Elsevier

Lung Cancer

Volume 82, Issue 2, November 2013, Pages 260-265
Lung Cancer

Stereotactic body radiotherapy for lung tumors in patients with subclinical interstitial lung disease: The potential risk of extensive radiation pneumonitis

https://doi.org/10.1016/j.lungcan.2013.08.024Get rights and content

Abstract

Purpose

To evaluate the toxicity and efficacy of thoracic stereotactic body radiotherapy (SBRT) in patients with subclinical interstitial lung disease (ILD).

Methods and materials

One hundred patients with 124 lung tumors were treated with SBRT at our institution according to our own protocols; patients with subclinical (untreated and oxygen-free) ILD were treated with SBRT, while those with clinical ILD (post- or under treatment) were not. The administration of 48 Gy in four fractions was used in 103 (83%) of the 124 tumors. The presence of subclinical ILD in the pre-SBRT CT findings was reviewed by two chest radiologists. The relationships between radiation pneumonitis (RP) and clinical factors were investigated.

Results

Subclinical ILD was recognized in 16 (16%) of 100 patients. Grade 2–5 RP was recognized in 13 (13%) of 100 patients. Grade 2–5 RP was observed in three (19%) of 16 patients with subclinical ILD. Subclinical ILD was not found to be a significant factor influencing Grade 2–5 RP; however, extensive RP beyond the irradiated field, including the contralateral lung, was recognized in only three patients with subclinical ILD, and the rate of extensive RP was significantly high in the patients with subclinical ILD. Grade 4 or 5 extensive RP was recognized in only two patients with subclinical ILD. Dosimetric factors of the lungs (V5, V10, V15, V20, V25, MLD) were significantly associated with Grade 2–5 RP. The three-year overall survival and local control rates of all patients were 53% and 86%, respectively. No significant differences were seen in either overall survival or local control rates between the patients with ILD and those without ILD.

Conclusions

Subclinical ILD was not found to be a significant factor for Grade 2–5 RP or clinical outcomes in the current study; however, uncommon extensive RP can occur in patients with subclinical ILD.

Introduction

Stereotactic body radiotherapy (SBRT) has become widespread as a new treatment modality for pulmonary lesions in recent years due to its high local control rate and completely painless and ambulatory treatment. Although adverse reactions are not recognized in most patients treated with SBRT, radiation pneumonitis (RP) is an occasional complication of SBRT. Previous reports have shown a correlation between severe RP and dose–volume parameters, such as the mean lung dose (MLD), V20 (percentage of the lung volume receiving > 20 Gy) and V5 [1], [2].

A group of noninfectious, acute and chronic diffuse parenchymal lung disorders are classified as interstitial lung disease (ILD). More than 150 clinical conditions and/or causes are associated with ILD [3]. The COPD Gene Study group previously demonstrated both chest computed tomographic (CT) and pathologic evidence of subclinical ILD in asymptomatic members; 194 (8%) of 2416 screening HRCT scans in a cohort of smokers showed interstitial lung abnormalities [4]. The frequency of acute exacerbation following conventional radiotherapy in patients with ILD has been reported to be around 25% [5], [6]. The eligibility criteria for patients in a phase I/II study of SBRT to treat primary lung cancer showed that active ILD is a factor for patient exclusion [7]. The clinical guidelines for SBRT published by the Japanese Society for Therapeutic Radiology and Oncology also recommend that SBRT should be relatively contraindicated in patients with severe ILD.

Beginning in August 2005, at our institution, the use of SBRT to treat patients with stage I non-small cell lung cancer (NSCLC) or metastatic lung tumors was initiated according to our own protocols. Patients with subclinical (untreated and oxygen-free) ILD were treated with SBRT, while those with clinical ILD were not. To our knowledge, there are only a few case series evaluating SBRT in patients with subclinical ILD [8], [9], [10]. The purpose of our study was to evaluate the toxicity and efficacy of thoracic SBRT in patients with subclinical ILD and to investigate whether subclinical ILD is a predictor of RP.

Section snippets

Patients

Between August 2005 and February 2011, SBRT was performed to treat lung tumors at our institution in 109 consecutive patients with 138 lung tumors. For this study, we retrospectively collected data for patients who received follow-up for a minimum of six months. Nine patients who were followed up for less than six months were excluded. One hundred patients with 124 lung tumors were included in this study. According to our own protocols for SBRT, during the same period, patients with subclinical

Results

The median follow-up period after SBRT was 17.1 months (range, 6.0–71.5 months). Subclinical ILD on the pre-SBRT CT findings was recognized in 16 (16%) of 100 patients: 84 patients with no evidence of ILD (score 0), two patient with a status of slight ILD (score 1), five patients with a status of mild ILD (score 2) and nine patients with moderate ILD (score 3).

Grade 2 or higher RP was recognized in 13 (13%) of 100 patients: Grade 5 in one patient, Grade 4 in one patient, Grade 3 in four

Discussion

Promising clinical results of thoracic SBRT with high local control rates and the absence of severe toxicities have been demonstrated [7], [15]. Recently, thoracic SBRT has been performed as a standard treatment method in patients with medically inoperative NSCLC or those who refuse surgery, especially to treat peripheral lesions. Previous studies of thoracic SBRT have reported a 9–28% incidence of Grade 2 or higher RP [2], [16], [17], [18], [19]. To our knowledge, however, only a few papers

Conflict of interest statement

Potential conflicts of interest do not exist in this study.

References (27)

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