TTF1 and small cell lung carcinoma: Wang et al[13] observed that the objective response rate was higher in TTF-1-positive patients, suggesting that TTF-1 may be a predictive marker of response to first-line chemotherapy, a finding echoed by another study.[25] This discrepancy was observed primarily in limited-stage SCLC, with no significant correlation between TTF-1 expression and objective response rate in extensive-stage SCLC.[13]