It has been estimated that 76% of patients with lung cancer should receive radiotherapy as part of their treatment. Some recent developments include:
Target definition. FDG PET scanning has revolutionised our ability to stage lung cancer accurately, and to discriminate active cancer from benign changes, such as atelectasis.
Image guided radiotherapy (IGRT). Lung tumours move during and between treatments. It is possible to measure intrafraction motion due to ventilation using 4D CT. Changes in tumour location between treatments can be identified using cone beam CT immediately before treatment delivery. This is important in the delivery of precision techniques such as stereotactic ablative body radiotherapy (SABR) for stage I lung cancer.
Adaptive radiotherapy (ART). Changes in tumour size identified on CT over a course of radiotherapy may allow for adjustment in field size, with sparing of normal tissues. Using the novel PET tracer FLT, we have identified changes in tumour proliferation during treatment, to which treatment can be adapted.
Enhancing radiation response. The addition of systemic platinum based chemotherapy to radical radiotherapy has improved survival in patients with locally advanced disease. Although there are good theoretical reasons for combining some targeted agents with radiotherapy, e.g. EGFR inhibitors, a beneficial effect is yet to be shown. PET scanning has revealed some lung cancers to be hypoxic, a potential cause of radioresistance, but also a possible target for emerging hypoxic cell sensitizers.
Are we making progress? In stage I non-small cell lung cancer, hypofractionated SABR achieves local control in 90%, comparable with surgery. For locally advanced disease, the survival at five years following conventional radiotherapy in the 1980’s was 5%; now it is in the region of 30%. Further progress is likely with a better understanding of the molecular and microenvironmental causes of radiation resistance; these may be susceptible to novel targeted radio-enhancing pharmaceuticals.