Factors Influencing the Chemo-Sensitivity of Weekly Paclitaxel for Anaplastic Thyroid Cancer: A Clinico-Pathologic Analysis of Cases Enrolled in a Clinical Trial

This study was conducted to identify the clinico-pathologic factors influencing the response to weekly paclitaxel treatment for Anaplastic Thyroid Cancer (ATC), a rare refractory disease. We investigated clinico-pathological factors as well as the expressions of Ki67, p53, MAD2, TLE3, ALDH1, β-tubulin, E-cadherin and vimentin among the subjects enrolled in a recent nationwide clinical trial of 56 patients with ATC in Japan. We compared the factors of eight responders and eight non-responders. The responders survived significantly longer than the non-responders (median 11.6 vs. 3.6 months, p=0.039). No significant between-group difference was found in histological subtype, TNM classification, or the expression of Ki67, p53, MAD2, TLE3, ALDH1, β-tubulin, E-cadherin or vimentin. When the patients' Prognostic Index (PI) was determined with the sum of four clinical factors, i.e., (1) Acute symptom within 1 month, (2) Tumor size >5 cm, (3) Distant metastasis, and (4) Leukocytosis ≥10,000/mm3, a response in the target lesion was observed significantly more frequently in the patients with a low PI score (0 or 1 positive factor) (5/5, 100%) compared to those with a high PI score (more than two positive factors) (4/11, 36.4%) (p=0.034). In conclusion, ATC patients who responded to chemotherapy with weekly paclitaxel survived significantly longer than non-responders. Patients with a low PI commonly showed a response to this chemotherapy