Hematologic Cancer

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MO_41_2571 - Radiation therapy for salivary gland MALT lymphoma: Ultra low dose treatment spares salivary function and achieves excellent outcomes

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Radiation therapy for salivary gland MALT lymphoma: Ultra low dose treatment spares salivary function and achieves excellent outcomes
J. R. Gunther1, C. Park2, S. A. Milgrom1, B. Dabaja1, R. J. Cruz Chamorro3, L. J. Medeiros4, J. Khoury5, N. Garg6, B. Amini7, M. A. Fanale8, H. Lee5, N. Fowler5, L. Nastoupil5, S. S. Neelapu5, and C. C. Pinnix1; 1The University of Texas MD Anderson Cancer Center, Division of Radiation Oncology, Houston, TX, 2Vanderbilt University, Nashville, TN, 3University of Puerto Rico, San Juan, PR, 4The University of Texas MD Anderson Cancer Center, Department of Hematopathology, Houston, TX, 5University of Texas MD Anderson Cancer Center, Houston, TX, 6The University of Texas MD Anderson Cancer Center, Houston, TX, 7Dept. of Radiology, The University of Texas MD Anderson Cancer Center, Houston, TX, 8The University of Texas MD Anderson Cancer Center, Department of Lymphoma/Myeloma, Houston, TX

Purpose/Objective(s): Radiation therapy is often used for the definitive treatment of extranodal marginal zone lymphoma (MALT lymphoma), including the salivary glands. In this study we aimed to: 1) evaluate outcomes and toxicity after radiation therapy (RT) for this disease; and 2) compare treatment with standard dose (SD) to ultra-low dose (ULD) treatment.

Materials/Methods: We identified all patients treated with RT at our institution for MALT lymphoma involving the parotid or submandibular glands from 2000-2017. Our primary outcome was local control, defined as no evidence of clinical or radiographic recurrence/progression at last follow up. We also assessed rates of xerostomia above baseline dysfunction related to autoimmune disorders (e.g. Sjogren syndrome). We then compared these outcomes for patients who received SD versus ULD treatment (defined as 4 Gy).

Results: 15 patients were identified (10 stage I, 4 stage II (regional nodes), 1 stage IV (neck, abdominal nodes). Median age at time of RT was 53 years and 11/15 were female. Five of 15 had autoimmune disease. All patients had normal serum LDH levels. Median clinical follow up for the entire cohort was 29 months (SD patients, 85 months (range 15-203); ULD patients, 5 months (range 0-29). One patient was lost to follow up directly after RT. Eight patients underwent surgical excision prior to RT (4 superficial parotidectomy, 4 excisional biopsy). At least 4 patients (2 SD, 2 ULD) had no gross disease at time of treatment (3 patients had no diagnostic imaging after resection but prior to RT). Twelve patients had FDG PET/CT, and all non-excised sites were PET avid. Median SUVmax of intact salivary MALT lesions was 7.75 (range 5.5-10.8). Nine patients received SD treatment (median 25.5 Gy, range 24-30.6 Gy) and six patients received ULD treatment (4 Gy). Baseline characteristics, including prior excision, were similar between groups. Six of nine (66%) SD patients were treated with intensity modulated radiation therapy. All ULD treatments used 3D conformal techniques. For all but one patient, the entire gland was the target. Local control was 100% for evaluated patients in both groups. In the SD group, three patients had distant relapses (untreated salivary glands, orbits, and femur). No ULD patient had distant relapses. All patients are currently alive and in remission after additional therapy (R-CVP, 1 pt; rituximab, 2 pts). Eight of 9 SD patients reported increased dry mouth above any baseline dysfunction. No ULD patient reported increased dry mouth.

Conclusion: Patients treated with definitive RT for salivary gland MALT lymphoma have excellent outcomes, with local control rates of 100%. With short follow up, ULD RT appears to result in equivalent outcomes with lower rates of xerostomia, and should be considered to spare patients treatment toxicity. Longer follow up is needed for the ULD group to confirm excellent control rates.

Author Disclosure: J.R. Gunther: None. C. Park: None. B. Dabaja: None. R.J. Cruz Chamorro: None. L.J. Medeiros: None. B. Amini: None. M.A. Fanale: None. H. Lee: None.

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