METHODS
Eighty patients who were diagnosed as having locally advanced NSCLC were selected from among patients
in whom PD-L1 status was assessed in the Gazi University pathology laboratory. The relationship
between PD-L1 and progression-free survival (PFS), OS, metastasis-free survival (MFS), RT response,
and RT doses was evaluated using Kaplan-Meier and Cox regression analysis. Chi-square and t-tests
were used for descriptive statistics.
RESULTS
The median follow-up was 16.1 months. The mean age was 61.1 years. PD-L1 positivity was detected in
34 patients. One year and 2-year OS and PFS ratios were found as 87%, 54% and 65%, 30%, respectively.
The median OS and PFS were 26.8 and 15.1 months, respectively. There was no statistically significant
difference between PD-L1 receptor status and OS and PFS (p=0.736 and p=0.372, respectively). In the
PD-L1 positive subgroup analysis for OS, doses higher than 60 Gy (n=28, mean dose 64.6±1.53) were
found superior to the 60 Gy dose (n=6) (p=0.034). The median MFS was 33 months.
CONCLUSION
PD-L1 status did not seem to be a predictor for RT response. However, despite the low number of
patients in the 60 Gy group, our study showed that dose-escalation could improve survival in PD-L1
positive locally advanced NSCLC.
Keywords: NSCLC; PD-L1; RT
The standard approach for Stage 3 NSCLC contains
multimodality therapy with combinations of systemic
therapy including chemotherapy and immunotherapy,
radiotherapy (RT), and surgery. However, the
selection of proper tools based on disease characteristics
is still argued. Despite significant debate about the
standard treatment for Stage 3 NSCLC (especially for
Stages 3A and 3B), definitive concurrent chemoradiation
is preferred for a substantial portion of patients
according to the size, the location and extension of
primary disease, lymph node involvement, low-performance
status, and surgical resectability of tumors.
Furthermore, as a result of recent Phase 3 studies,
durvalumab was added to standard care for Stage 3
NSCLC in consolidation therapy.[
Programmed death-ligand (PD-L1) receptors are
found on the surface of membranes of tumor cells and
are members of the B7 protein family.[
Due to the promising outcomes with PD-L1 inhibitors
in locally advanced and metastatic lung cancer
because of the synergistic interaction between RT and immunotherapeutics, great interest was directed
toward this topic. Therefore, the effects of RT on PDL1
receptors have been intensely investigated in the
literature. However, the predictive value of PD-L1 status
for RT response is still unknown. In this regard,
we aimed to investigate this relationship in our study.
Computed tomography (CTsim) (1 mm slices) was
performed for all patients before RT planning. Positron
emission tomography (PET/CT) images were fused
with CTsim for determining the gross tumor target
volume (GTV). GTV was contoured on both PET/CT
and CTsim images and summed. FDG-positive lymph
nodes on PET images and nodes larger than 1 cm were
also contoured as GTV. An additional 5-8 mm margin
was added to the GTV for the clinical target volume
(CTV). Planning target volumes (PTV) were defined
with 1-1.5 cm expansion from the CTV for three-dimensional
conformal RT plans. Internal target volumes
include all CTV positions during the breathing cycle
used for image-guided RT plans.[
RT started simultaneously with chemotherapy regimens.
However, 2-4 cycles of chemotherapy were administered
before RT for patients with bulky disease to
minimize the RT field and complications. Paclitaxel 45-
50 mg/m2 weekly and carboplatin area under the curve (AUC) 2 were administrated with concurrent RT. The
paclitaxel dose was upregulated to 200 mg/m2 every 21
days and carboplatin AUC 6 for an additional two cycles.
The doses of cisplatin were 50 mg/m2 on days 1, 8, 29,
and 36 and etoposide was 50 mg/m2 days 1-5 and 29-33.
RECIST criteria version 1.1 were used for evaluating
the RT response. In terms of RECIST criteria,
complete response requires the disappearance of all
target and non-target lesions and a short axis of all
lymph nodes smaller than 1 cm; partial response (PR)
requires a >30% decrease in the sum of the longest diameters
of the target lesions compared with baseline; stable disease requires neither PR nor progressive disease
(PD); PD requires >20% increase in the sum of
the longest diameter of target lesions compared with
the smallest sum recorded, or the appearance of one or
more new lesions, or unequivocal progression of nontarget
lesions, and at least 5 mm absolute increase of
target lesions.[
Ethical approval for the study was given by Gazi
University Clinical Researches Ethics Committee on
February 17, 2021.
