Session Item

To find the correlation between dose received by lacrimal gland and severity of dry eye symptoms in patients receiving definitive radiotherapy for primary brain tumors.

Twenty-five patients who had received radiotherapy for primary brain tumors between January 2019 to January 2021 were retrospectively analyzed. Both the ipsilateral and contralateral lacrimal glands were contoured retrospectively using the previous registered CT images and T1 contrast MRI images as per the contouring guidelines given by Scoccianti et al. All patients were treated by the VMAT technique. The Dmax, Dmean, V40, V30, V20, and V10 for ipsilateral(I/L) and contralateral (C/L) lacrimal glands (LG) were dosimetrically analyzed. The patients were assessed for symptoms of dry eye on their follow-up visit. Common Terminology Criteria for Adverse Events version 5 was used to evaluate the severity of dry eye post radiation therapy. The Pearson chi-square test for association was used to find the association between categorical data. The odds ratio(OR) was used to correlate Grade 2 dry eye toxicity with Dmax, Dmean, V10, V20, and V40 of the Ipsilateral LG. The analyses were done using the Statistical Package for the Social Sciences (SPSS) software (version 20). A p-value of <0.5 was considered to be significant.

The Median follow-up duration was 13 months.

Based on location, 44% were frontal lobe tumors, 20% temporal, and 12% were of the parietal lobe. The remaining 24% had posterior fossa and middle cranial fossa location of the tumor. Out of 25 patients, seven patients have died. Thirteen patients (52%) had grade 2 dry eye symptoms, five patients (20%) had grade 1 dry eye symptoms.

The mean dose to tumour was 55.9 Gy ,median 60 Gy (54 to 60 Gy).Ipsilateral LG Dmax was 30.4 Gy, median 30.4 Gy(21.8-37.05 Gy), and ipsilateral LG Dmean was 17.3 Gy,median 17.8 Gy(9.9 -24.45Gy).The mean ipsilateral LG V40, V30, V20,V10 were 2.34%,16.5%,40.8%,74.5% and median were 0%,0.2%,47.3% and 95% respectively. No grade 3 toxicity was seen. The dose relationship for grade 2 toxicity was correlated for Dmax, Dmean, V10, V20, V40 of ipsilateral LG. For Dmax the OR for grade 2 toxicity was 1.01 (95% CI 0.95-1.08,p 0.695). Whereas, the OR for Dmean and grade 2 toxicity was 1.02 (95% CI 0.94-1.11,p 0.658).Similarly the OR for grade 2 toxicity was 1.02 (95% CI 0.99-1.04,p-value 0.228),1.01 (95% CI 0.99-1.03,p 0.520) and 0.95 (95% CI 0.82-1.09,p 0.466) for V10,V20 and V40 ipsilateral LG respectively.The contralateral LG Dmax dose was16.8 Gy,median14.9 (8.75 to 21.2) and Dmean was 10.2,median 7.3 (4.5 to 10.7).

The majority of the patients in the study had grade 2 dry eye symptoms, which can be attributed to the dose received by the ipsilateral lacrimal gland. There was an association between dry eye symptoms with the dose received by the ipsilateral lacrimal gland. Hence it should be marked as a vital avoidance organ in the planning of radiotherapy for primary brain tumors.