New era of lung cancer radiotherapy; from Stone Age to 2lst Century.

Radiotherapy (RT) remains an important curative therapy option for patients with localised and locally advanced non-small cell lung cancer (NSCLC); yet the survival results are disappointing. While this may be due to patient factors such as comorbidity and age, local tumour control is a determinant of survival and improvement in the technique of radiation delivery offers a real chance for significant improvement in disease control with potential impact on survival. The talk will focus on novel tech-niques of irradiation to optimise the target dose distribution and minimise the dose to normal lung and provide both predicted and actual clinical results.

Curative RT needs to be delivered to the whole tumour to an adequate dose. This requires accurate tumour delineation and delivery of tumoricidal dose to the whole tumour. Historically 2D and 3D radiotherapy may not have included the full excursion of the tumour motion during each fraction and between fractions and (equivalent path length) dose calculation algorithms not taking into account lateral transport, will have overestimated the dose to the target. 4D image acquisition and adaptive RT with image guidance (IGRT) ensure the whole of the tumour is treated throughout the course of radical RT and modern planning systems (using convolution superimposition or Monte Carlo based algorithms) give more accurate information on true dose distribution.

Introduction of novel technologies is based on the assumption of a dose response relationship for NSCLC and there is a substantial body of evidence to support this. The major challenge for RT of NSCLC is intrafraction and interfraction tumour motion. The potential solutions include conventional delivery with delineation of motion trajectory with 4D imaging, motion control breath-hold techniques to minimise the motion combined with gated treatment delivery and tracking techniques. We have demonstrated that the potential sparing of normal lung achieved with gated treatment during an imposed breath hold may allow for doubling of tumour control probability at two years using equitoxic dose escalation.

Modern imaging and IGRT to accurately delineate tumour before and during treatment and modern techniques of delivery with optimised dose distribution and dealing with tumour motion to minimise the dose to the lung, provide a real opportunity for improved tumour control. The apparent success of hypofractionated high precision radiotherapy (stereotactic body radiotherapy - SBRT) for small lung tumours in achieving good local disease control offers the opportunity to translate this approach to larger tumours using novel technologies. The potential benefit will need to be demonstrated in well-designed prospective dose escalation studies with survival as the principal endpoint of efficacy.