PD-L1 and histopathological subtype have no impact on survival after whole brain irradiation
PO-1446
Abstract
PD-L1 and histopathological subtype have no impact on survival after whole brain irradiation
Authors: Filippa Sundbye1, Kristin Skougaard2, Mette Pøhl3, Anna Mann Nielsen2, Gitte Persson4,5
1Copenhagen University Hospital - Herlev-Gentofte, Department of Oncology, Copenhagen, Denmark; 2Copenhagen University Hospital - Herlev and Gentofte, Department of Oncology, Copenhagen, Denmark; 3Copenhagen University Hospital - Rigshospitalet, Department of Oncology, Copenhagen, Denmark; 4Copenhagen University, Department of Clinical Medicine, Copenhagen, Denmark; 5Copenhagen University Hospital- Herlev and Gentofte, Department of Oncology, Copenhagen, Denmark
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Purpose or Objective
A third of patients with non-small cell lung cancer (NSCLC) develop
brain metastases (BM). The prognosis for this patient group is historically
poor. National guidelines recommend whole brain irradiation (WBI) in case of
> 5 BM. However, for patients with a short life expectancy it is important
to consider treatment with supportive care alone.
The introduction of immune check point inhibitors (CPI) and targeted
therapies have increased life expectancies for the majority of patients with
NSCLC, but it is unknown if this is the case after WBI. This benchmarking study
examines overall survival after WBRT in a real-world cohort of patients with
NSCLC with focus on identifying subgroups of patients who do not benefit from
WBRT.
Material and Methods
Patients who received WBRT from July 2016 to June 2019, at two oncology
departments were included for analysis. Patients ID were retrieved from the
radiotherapy treatment planning system. Clinical information was retrieved from
electronic patient charts. Overall survival was measured from start of WBRT and
estimated using Kaplan-Meier. The following variables were included in a Cox proportional
hazards regression model to identify prognostic variables: Age, gender,
performance status, histopathological subtype including PD-L1 status.
Results
257 patients were included in the study. Median age was 66 years (range 40-94)
at time for WBRT. and 41.6% were men. A large majority (83.6%) had
adenocarcinoma, whereof 11.3% had EGFR or ALK mutations, 6.2% had squamous cell
carcinoma and 3.9% had NSCLC not otherwise specified (NOS). PD-L1 expression
was > 50% in 20,6%, 1-50% in 16.7%, <1% in 36.2% and unknown in 26.1% of
patients. WHO performance status where PS0 in 15.6%, PS1 in 25.9%, PS2 in 31.9%
and PS3 in 6.6%.
Median overall survival was 107 days (95% CI 90-124). Median survival
according to PS group 0-3 was 383 days (148-612), 153 (110-196), 62 (37-87) and
50 (17-83), respectively. Overall survival rates at 6 months and 1 year were 33.5%
(SD +/-3) and 19.1% (SD +/-2), respectively.
In Cox regression analysis, age (hazard ratio (HR) 1.02, 95% CI
1.00-1.03) and PS (HR 2.1; 1.77-2.52) were significant predictors of survival.
Additional adjustment for histopathological status and PDL1 receptor status did
not change the association.
Conclusion
Median overall survival after WBRT was more than 3 months but was
markedly lower in PS 2 and 3. Age and PS was significant predictors of
survival, with no significant impact of histopathology or PDL1 receptor status.