[Target volume concepts in radiotherapy and their implications for imaging]

The Effect of Thoracic Radiotherapy on the Quality of Life in Lung Cancer Patients

Introduction

This study aimed to investigate changes in respiratory symptoms and quality of life (QoL) in patients with locally advanced and metastatic lung cancer receiving thoracic radiotherapy (RT). We investigated the correlation between the level of symptom relief and tumor response.

Methods

Thirty-two patients were included in this study. The European Organization for Research and Treatment of Cancer (EORTC) Quality of Life (QoL) Questionnaire (QLQ)-C30 and EORTC QLQ-LC13 were used to investigate QoL changes. Assessments were performed on the first day of RT, on the last day of RT, routinely monthly follow-ups, and three months after RT.

Results

The median age of the patients was 62; 88% of the patients were male. For the symptom scale, fatigue and dyspnea provided significant improvement at the end of RT (p=0.000, p=0.047). No significant improvement was observed at the end of RT in pain and insomnia. While coughing showed substantial improvement at the end of RT (p=0.004), the maximum improvement was achieved during the third-month follow-up (p<0.001). No significant improvement was observed at the end of RT in hemoptysis, but a considerable improvement was observed during the third-month follow-up (p=0.008).

Conclusion

This study confirms that RT offered palliation of respiratory symptoms and improved QoL in a substantial proportion of patients with lung cancer.

MR-guided radiotherapy of moving targets

INTRODUCTION

Hybrid magnetic resonance (MR) linear accelerators (MR-Linacs) for radiotherapy allow for the visualization and tracking of moving target volumes during the entire treatment. This makes gated treatments possible, decreasing the irradiated volumes and thus sparing healthy tissue from unnecessary radiation dose. Conventionally, tumors that are subject to respiration motion are treated by irradiating the entire area of potential target presence (internal target volume, ITV). This study presents three patient cases (lung, adrenal gland, and liver tumors) treated with gated MR-guided radiotherapy and compares the treatment plans retrospectively with conventional ITV plans.

MATERIALS AND METHODS

The gross tumor volume was delineated on MR and computed tomography (CT) images of the patients, and MR-Linac treatment plans were generated using additional clinical and planning target volume margins. The motion of the gross tumor volume was evaluated on two-dimensional cine-MRI images during the entire MR-Linac treatment. Based on the motion analysis, standard ITV-based plans were retrospectively created and compared by means of irradiated target volumes and dose-volume parameters.

RESULTS

For the MR-Linac plans, the irradiated treatment volumes were reduced by an average of 62% across the three cases, and for one case the ITV-based target volume would have overlapped with a critical organ. Target volume coverage was much better and the lung and adrenal MR-Linac plans revealed superior sparing of the organs at risks thanks to gated treatments.

CONCLUSION

Dosimetrically beneficial treatment plans with promising clinical outcomes can be applied when using gated MR-guided radiotherapy. Future studies will reveal which patients will benefit most from this technique. To utilize the full potential of online adaptive, individualized MR-guided therapy, the close collaboration of radio-oncology and radiology is needed.

Precision Radiotherapy: 18F-FDG PET-based radiotherapy planning in Head and Neck cancers

Precision medicine is gaining importance in this era of molecular imaging where the molecular features of a disease can be noninvasively assessed and treated with personalized medicine. This is especially suited for head and neck cancers (HNCa). Early stage HNCa are ideally managed with radiotherapy (RT) or surgery. Head and neck (HN) is a complex region and its tumors respond to RT differently due to dissimilar structures and moving organs such as tongue. Radiation oncologists are always in the process of trying and investigating newer RT techniques in order to achieve precise and targetted therapy to tumour/s. One such innovation is Intensity modulated RT (IMRT) using 3 Dimensional conformal RT (3DCRT). This 3DCRT resizes the radiation beams to match the shape of the tumor. Such focused dose escalation may improve local control in HNCa. Image guided RT in conjunction with IMRT is the most advanced form of RT planning being used these days. Simulation computerized tomography (CT) images are usually incorporated into RT planning module. But limitations of CT such as poor soft tissue contrast than magnetic resonance imaging and inability to clearly define solid / cystic / necrotic areas and viable tumour exist. Functional imaging such as Positron Emission Tomography (PET) has established its superiority over CT in delineating the actual site and extent of HN tumors. A combination of IMRT with BTV (Biological Tumour Volume) may be the most ideal technique to deliver a homogeneous radiation boost to tumour. This review shall discuss PET based RT planning, challenges, practical tips, and how to optimize therapy with the least side effects to the normal surrounding tissues.