Potential benefits and pitfalls of respiratory-gated radiotherapy in the treatment of thoracic malignancy

Despite advances in radiotherapy delivery, the prognosis of lung cancer remains poor. Higher doses of radiation have been associated with improved outcomes but may result in higher toxicities. Respiratory gated radiotherapy (RGRT) has the potential to reduce pulmonary toxicity but there are significant limitations and pitfalls to its use. The aim of this article is to (i) describe the RGRT technique currently employed at Nepean and Westmead Hospitals; (ii) discuss the practical issues of implementing such a program; (iii) present the results of our RGRT program and (iv) review the potential uncertainties in using this technique and the methods we have used to overcome these.A retrospective review of all patients who had a 4D-computed tomography (4D-CT) scan was undertaken. Records from treatment planning systems were used to assess the prospective gating program.Between September 2007 and June 2011, 53 patients at Nepean and 26 patients at Westmead Hospital underwent a 4D-CT. Between April and August 2011, 26 patients at Westmead Hospital underwent a prospective 4D-CT scan as treatment verification. Two of the 26 patients (7.7%) were found to have incomplete coverage of the planning target volume. Both patients underwent respiratory re-coaching, alleviating the need for replanning.RGRT may reduce doses to organs at risk with the potential for dose escalation. However its implementation requires significant staff training, treatment time and resources. Treatment verification with image guided radiation therapy are essential for safe delivery.