Systematic EndoscopIc Staging of Mediastinum to determine Impact on radiotherapy for locally advanced lung Cancer (SEISMIC): interim results from a prospective multicentre interventional study.

D. Steinfort*^a (Dr), D. Ost^b (Prof), K. Yasufuku^c (Dr), J. Annema^d (Prof), L. Crombag^d (Dr), B. Jennings^e (Dr), D. Fielding^f (Dr), P. Nguyen^g (Dr), S. Yo^e (Dr), K. Rangamuwa^a (Dr), P. Lee^b (Dr), Y. Shi^h (Dr), J. Simpson^h (Prof), G. Kothariⁱ (Dr), N. Hardcastleⁱ (Dr), S. Sivaⁱ (Dr)

^a Royal Melbourne Hospital, Melbourne, AUSTRALIA ; ^b The University of Texas, MD Anderson Cancer Center, Houston, UNITED STATES ; ^c Toronto General Hospital, Toronto, CANADA ; ^d University of Amsterdam, Amsterdam, NETHERLANDS ; ^e Monash Health, Melbourne, AUSTRALIA ; ^f Royal Brisbane and Women's Hospital, Brisbane, AUSTRALIA ; ^g Royal Adelaide Hospital, Adelaide, AUSTRALIA ; ^h University of Melbourne, Melbourne, AUSTRALIA ; ⁱ Peter MacCallum Cancer Centre, Melbourne, AUSTRALIA

* Daniel.Steinfort@mh.org.au

Background

Curative-intent treatment of patients with Stage III non-small cell lung cancer (NSCLC) frequently includes radical radiation, with International guidelines recommending radiation fields be constructed based on PET-identified extent of disease. Selective (targeted) LN sampling is most commonly performed. Studies in early stage (Stage I-II) NSCLC confirm systematic mediastinal lymph node (LN) staging with endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) improves accuracy of mediastinal staging. We sought to determine the impact of systematic mediastinal LN staging in Stage III using EBUS-TBNA to accurately delineate disease extent.

Methods

Consecutive participants with Stage III NSCLC based on clinical imaging underwent systematic LN staging via EBUS-TBNA. (ACTRN12617000333314). Primary study outcome was proportion of patients with PET-occult LN metastases detected by EBUS.

Results

Data was available for 168 of 173 eligible patients at the time of writing. M:F 103:65. Mean age 68+/-9 years.

EBUS demonstrated findings concordant with PET-identified mediastinal LN involvement in 101 (58%) of patients, with discordant findings (primary outcome) observed in 67 (40%) of patients.

PET-occult disease was identified by EBUS in 18 (10.4%) patients, with 11 of these upstaged (9 patients N2 → N3). EBUS identified lesser extent of disease in 49 patients (29%) with 38 (23%) down-staged to N1 (11) and N0 (27). Surgical confirmation of results was performed in 18 of 38, with 100% concordance.

Conclusion

Systematic LN staging via EBUS-TBNA identifies PET-occult LN disease in 10.4% of patients. A significant proportion of patients with cN2/3 NSCLC are confirmed to have pN0/1 following systematic assessment of mediastinal LN.

Further analysis will identify risk factors for identification of PET-occult metastases, and will confirm the impact PET-EBUS discordance in Stage III NSCLC on radiation dosimetry and tumour control probability.

Disclosure of funding source(s): none