The descriptive statistics for PD-L1-positive and
negative groups and comparisons between them are
shown in Table
PD-L1 status, age, sex, histology, stage of disease, recurrence,
distant metastasis, RT dose, chemotherapy timing,
tumor size, and treatment response were analyzed
for survival using the log-rank test (p=0.736, p=0.353,
p=0.922, p=0.372, p=0.458, p=0.36, p=0.075, p=0.359,
p=0.525, p=0.167, and p=0.036, respectively). Only the
complete response showed a statistically significant survival
advantage (p=0.036) (Table
PD-L1: Programmed death-ligand.
When PD-L1 positive subgroup analysis was performed,
doses higher than 60 Gy (n=28) were found
superior to the 60 Gy dose group (n=6) according to
the OS (p=0.034) (Fig.
PD-L1: Programmed death-ligand; RT: Radiotherapy; OS:
Overall survival.
Similarly, when PD-L1 negative subgroup analysis was performed, only the stage of disease presented as statistically significant for OS (p=0.035). Histology, RT dose, recurrence, and distant metastasis were not significantly associated with OS (p=0.528, p=0.369, p=0.805, and p=0.127, respectively).
PFS analysis was performed using the log-rank test
for different variables. PD-L1 status, age, histology,
T stage, RT dose, and tumor size were found not significant
for PFS (p=0.372, p=0.091, p=0.77, p=0.993,
p=0.945, and p=0.456, respectively). N stage, clinical
stage, and treatment response showed statistical significance
for PFS (p=0.017, p=0.023, and p<0.001,
respectively) (Table
PD-L1: Programmed death-ligand.
When PD-L1-positive subgroup analysis was performed, the PD-L1 expression percentage was seen to be associated with PFS (p=0.024). The median PFS for the <1% PD-L1 expression group was 8.4 months, 1-50% was 18 months, and >50% was 30.7 months.
PD-L1 status, histology, and clinical stage were found
associated with MFS in the log-rank test (p=0.015,
p=0.002, and p=0.039, respectively) (Table
PD-L1: Programmed death-ligand;.
Cross-tabulations were used to analyze the relationship between the PD-L1 status and local recurrence; treatment response and PD-L1 status; PD-L1 expression rate and treatment response; and PD-L1 expression rate and local recurrence. None were statistically significant (p=0.602, p=0.4, p=0.468, and p=0.404, respectively).
PD-L1 is the escape pathway of tumors from the
immune system of the body. Concordant with this, preclinical
evidence indicated poor prognosis with PD-L1
positivity.[
Most patients (91%) in our study received carboplatin+
paclitaxel chemotherapy. Therefore, the effect
of chemotherapy was neglected while evaluating PDL1
status and the RT response relationship. Steuer et
al.[
Doses higher than 60 Gy were found superior to
60 Gy doses for OS in the PD-L1-positive subgroup
analysis. These data contradict a landmark study of the
RTOG for RT doses in lung cancer. The RTOG-0617
study showed no survival advantage for dose escalation
up to 74 Gy in Stage 3 NSCLC.[
Dose escalation is a well-studied topic in locally
advanced NSCLC. Prolongation of overall treatment
time may cause increased repopulation and inferior outcomes. Furthermore, the escalated dose may contribute
to more severe complications and deteriorate
the patient"s general status.[
The primary endpoint of our study was to evaluate
the predictive value of RT for the treatment response
according to the PD-L1 status. Therefore, patients
treated with similar chemotherapy regimens were
selected to better distinguish the effect of RT for the
treatment response. However, our study has main limitations
such as the heterogeneity of the groups, and the
insufficient total number of patients for survival analyses
caused by the retrospective nature of our investigation.
Nevertheless, we believe that some of our research
data may guide further prospective studies.
Peer-review: Externally peer-reviewed.
Conflict of Interest: All authors declared no conflict of interest.
Ethics Committee Approval: The study was approved by the Gazi University Clinical Research Ethics Committee (No: 131, Date: 17/02/2021).
Financial Support: None declared.
Authorship contributions: Concept - V.D., M.A., F.D.; Design - V.D., M.A., F.D.; Supervision - M.A., F.D., N.A.; Funding - V.D., M.A., F.D., N.A.; Materials - E.A., Ç.G., E.Ş.; Data collection and/or processing - E.A., Ç.G., E.Ş., F.Ö., N.E.A., V.D.; Data analysis and/or interpretation - E.A., Ç.G., E.Ş., F.Ö., N.E.A., V.D.; Literature search - E.A., Ç.G., E.Ş., F.Ö., N.E.A., V.D.; Writing ? V.D., M.A.; Critical review ? M.A., F.D., N.A.