difference (Log-rank test, pairwise over strata; p = 0.074; n = 146). Interestingly, pairwise statistical comparisons between patients with HPV-associated OPSCC with history of smoking and non-smokers with HPV-independent OPSCC had a rather similar prognosis with no statistically significant difference between them (Log-rank test, pairwise over strata; p = 0.286; n = 146)