346P - Analysis of various prognostic factors on local control and survival in post operative cases of malignant salivary gland tumors

Abstract

Background: The role of adjuvant therapy has not been clearly defined in certain subgroups of salivary gland tumors. Elective LN irradiation has been the subject of debate. Our study analysed various prognostic factors and the role of adjuvant radiotherapy (adj RT) in salivary gland tumors on local control and median survival. Methods: We analysed the data of 84 patients of malignant salivary gland tumors from 2010 to 2015 who underwent primary surgery at out institute with median follow up of 32 months range (3-84 months) using inclusion and exclusion criteria. None of the patients received adjuvant/concurrent chemotherapy in our study. The role of various factors like type of surgery (conservative/radical), grade of tumor, histology, PNI, margin+, LVSI+, adjuvant RT, Elective LN irradiation, LN dissection and size of primary tumor on two year local recurrence rate was evaluated as primary end point. Median survival was our secondary endpoint. Local reactions were evaluated using RTOG criteria. Stastical analysis was done using SPSS version 22.0 Results: 2 yr local control (LC) in patients who received adj RT is 88.5% and it is 37.5% who didn't receive adj RT which is statistically significant (p < 0.001) [odds ratio 10.6, 95% CI, 2.81-40.3]. High grade, LVSI+, PNI+, margin+, tumor size >4 cm and LN + have shown a trend to decrease LC rate but are not statistically significant. Interestingly, patients with LN dissection have trend towards decreased LC rate, probably due to more conservative/less aggressive LN dissection in patients who are clinically LN+. Patients with elective LN irradiation(ELNI) have a better 2 yr LC rate in high grade and large tumors than low grade and small tumors (70% vs 41%, p=.04, 64% vs 30%, p = 0.03 respectively). Adj RT doses of more than 60 Gy does not seem to improve LC in adjuvant setting and statistically not significant. The expected median survival with adj RT is 47 months vs 40 months for surgery alone(p = 0.14). Grade II reactions are 79% and 84% for xerostomia and dermatitis respectively, Grade III reactions are only 3% for radiotherapy group. There was one treatment related death in surgery alone group.Table: 346P Patients and tumor characteristicsGenderMedian- 4O yrs range- 8- 74 YRSSexMale- 38% (n = 32) Females- 72% (n = 52)SiteParotid-92.9% (n = 8) Submandibular-4.8 (n = 4) minor salivary gland-2.4% (n = 2)Surgeryconservative- 81% (n = 68) radical- 19% (n = 16)Histologyadeno CA. -14.3% (n = 12) acnic cell CA.- 7.1% (n = 6) squamous cell CA- 4.8% (n = 4) sarcoma- 4.8% (n = 4) malgnt. ex pleomorphic adenoma-2.4% (n = 2)LN dissection+43% (n = 36)pLN+7% (n = 6)Tumor size >4 CMS52% (n = 44)Gradehigh-48% (n = 40) intermediate-14% (n = 12) low-38% (n = 32)LVSI+2.5% (n = 3)Margin+7% (n = 6)PNI+7% (n = 6)Adjuvant RT72% (n = 52)Elective LNI38% (n = 32)RT dosemedian- 55 Gy RANGE- 50 -66 GyOverall 2 YR LC RATE69% (n = 58)METS+17% (n = 14) Open table in a new tab Conclusions: Adjuvant RT improves local control with trend towards improvement in survival. Elective LN irradiation in high grade and large tumors is beneficial. Radiation doses above 60 Gy doesnot seem to increase therapeutic ratio in adjuvant setting for R0 resection. Large prospective studies are needed for further evidence Legal entity responsible for the study: MNJ Institute of Oncology, Hyderabad, India Funding: None Disclosure: All authors have declared no conflicts of interest.