Prognostic impact of solid tumor component diameter in early-stage non-small cell lung carcinoma treated with intensity-modulated fractionated radiotherapy: a retrospective analysis impact of solid tumor component diameter in NSCLC treated with IMRT.

Tomohiro Itonaga,Ryuji Mikami,Sachika Shiraishi,Tatsuhiko Saito,Kazuhiro Saito,Shinji Sugahara,Koichi Tokuuye,Mitsuru Okubo

doi:10.1259/bjr.20191027

Tomohiro Itonaga, Ryuji Mikami + Show 6 more

Open Access

https://doi.org/10.1259/bjr.20191027

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Abstract

Objective:To investigate the suitability of the new diameter-based subgroupings of the eighth edition Tumor Node Metastasis (TNM) classification system regarding radiotherapy treatment for early-stage non-small-cell lung cancer (NSCLC), we retrospectively re-analyzed the clinical data of patients treated with intensity-modulated radiotherapy using non-coplanar beams (ncIMRT) for Stage I NSCLC.Methods:Between March 2011 and March 2018, 92 patients with 94 tumors who were diagnosed with Stage I NSCLC according to the seventh edition TNM classification system were enrolled and underwent ncIMRT of 75 Gy in 30 fractions. Local control (LC), progression-free survival (PFS), and overall survival (OS) were retrospectively investigated according to the T-classification subdivisions of the eighth edition and maximal solid tumor component diameter.Results:The median follow-up period was 32.5 months. The median maximum tumor and solid tumor component diameters were 22 mm and 18 mm, respectively. 3-year LC, PFS, and OS rates were 84.1%, 69.4%, and 85.3%, respectively. The 3-year LC rates were 91.0 and 76.8% in the groups with tumor diameter ≤2 cm and >2 cm, corresponding to the T1c and T1b subdivisions of the eighth edition, respectively (p = 0.24). In the ≤2 cm and >2 cm solid tumor component groups, the 3 year LC rates were 93.6 and 63.2%, respectively, which were significantly different (p = 0.007).Conclusion:LC rates after radiotherapy in patients with Stage I NSCLC were correlated with solid tumor component diameter. High LC rates in patients with solid tumor components <2 cm in diameter were associated with high PFS and OS rates.Advances in knowledge:This study suggests that the eighth edition TNM classification system, which focuses on solid tumor components rather than tumor diameter, can be applied to radiotherapy.

Highlights

Because metastases to mediastinal and hilar lymph nodes are uncommon in early-stage non-small cell lung cancer (NSCLC), high dose concentration in the primary lesion may increase chances for a complete cure.[1]
As many patients had chronic pulmonary diseases in our studies, we reduced the fraction dose to minimize treatment- related toxicities: Non-coplanar intensity-m odulated radiotherapy with 75 Gy in daily doses of 2.5 Gy, which corresponds to 93.8 Gy in biologically effective dose calculation when α/β value was assumed to be 10, was used
The eligibility criteria were as previously reported[8 ]; briefly: (1) age of 20 years or older, (2) performance status of 0 or 1 according to the World Health Organization guidelines, (3) diagnosed with NSCLC by cytology or histology, or clinically diagnosed with NSCLC by findings on positron emission tomography (PET-CT) or a tumor that had increased by more than 25% within 2 months on CT when a histological diagnosis was not made, (4) clinical stage of T1-2 aN0M0 according to the seventh UIBC Tumor Node Metastasis (TNM) classification by CT or PET-CT taken within the past 40 days, (5) medically inoperable conditions determined by the cancer board, which consisted of thoracic surgeons, medical oncologists, radiation oncologists, and diagnostic radiologists

Summary

Introduction

Because metastases to mediastinal and hilar lymph nodes are uncommon in early-stage non-small cell lung cancer (NSCLC), high dose concentration in the primary lesion may increase chances for a complete cure.[1] For inoperable Stage I NSCLC, the sophisticated method of stereotactic body radiotherapy has shown higher local control (LC) and lower toxicity rates compared to those of conventional radiation therapies.[2,3,4,5,6] large tumors still recurred, even after high dose radiation therapy. The eighth edition of the Tumor Node Metastasis (TNM) staging system for NSCLC was released by the International Association for the Study of Lung Cancer (IASLC)[7] based on 70,967 patients with NSCLC between 1999 and 2010. In the eighth edition system, the T-c lassification was subdivided by 1 cm increments of the maximal tumor diameter

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