Abstract: EP1159

Type: e-Poster

Presentation during EHA25: All e-Poster presentations will be made available on the on-demand Virtual Congress platform as of Friday, June 12 at 08:30 CEST and will be accessible until October 15, 2020.

Background

Population-level survival in follicular lymphoma (FL) is typically presented from the time of diagnosis. Although such estimates are informative, they may be pessimistic owing to patients who die within the initial years following diagnosis. Therefore, survival estimates for patients who have survived from a specified time since diagnosis add information related to changing survival expectations over time, especially when corrected for the life expectancy in the general population—that is, conditional relative survival (CRS). At present, statistics to inform patients and physicians on CRS in FL are sparse.

Aims

In this nationwide, population-based study, we assessed 5-year relative survival (RS) at diagnosis and for each additional year survived up to 10 years after diagnosis among FL patients in the Netherlands.

Methods

We selected all adult FL patients diagnosed between 1989-2017 from the nationwide Netherlands Cancer Registry, with survival follow-up until 2019. We computed 5-year RS at diagnosis and for each additional year survived up to 10 years after diagnosis. These analyses were performed for the overall cohort and stratified by sex, age (18-60, 61-70, and >70 years) and disease stage at diagnosis (I-II, III-IV, and unknown), and calendar period of diagnosis (1989-1995, 1996-2002, 2003-2008, and 2009-2017). Excess mortality, as compared to an age-, sex-, and period-matched group from the general population, is considered minimal when 5-year RS exceeds 95%.

Results

We included 13,002 adult FL patients (median age, 62 years; 50% males; 62% stage III-IV) in our cohort who were diagnosed in the Netherlands between 1989-2017. Overall, 5-year CRS slightly increased with each additional year survived and was 82% after ten years from diagnosis (Fig 1A). There were no sex-related differences in CRS (Fig 1B). Five-year RS from diagnosis improved over the calendar periods studied (Fig 1C). Five-year CRS remained steady over time among patients diagnosed during 2003-2008 and 2009-2016, while it increased in those diagnosed before 2003. Nevertheless, patients diagnosed from 2003 had higher CRS compared to those diagnosed before 2003. Five-year RS from diagnosis decreased with advanced age (Fig 1D) and stage (Fig 1E). The age-related survival differences persisted and became slightly larger for each additional year survived (Fig 1D). In contrast, the unfavorable prognostic effect of advanced disease stage at diagnosis largely diminished after patients had survived five years from diagnosis (Fig 1E).

Conclusion

All subgroups of patients with FL in this nationwide, population-based study continue to experience substantial excess mortality after having survived from a specified time point within ten years since diagnosis. Nevertheless, CRS gradually increased over the calendar periods studied, especially between 1989-1995 and 1996-2002. This finding might suggest that patients diagnosed in the pre-rituximab era (i.e. before 2003) might have benefited from rituximab later in their disease course. The prognostic effect of age persisted as more years since diagnosis passed, whereas it largely disappeared for disease stage. CRS data provide patients with essential information about their prognosis during follow-up. This information is also relevant to physicians for surveillance and follow-up activities in this era.

Session topic: 18. Indolent and mantle-cell non-Hodgkin lymphoma - Clinical

Keyword(s): Epidemiology, Follicular lymphoma, Survival