Enhancing precision in lacrimal sac tumor management through integration of multimodal imaging and intensity modulated proton therapy.

This study presents a patient with a PET-CT detected residual lacrimal sac tumor who was treated with intensity modulated proton therapy (IMPT) and concurrent chemotherapy. The patient a 49-year-old male diagnosed with squamous cell carcinoma of the left lacrimal sac had under-went endoscopic surgery. Postoperative PET-CT implied tumor residual in the left lacrimal sac. Given the tumor's proximity to optic organs, IMPT was employed to provide optimal dose painting. The precise delineation of the target volumes using multimodal imaging modalities (CT, MRI, and PET-CT), coupled with daily cone-beam CT technology for accurate positioning during radiotherapy contributed to an adequate dose coverage of the target. In comparison to helical tomotherapy (TOMO) and volumetric modulated arc therapy (VMAT), IMPT reduces doses to most ocular structures. With a follow-up period of 21 months after IMPT, the patient exhibited no evidence of disease recurrence and experienced only mild toxicity. This report highlights the critical role of multimodal imaging in diagnosis and radiotherapy planning. Furthermore, a literature review of proton therapy for malignant lacrimal sac tumors reveals that the scarcity of reports and emphasizes the importance of this case as a significant contribution to medical literature. This highlights the potential benefits of optimal tumor control and reducing toxicities by the integration of multimodal imaging and IMPT.