title: Incidental mediastinal dose does not explain low mediastinal node recurrence rates in patients with early-stage NSCLC treated with stereotactic body radiotherapy.
abstract: BACKGROUND
  Patients with stage I non-small-cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT) do not undergo a staging mediastinoscopy, yet reported mediastinal recurrence rates appear lower than in patients undergoing surgical resection. We determined incidental SBRT doses to assess whether this could account for the low rates of recurrence.
  
  
  METHODS
  Between March 2009 and September 2012, we reviewed cases of patients with inoperable lung tumors (n = 136) treated with SBRT at our institution. The SBRT regimen was 54 Gy in 3 fractions with positron emission tomography/computed tomography (PET/CT) staging. Incidental doses to the mediastinal lymph node stations (MLNSs), primary tumor control, locoregional (LR), distant control (DC), and overall survival (OS) rates were determined.
  
  
  RESULTS
  Forty-six patients with stage I NSCLC met the inclusion criteria. The calculated median incidental SBRT dose to all MLNSs was < 5 Gy for the majority of patients (75%). At a median follow-up of 16.8 months (0.6-38.9 months), the 1- and 2-year primary tumor control, LR, OS, and DC rates were 100% and 95.5%, 97.4% and 81.7%, 88.1% and 81%, and 96.9% and 86.9%, respectively. Only 2 patients (4.9%) had mediastinal recurrence, with incidental SBRT doses to MLNSs that were similar to the rest of patients (P > .05).
  
  
  CONCLUSIONS
  Low mediastinal recurrence rates in stage I NSCLC treated with SBRT validates the omission of staging mediastinoscopy. The low incidental dose to MLNSs does not seem to explain the low mediastinal recurrence in the majority of patients. Our findings also confirm that prophylactic radiation to the mediastinum is not necessary and support the hypothesis that local ablation of the primary lesion could indirectly affect subclinical nodal disease through unknown mechanisms.
authors.affiliation: Department of Radiation Oncology, Ronald Reagan UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Jean-Claude M
authors.initials: JC
authors.lastname: Rwigema
authors.affiliation: Department of Radiation Oncology, Ronald Reagan UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Allen M
authors.initials: AM
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, Ronald Reagan UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Pin-Chieh
authors.initials: PC
authors.lastname: Wang
authors.affiliation: Division of Thoracic Surgery, Ronald Reagan UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Jay M
authors.initials: JM
authors.lastname: Lee
authors.affiliation: Department of Medical Oncology, Ronald Reagan UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA.
authors.forename: Edward
authors.initials: E
authors.lastname: Garon
authors.affiliation: Department of Radiation Oncology, Ronald Reagan UCLA Medical Center, David Geffen School of Medicine at UCLA, Los Angeles, CA. Electronic address: percylee@mednet.ucla.edu.
authors.forename: Percy
authors.initials: P
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000628:therapy; D008198:Lymph Nodes / Q000473:pathology* / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D011379:Prognosis; D011829:Radiation Dosage; D016634:Radiosurgery
keywords: Mediastinal recurrence; Mediastinoscopy; Non–small-cell lung cancer; PET/CT staging; Stereotactic body radiotherapy