ESTRO 36 Abstract Book

S567 ESTRO 36 2017 _______________________________________________________________________________________________

categorized as positive.The initial response to CRT was documented at 8 ks post CRT and patients were followed up for a minimum period of one year for locoregional control and survival.

Conclusion Elderly HNSCC patients have worse survival outcomes in relation to younger patients. Age is an ind ependent prognostic factor for OS, mainly due to an increase in non- cancer related mortality and comorbid diseases. EP-1034 Significance of mutant p53 and Ki67 as predictive biomarkers post Chemo-RT in locally advanced HNSCC P. Baskaran Shanmuga 1 , K. Periasamy 1 , S. Sharma 2 , G.K. Singh 1 , K. Pratap 1 , P. Singh 2 , V. Yadav 1 , A.K. Mandal 2 , K.T. Bhowmik 1 1 Safdarjung Hospital, Radiotherapy, New Delhi, India 2 Safdarjung Hospital, Pathology, New Delhi, India Purpose or Objective The heterogeneity in outcome following chemoradiation (CRT) in locally advanced HNSCC has drawn the attention of clinical researchers towards molecular markers. Despite almost three decades of research the role of several biomarkers remain uncertain. This study intended to speculate the significance of expression of mutant p53 and Ki67 in treatment response, locoregional control and survival. Material and Methods This prospective observational study included 62 patients with stage III-IV non- nasopharyngeal head and neck squamous cell carcinoma of which 58 patients completed CRT. Immunohistochemistry was done on the pre- treatment biopsy specimens and the expression of mutant p53 and Ki67 in the tumor were graded based on the degree of nuclear staining as negative (0%), low (≤ 20%), medium (>20% - <40%) and high (≥ 40%). For statistical analysis, negative and low expressions were categorized as negative whereas medium and high expressions were

Results 60% of the patients had p53 expression and 62% had Ki67 positivity. Positive expression of p53 and Ki67 had a statistically significant relative risk (RR) of 7.88 (p<0.001) and 3.36 (p 0.004) respectively for treatment failure at 8 weeks post CRT. Similarly, positive expression of p53 and Ki67 had a statistically significant relative risk (RR) of 6.32 (p<0.001) and 3.30 (p<0.001) respectively for locoregional failure and distant metastases at 1 year post CRT. On multivariate analysis, the absence of p53 was a statistically significant independent predictor for complete response at 8 weeks and locoregional control at 1 year post CRT with an Odds ratio of 22.90 (p 0.0001) and 32.22 (p<0.0001) respectively. Likewise, the presence of early nodal stage (N0 - N1) was a statistically significant independent predictor for survival with an Odds ratio of 11.14 (p=0.0378).Positivity of p53 and Ki67 showed a RR of 2.62 (p=0.64) and 2.44 (p=0.70) respectively, for mortality, although their values did not reach statistical significance. Conclusion The presence of p53 and Ki67 were associated with significant risk of treatment failure, poor locoregional control and distant metastasis whereas the absence of p53 and early nodal stage favored locoregional control and survival respectively. These results signify the predicitve roles of p53 and Ki67 in treatment of head and neck