Treatment planning for dose escalation in non-small cell lung cancer (NSCLC)

This study was performed to examine potential field arrangements for irradiating non-small cell lung cancer (NSCLC) on a dose escalation study. An example patient was chosen and 7 coplanar treatment plans were created to treat a NSCLC. Two plans included prophylactic nodal irradiation (PNRT) and 5 did not. Four plans used 4 fields, 2 plans used 5 fields, and 1 plan included dynamic conformal 360 degrees rotational therapy. All plans delivered 80 Gy to the isocenter with 10-MV x-rays. Each plan was initially created without dose inhomogeneity corrections and then was recalculated with these corrections, maintaining the same weighting and number of monitor units. Avoiding PNRT spared a considerable volume of normal tissue from radiation. Plans with 5 fields generally spared normal tissues better than 4-field plans. There was no benefit to the dynamic conformal 360 degrees rotational plan. Inhomogeneity corrections revealed that higher doses were delivered to both the tumor and normal structures. Seven beam arrangements for the treatment of NSCLC were compared to develop potential beam arrangements that would be applicable to treating NSCLC on a multi-institutional dose escalation study. We favor the use of at least 5 beams in most situations. It is possible that the use of more fields would further improve plans up to a point of diminishing returns, as exemplified by the lack of benefit seen with the dynamic conformal 360 degrees rotational plan. It is possible that the use of noncoplanar fields or intensity-modulated radiation therapy (IMRT) may further improve the therapeutic ratio.