Radiotherapy as a curative strategy for primary pleural indolent lymphomas: Analytical guidelines based on literature and an illustrative population-based case series

BACKGROUND: Primary pleural indolent non-Hodgkin lymphomas, such as marginal zone lymphoma and follicular lymphoma, are rare and understudied. When truly localized, these entities are theoretically curable with radiotherapy, as is the case for other extranodal indolent lymphomas (e.g., orbit, stomach, lung). However, due to their low incidence and frequent diagnostic delays related to nonspecific clinical and radiologic presentations, no standard therapeutic recommendations currently exist. The role of radiotherapy in this setting remains undefined, even in expert guidelines. METHODS: We performed a narrative literature review and complemented these findings with a descriptive population-based case series extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Based on these findings and institutional expertise, we developed practical radiotherapy recommendations. RESULTS: Published cases show heterogeneous management strategies, with radiotherapy infrequently used but consistently associated with complete responses. In the SEER cohort, seven patients with stage I-II primary pleural indolent B-cell non-Hodgkin lymphoma (three with a marginal zone lymphoma, three with a follicular lymphoma, and one with a lymphoplasmacytic lymphoma) underwent radiotherapy. Median age was 76 years. With a median follow-up of 91 months (range: 47-172 months), the 10-year cause-specific survival rate was 100 %, and overall survival rate was 83.3 % (95 % confidence interval: 0.583-1.0 %). We propose delivering a dose of 24 to 30Gy for curative intent, with reduced-dose strategies (e.g., 2×2Gy with response-adapted completion) in selected patients. Target volumes should encompass the entire pleural mass with 2 to 3cm clinical target volume margins, using advanced planning techniques to minimize cardiac and pulmonary exposure. CONCLUSIONS: This is the first population-based study evaluating radiotherapy outcomes for primary pleural indolent non-Hodgkin lymphomas. Radiotherapy appears to be a relevant curative option for localized disease. In the absence of formal guidelines, these findings and proposed recommendations may help inform clinical management of this rare but potentially curable lymphoma subtype.