Long-term outcomes of globe-sparing surgery combined with adjuvant radiotherapy for lacrimal gland adenoid cystic carcinoma

Purpose To evaluate long-term outcomes of radiotherapy after globe-sparing surgery for lacrimal gland adenoid cystic carcinoma (LGACC) and compare different radiotherapy protocols. Methods This retrospective comparative case series included 97 patients with LGACC treated with globe-sparing surgery followed by postoperative radiotherapy between November 2003 and April 2023. Patients received one of four protocols differing in clinical target volume (CTV) expansion and radiation dose. Primary outcomes included locoregional recurrence, distant metastasis, locoregional recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), progression-free survival, and overall survival. Results The median age was 38 years, and median follow-up was 7.2 years. The overall 5-, 10-, and 15-year LRFS rates were 80.2%, 74.5%, and 74.5%, respectively. Multivariable analysis identified R2 resection (HR = 4.16, 95% CI: 1.53‑11.35, P = 0.005), cribriform histology (HR = 0.26, 95% CI: 0.08‑0.81, P = 0.020), and smaller CTV expansion (≤0.5 cm; HR = 4.06, 95% CI: 1.41‑11.67, P = 0.009) as independent predictors of local recurrence. Patients treated with ≤0.5-cm CTV expansion and ≤54 Gy had significantly lower 5-, 10-, and 15-year LRFS rates (55.2%, 40.5%, and 40.5%) than those treated with 1-cm CTV expansion and 60-80 Gy (90.5%, 90.5%, and 90.5%; P < 0.001). DMFS did not differ significantly between groups ( P = 0.599). Best-corrected visual acuity of 20/20-20/40 was preserved in 35.1% of patients. The 5-year risk of radiation retinopathy was 25.1% and 43.6% ( P = 0.057) in the no extended-margin and extended-margin groups, respectively. Conclusions Radiotherapy with 1-cm CTV expansion and a dose of 60 Gy after globe-sparing surgery provided favorable locoregional control for LGACC. Distant metastasis remained the predominant cause of treatment failure.