Normal lung sparing Tomotherapy technique in stage III lung cancer

Chae-Seon Hong,Kwanghyun Jo,Dongryul Oh,Yong Chan Ahn,Hongryull Pyo,Sang Gyu Ju,Jae Myoung Noh,Kwangzoo Chung,Gyu Sang Yoo

doi:10.1186/s13014-017-0905-x

Chae-Seon Hong, Kwanghyun Jo + Show 7 more

Open Access

https://doi.org/10.1186/s13014-017-0905-x

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Abstract

PurposeRadiation pneumonitis (RP) has been a challenging obstacle in treating stage III lung cancer patients. Beam angle optimization (BAO) technique for Tomotherapy was developed to reduce the normal lung dose for stage III non-small cell lung cancer (NSCLC). Comparative analyses on plan quality by 3 different Intensity-modulated radiation therapy (IMRT) methods with BAO were done.Materials and methodsTen consecutive stage IIIB NSCLC patients receiving linac-based static IMRT (L-IMRT) with total 66 Gy in 33 fractions to the PTV were selected. Two additional Tomotherapy-based IMRT plans (helical beam (TH-IMRT) and static beam (TD-IMRT)) were generated on each patient. To reduce the normal lung dose, Beam angles were optimized by using complete and directional block functions in Tomotherapy based on knowledge based statistical analysis. Plan quality was compared with target coverage, normal organ sparing capability, and normal tissue complication probability (NTCP). Actual beam delivery times and risk of RP related with planning target volume (PTV) were also evaluated.ResultsThe best PTV coverage measured by conformity index and homogeneity index was achievable by TH-IMRT (0.82 and 1.06), followed by TD-IMRT (0.81 and 1.07) and L-IMRT (0.75 and 1.08). Mean lung dose was the lowest in TH-IMRT plan followed by TD-IMRT and L-IMRT, all of which were ≤20 Gy. TH-IMRT plan could significantly lower the lung volumes receiving low to medium dose levels: V5~30 when compared to L-IMRT plan; and V5~20 when compared to TD-IMRT plan, respectively. TD-IMRT plan was significantly better than L-IMRT with respects to V20 and V30 and there was no significant difference with respect to V40 among three plans. The NTCP of the lung was the lowest in TH-IMRT plan, followed by TD-IMRT and L-IMRT (6.42% vs. 6.53% vs. 8.11%). Beam delivery time was the shortest in TD-IMRT plan followed by L-IMRT. As PTV length increased, NTCP and Mean lung dose proportionally increased significantly in all three plans.ConclusionAdvantageous profiles by TH-IMRT could be achieved by BAO by complete and directional block functions. Current observation could help radiation oncologists to make wise selection of IMRT method for stage IIIB NSCLC.

Highlights

Over one-third of non-small cell lung cancer (NSCLC) patients are diagnosed at stage III
TH-Intensitymodulated radiation therapy (RT) (IMRT) plan could significantly lower the lung volumes receiving low to medium dose levels: volume receiving 5 Gy (V5)~30 when compared to linac-based static IMRT (L-IMRT) plan; and V5~20 when compared to TD-IMRT plan, respectively
TD-IMRT plan was significantly better than L-IMRT with respects to V20 and V30 and there was no significant difference with respect to volume receiving 40 Gy (V40) among three plans

Summary

Introduction

Over one-third of non-small cell lung cancer (NSCLC) patients are diagnosed at stage III. These have usually been the ideal candidates for high dose radiation therapy (RT) with concurrent chemotherapy [1,2,3,4,5,6,7]. Intensitymodulated RT (IMRT), through the inverse planning technique, can provide better target coverage and more sparing of the surrounding normal organs. IMRT has resulted in better clinical outcomes than 3D-CRT in treating stage III NSCLC patients, by dose escalation with more favorably limited V20 constraint [11,12,13,14]. While excellent dosimetric benefits have been noted with TH-IMRT for various disease sites, [21,22,23] it has not been widely investigated or accepted for the treatment of stage III NSCLC [24, 25]

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