D. Zitser1, A. L. Schwer2, S. V. Dandapani3, J. Y. C. Wong3, N. Khan4, A. Kallam4, S. Kambhampati4, M. Mei4, J. Baird4, A. Borogovac5, G. Shouse4, A. Herrera4, T. Siddiqi4, L. E. Budde4, A. Amini3, and C. J. Ladbury3; 1Western University College of Osteopathic Medicine, Pomona, CA, 2Department of Radiation Oncology, Lennar Comprehensive Cancer Center, City of Hope National Medical Center, Irvine, CA, 3Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA, 4Department of Hematology and Hematopoietic Cell Transplantation, City of Hope National Medical Center, Duarte, CA, 5Department of Hematology and Hematopoietic Cell Transplantation, Lennar Comprehensive Cancer Center, City of Hope National Medical Center, Irvine, CA
Purpose/Objective(s):Involved site radiation therapy (ISRT) is the NCCN-guideline-preferred first-line treatment for early-stage gastric marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) that are either H. pylori negative or H. pylori positive but refractory to H. pylori eradication therapy. Alternative treatments include systemic therapies such as rituximab +/- chemotherapy in cases where ISRT is contraindicated, though these approaches have less favorable response rates and increased toxicity. Real-world utilization of these first-line treatments is not well characterized. Materials/
Methods: We conducted a retrospective analysis using the National Cancer Database for patients with Stage I or II gastric MALT lymphomas diagnosed between 2013-2021. Due to limitations on how rituximab was coded prior to 2013, we excluded data from previous years. Patients were classified as receiving any combination of chemotherapy (CT), rituximab (R), or radiation (RT). To remove patients who were treated with H. pylori eradication therapy alone, patients who did not receive chemotherapy, rituximab, or radiation were excluded. For analysis purposes, chemotherapy and rituximab were grouped as “systemic therapy” (ST). Trends in the choice of treatment were assessed using linear regression and multivariable (MVA) logistic regression. Results: A total of 3473 patients met inclusion criteria, with 2693 (77.5%) receiving RT alone, 158 (4.5%) receiving RT + ST, and 622 (17.9%) receiving ST alone. Systemic therapy regimens included R alone in 508 (14.6%) patients, CT alone in 138 (4.0%) patients, and R + CT in 134 (3.9%) patients. From 2013 (79.0%) to 2021 (81.9%) there was no significant change in the percentage of patients receiving RT (slope 0.3%/year; p=.162), with proportions never going outside 79.0-84.8%. Among the patients receiving RT, the most common doses delivered were 30 Gy (60.0%), 30.6 Gy (14.1%), and 24 Gy (5.5%). Only 0.9% of patients receiving radiation were treated with a dose of 4 Gy. On MVA, populations that were significantly less likely to receive RT included patients who were older (OR: 0.98; p<0.001), stage II (OR: 0.33; p<.001), or with an income <$63k (OR: 0.66; p<.001). Treatment at a community hospital (Ref: academic; OR: 1.22; p=.035) was associated with increased probability of receiving RT. Year of diagnosis, sex, race, ethnicity, Charlson Deyo score, insurance, and facility volume were not significantly associated with receipt of RT. Conclusion: Nearly a fifth of patients with early-stage gastric MALT lymphoma in this real-world cohort did not receive ISRT and were treated with systemic therapy alone. Older and low-income patients in particular were less likely to receive ISRT. Though ISRT is not suitable for all patients, future work is warranted to investigate the cause of underutilization and identify means of overcoming barriers to receiving ISRT for early-stage gastric MALT lymphomas.
