Irinotecan and radiation in vitro and in vivo

Loss of chromosome sequences at 13q14 (Rbl) and 17p13 (p53) associated with squamous cell carcinoma of head and neck (SCCHN) was evaluated in 12 recurrent tumors and 51 primary tumors from 63 patients. The incidence of LOH at 17p13 was 19 of 50 (38%) tumors, and at 13q14 was 21 of 57 (37%). LOH affecting Rbl and/or p53 was observed in 30 of 63 (48%) SCCHN. Coincident LOH at Rbl and p53 was detected in 10 of 46 (22%) tumors. There were nine cases in which primary and metastatic tumors were obtained from the same patient. Of these, seven were informative and five of these (71%) manifested LOH at p53 in both primary and metastatic sites. Examination of Rbl in these same tumors showed LOH in six of the nine metastases, and of these six, only three revealed LOH in the primary tumor. LOH at p53 or Rbl alone showed no correlation with clinical outcome. However, tumors that manifested LOH at both loci were associated with poorer patient outcome and poorer histological differentiation.