FLOW CYTOMETRIC QUANTIFICATION OF THE PROLIFERATION-ASSOCIATED NUCLEAR ANTIGEN-P105 AND DNA CONTENT IN ADVANCED HEAD AND NECK CANCERS - RESULTS OF RTOG-91-08

Purpose: p105 is a proliferation-associated nuclear antigen which iden tifies proliferating but not resting cells. The objectives of this Rad iation Therapy Oncology Group (RTOG) protocol (91-08) were: (1) to cor relate tumor proliferative potential estimated using the p105 assay an d deoxyribonucleic acid (DNA) analysis with treatment outcome in patie nts irradiated for advanced squamous cell carcinoma of the head and ne ck; and (2) to evaluate the potential of p105 labeling indices as a pr edictive assay. Methods and Materials: Paraffin blocks of pretreatment biopsies of the primary tumor or metastatic neck nodes of patients wi th Stage III or IV squamous cell carcinoma of the head and neck treate d with radiotherapy alone in three previous RTOG protocols (79-13, 79- 15, and 83-13) were retrospectively obtained. From these paraffin bloc ks, areas of tumor were selected based on histological examinations an d sectioned. Nuclei suspensions were then prepared and processed for p 105 antibody and DNA staining and subsequent flow cytometric quantific ation of p105 labeling indices and DNA content and correlation with lo cal-regional control and survival. Results: Paraffin blocks of tumor b iopsies from 148 out of a total of 598 eligible patients were availabl e. Of these, 143 were analyzable. The median and (range) of p105 label ing index (LI-C), p105 labeling index of cells in S phase (LI-S), and p105 antigen density (AD) were: 66.6 (3.85-99.5), 9 (1.55-36), and 93. 2 (7.4-628.5), respectively. Deoxyribonucleic acid was diploid in 67 ( 47%), aneuploid in 22 (15%) and mixed aneuploid/diploid in 54 (38%) pa tients. There was a strong correlation between AD and DNA ploidy. Anti gen density was above median in 91.5% of the aneuploid or mixed aneupl oid/diploid tumors, but only in 8.5% of the diploid tumors. Patients w ith aneuploid or mixed aneuploid/diploid tumors had significantly grea ter local-regional failures than patients with diploid tumors (p = .01 80). Those with p105 LI-C below the median or p105 AD above the median also had significantly greater local-regional failures (p = .0500 and p = .0167, respectively). Patients with p105 AD below the median had significantly better survival than those above the median (p = .0444), although there was no significant difference in survival with respect to DNA ploidy or p105 LI-C. Multivariate analyses showed that T-stage (p = .0001) and p105 AD (p = .0044) were significant prognostic facto rs for local-regional control, and T-stage (p = .0080), N-stage (p = . 0021), primary site (p = .0110), and p105 AD (p = .0326) were signific ant prognostic factors for survival. Conclusion: These results suggest that flow cytometric quantitation of the proliferation-associated nuc lear antigen p105 and DNA content of pretreatment tumor biopsies may b e a potentially useful predictive assay in patients irradiated for adv anced squamous cell carcinomas of the head and neck.