Prognostic importance of p16 status for women with vulvar squamous cell carcinoma (SCC) treated with radiotherapy

• Published in: Journal of clinical oncology Vol. 35; no. 15_suppl; p. 5599
• Main Authors: Lee, Larissa Janeen, Howitt, Brooke E., Oliva, Esther, Zhang, Hongkai, Catalano, Paul J., Crum, Christopher, Bu, Paula, Cimbak, Nicole, Demaria, Rebecca, Murphy, Rita, Horowitz, Neil S., Matulonis, Ursula A., Russo, Andrea Lyn
• Format: Journal Article
• Language: English
• Published: 20.05.2017
• ISSN: 0732-183X; 1527-7755
• DOI: 10.1200/JCO.2017.35.15_suppl.5599

Abstract only 5599 Background: To evaluate the association between p16 status and in-field recurrence (IFR), progression-free (PFS) and overall (OS) survival in patients with vulvar SCC treated with radiation (RT) with or without surgical resection. Methods: In a multi-institutional retrospective cohort study, we identified 105 women with vulvar SCC who received RT between 1985-2011. Immunostaining for p16 was performed on archival tumor tissue using the Leica Bond III staining platform. Histopathology and p16 stains were reviewed by pathologists with expertise in gynecologic cancer; the intensity and extent of p16 staining in tumor cells were classified as negative (focal, weak, patchy) or positive (moderate or strong diffuse linear positive). Actuarial estimates of PFS, OS and IFR were calculated using the Kaplan-Meier method and compared by the logrank test. Multivariable analysis (MVA) was performed using the Cox proportional hazards model. Results: Patients with p16-positive disease were significantly younger at diagnosis (median 67 vs. 77 years) and were more likely to be current smokers (51% vs. 0%) and to have received concurrent chemotherapy (68% vs. 47%, all p<0.05). FIGO stage distribution, RT intent and median RT doses were similar by p16 status. With a median follow-up of 61 months, 5-year PFS and OS rates were 35% and 40%, respectively. Women with p16-positive tumors had significantly better 5-year PFS and OS rates than those with p16-negative tumors (61% and 23%, p<0.01 and 64% and 29%, p=0.01, respectively). The 5-year IFR rate was also lower for those with p16-positive disease (17% vs. 65%, p<0.01). On univariate analysis, use of concurrent chemotherapy was not associated with PFS (p=0.5), OS (p=0.3) or IFR (p=0.8). On MVA adjusted for age and stage, p16 positivity was significantly associated with better PFS (HR 0.57, 95% CI 0.33-0.97) and lower IFR (HR 0.24, 95% CI 0.09-0.6). Conclusions: In a multi-institutional setting, women with p16-positive vulvar SCC treated with RT had a lower IFR rate and longer survival than those with p16-negative disease. The magnitude of prognostic importance of p16 status is similar to that seen in oropharyngeal, anal and cervical cancers treated with RT.