Aim: This study was conducted to assess the dose-volumetric threshold of radiation induced hypothyroidism (RIHT) in patients receiving radiotherapy (RT) to the neck. Study Design: This is a prospective cohort observational study. Place and Duration of the Study: The study was conducted at Mansoura University Hospital, Mansoura, Egypt, between April 2016 until March 2019. Methods: We have completed 2 years of follow up to 50 patients with different malignancies who were treated by radiotherapy to the neck. Baseline assessment of the thyroid clinically and radiologically was done prior to the start of radiotherapy. Periodic testing of the cohort through the follow up period was done by clinical examination, measurement of TSH, fT4 and thyroid ultrasonography. Results: the incidence of RIHT was 26%. No statistical significance for the clinical risk factors. The dose-volumetric risk factors were studied and showed positive results. A mean dose of 5185 cGy was found a significant risk factor. Also, V40 ≥ 89%, V45 ≥ 63.5%, V50 ≥ 22.5% were found to be the cutoff predictors for the threshold radiation dose to induce hypothyroidism. Also decreasing the size of the gland by ≥0.7 cm3, fT4 value by ≥ 3.5 pmol/L and TSH by ≥ 0.75 uIU/L after one year from the end of EBRT is the cutoff value for prediction of occurrence of RIHT within the 2nd year of follow up. Conclusion: RIHT is a considerable late adverse effect for patients receiving RT to the neck. Mean dose, V40, V45 and V50 were found significantly related to RIHT. Mean dose of ≥ 5185 cGy, V40 ≥ 89%, V45 ≥ 63.5%, V50≥ 22.5% were proven to be the dose-volumetric threshold.

12133 Background: Management of metastatic solid malignancies is generally focused on prolonging life along with improvement of quality of life. Hence palliative intent treatment. The understanding of the disease nature and its treatment intent is variable among patients and it’s unclear what are the main contributing factors. Our study across multiple cancer centers in Egypt evaluated patients’ understanding of whether their treatment was for curative or palliative purposes and sought to identify factors associated with understanding of treatment intent. Methods: This was a survey based study of 489 consecutive patients with stage IV solid tumor malignancies at four different cancer centers in Egypt. Patients were given a questionnaire, during a routine visit. Requested information included primary site of malignancy, stage, duration of treatment, whether they think the treatment is curative, and whether they think the treatment will help them live longer and/or relieve cancer-related symptoms. Patients also provided basic demographic information such as age, gender, marital status, area of residence and education level. Their answers regarding cancer type, stage and length of treatment were compared with their medical records. Results: Median age was 53 with 67% females. Of the 489 patients, 48% finished at least middle school education. The primary malignancies consisted of 35% breast, 19% gastrointestinal/liver, 9% genitourinary, 9% lung, 8% ovarian/uterine, 11% others. 57% of patients had been on treatment for at least 6months. 45% of patients didn’t know they had a malignancy. 69% could not identify their disease stage, and only 19% of patients knew their cancer is stage 4. Only 11% of patients knew their treatment was not curative while 35% thought it was, and 53% did not know. Only 29% of patients believed their treatment would help them live longer and 62% believed the treatment would alleviate their symptoms. Younger patients were more aware of the Disease Nature (DN), however were less aware of the treatment intent (TI), compared to patients older than 60yo (P value 0.02). Urban residents answered more accurate DN questions compared to rural residents (P value 0.01), but both had similar limited understanding to TI (P value 0.2). Education level was the most consistent factor showing difference with higher level of education correlated with better understanding of DN and TI (P value 0.01). Conclusions: In our study, only 11% of patients receiving treatment with palliative intent reported understanding the intent was not curative. Factors influencing perception of treatment goals are many and include those specific to patients (education level), their cancers, and providers (educational materials). Ongoing studies will focus on identifying factors most strongly associated with a patient’s perceived TI with development of a knowledge score.