Abstract

Abstract 2053

Background:

External beam radiotherapy (RT) is the treatment of choice for many patients with localized (stage IE-IIE) MALT lymphoma, primarily based on single-institution case series. There are no specific factors favoring surgical management or addition of systemic therapy in these cases. The purpose of this study was to evaluate the association of RT used as the initial treatment strategy with survival outcomes in a population-based cohort.

Methods:

We analyzed 6,111 cases of st I/IIE MALT lymphoma of the most common anatomical locations included in the SEER database, diagnosed between 1998 and 2009. Cases identified through autopsy or death certificate only, as well as those with unknown stage or RT status were excluded. RT was recorded only if administered as part of the initial treatment strategy within 12 months of diagnosis. 5-year relative survival was summarized for treated and untreated patients. For multivariate regression, flexible parametric Royston-Parmar models for overall survival were fitted for each site, adjusting for clinical and socioeconomic confounders. Age and surgical excision of the primary site were always included as variables. No records of progression-free survival, alternative or subsequent systemic treatments or watchful waiting strategy were available.

Results:

There were significant differences in the rates of RT utilization, baseline clinical characteristics and survival outcomes. Median age varied from 57 years (cutaneous lymphoma) to 69 years (breast). In multivariate models, RT was associated with improved survival in patients with ocular, cutaneous or gastric localization with no significant association for the pulmonary, intestinal, salivary, mammary and thyroid sites. The hazard ratio in gastric MALT was non-proportional and increased from 0.45 at 6 months to 0.97 at 24 months form diagnosis. Long-term prognosis for ocular, salivary and cutaneous thyroid lymphomas was excellent, but was less favorable for the gastrointestinal or pulmonary locations.

Conclusions:

The survival benefits of RT in early-stage MALT lymphoma are most evident for ocular and cutaneous sites of origin, and this modality can be advocated for treatment. The relative survival of 99–100% in those anatomical subtypes may indicate curative potential in patients who receive RT. In gastric MALT lymphoma the benefit is limited to the early period of two years of follow up. Inferior survival despite local radiotherapy in pulmonary and intestinal locations may suggest higher rates of occult disseminated disease and potential value of systemic therapy.

Siten% receiving RT5-year relative survival (95% CI)HR for RT (95% CI)P
All patientsNo RTRT
Gastric 2499 27% 0.88 (0.86–0.91) 0.87 (0.84–0.89) 0.92 (0.86–0.95) 0.45–0.97a 0.0002 
Ocular 1013 67% 0.94 (0.89–0.97) 0.84 (0.75–0.90) 0.99 (0.46–1.00) 0.56 (0.4–0.77) 0.0004 
Salivary 615 44% 0.92 (0.86–0.96) 0.87 (0.79–0.92) 0.98 (0.47–1.00) 0.73 (0.49–1.11) 0.14 
Intestine 600 11% 0.88 (0.83–0.92) 0.88 (0.82–0.92) 0.87 (0.64–0.96) 0.79 (0.42–1.46) 0.45 
Skin 514 51% 0.98 (0.86–1.00) 0.90 (0.76–0.96) 1.00 (0.97–1.00) 0.47 (0.27–0.81) 0.007 
Lung 496 9% 0.87 (0.80–0.92) 0.87 (0.80–0.92) 0.92 (0.46–0.99)b 0.66 (0.32–1.38) 0.28 
Breast 210 41% 0.90 (0.80–0.95) 0.86 (0.73–0.93) 0.95 (0.66–0.99) 0.62 (0.31–1.22) 0.17 
Thyroid 164 49% 0.93 (0.82–0.97) 0.90 (0.74–0.96) 0.95 (0.64–0.99) 0.6 (0.25–1.41) 0.24 
Siten% receiving RT5-year relative survival (95% CI)HR for RT (95% CI)P
All patientsNo RTRT
Gastric 2499 27% 0.88 (0.86–0.91) 0.87 (0.84–0.89) 0.92 (0.86–0.95) 0.45–0.97a 0.0002 
Ocular 1013 67% 0.94 (0.89–0.97) 0.84 (0.75–0.90) 0.99 (0.46–1.00) 0.56 (0.4–0.77) 0.0004 
Salivary 615 44% 0.92 (0.86–0.96) 0.87 (0.79–0.92) 0.98 (0.47–1.00) 0.73 (0.49–1.11) 0.14 
Intestine 600 11% 0.88 (0.83–0.92) 0.88 (0.82–0.92) 0.87 (0.64–0.96) 0.79 (0.42–1.46) 0.45 
Skin 514 51% 0.98 (0.86–1.00) 0.90 (0.76–0.96) 1.00 (0.97–1.00) 0.47 (0.27–0.81) 0.007 
Lung 496 9% 0.87 (0.80–0.92) 0.87 (0.80–0.92) 0.92 (0.46–0.99)b 0.66 (0.32–1.38) 0.28 
Breast 210 41% 0.90 (0.80–0.95) 0.86 (0.73–0.93) 0.95 (0.66–0.99) 0.62 (0.31–1.22) 0.17 
Thyroid 164 49% 0.93 (0.82–0.97) 0.90 (0.74–0.96) 0.95 (0.64–0.99) 0.6 (0.25–1.41) 0.24 
a

non-proportional hazard.

b

not age-standardized due to small number of patients.

Disclosures:

No relevant conflicts of interest to declare.

Author notes

*

Asterisk with author names denotes non-ASH members.