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- Published on: 4 March 2020
- Published on: 4 March 2020
- Published on: 4 March 2020Response to Kennedy et al
We thank Dr Kennedy and colleagues for their interest in our recent
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paper comparing outcomes after surgery and SABR radiotherapy in
stage I non-small cell lung cancer (1,2) .
We agree that intraoperative nodal upstaging can be a cause of stage
migration in the surgical arm but not the SABR arm, and so could act
as a potential bias in an observational study. This might
overestimate the benefit of surgery compared to SABR. The Society
for Cardiothoracic Surgery Database Project reported 2155 patients
undergoing lung cancer resections in England from 2014-16, and
found that over 13% of patients underwent nodal upstaging when
their resection pathology was analysed (3) .
The information bias inherent in having full pathological data
available for surgical but not SABR cases leads to other potential
problems with analysis. All patients undergoing surgery have a
pathological analysis confirming the cancer and its stage, while 240
of the 476 patients treated with SABR were treated without a
pathological diagnosis. A recent prospective UK study found that
14% of patients operated on for presumed lung cancer had benign
disease on intraoperative frozen section biopsy or final pathology (4) .
Assuming that this surgical false negative rate approximates the rate
in the suspected early clinical stage patients treated with SABR, then
around 7% of our SABR arm may...Conflict of Interest:
None declared. - Published on: 4 March 2020Nodal staging should not be left out of the equation
We read with interest the report from Khakwani and colleagues comparing real-world outcomes for patients with stage I NSCLC undergoing surgery and stereotactic radiotherapy (SABR) (Ref 1), together with the accompanying editorial (Ref 2). Given the failure to recruit to previous randomised trials designed to compare these treatments, analyses of large national datasets are vital to improve our understanding of how best to manage this patient group.
One additional possible explanation for the worse outcome in the SABR cohort relates to occult nodal involvement. Inaccuracies in clinical staging are well described; one analysis documented that 34% of patients are under-staged by pre-operative work-up (Ref 3). Patients with occult nodal disease would have been identified in the surgical group by intraoperative systematic nodal staging, and would therefore have been excluded from analysis of the Stage I cohort presented here (Ref 1). Patients who are similarly under-staged prior to SABR treatment will remain in the Stage I cohort for analysis, yet will have worse outcomes by virtue of their more advanced disease. Comparing outcomes on an intention-to-treat basis using pre-treatment stage may minimise this bias.
We agree with the authors that residual confounding may be an important factor explaining these results, and that examination of cause of death is instructive. In our single centre study, cause of death was compared (on an intention to treat basis) between...
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None declared.