In a new study recently published in SpringerPlus, a team of researchers from Japan developed a 6-field technique using lateral beams in conformal radiotherapy and evaluated this method in lung cancer patients who have bilateral supraclavicular lymph node metastasis.
The prevailing standard of care for patients with locally advanced lung cancer is concurrent chemoradiotherapy. The method of three-dimensional conformal radiotherapy (3D-CRT), is able to obtain a conformal dose distribution to the target volume, while reducing the dose administered to normal tissue is reduced.
Using oblique beams has been found to reduce the dose of radiation delivered to the spinal cord, off-cord. However, in patients with bilateral supraclavicular lymph node metastases, it is not possible to use simple fields when delivering off-cord oblique beams. Normally each side the supraclavicular lymph node is irradiated independently after the first field irradiation, using anterior-posterior opposite beams. However, the conformity of the dose distribution is not satisfactory when simple anterior-posterior opposed beams are used.
In order to improve the conformity, in the study entitled “Lung cancer: a 6-field technique using lateral beams in conformal radiotherapy for bilateral supraclavicular lymph node metastases”, Dr. Shinichi Tsutsumi from Osaka City University Graduate School of Medicine, and colleagues developed a 6-field technique using lateral beams.
All six fields had the same isocenter point (IP). Two fields using anterior-posterior opposed beams involved all of the planning target volume (PTV). The next 2 fields using off-cord oblique beams involved the PTV inferior to the IP. The remaining 2 fields using lateral opposed beams, that shielded the spinal cord, involved the PTV superior to the IP.
The team evaluated this technique in a sample of 6 patients with bilateral supraclavicular lymph node metastases. From these, 4 patients suffered from non-small-cell lung cancer and 2 had small-cell lung cancer, with definitive radiation therapy using previous planning.
The researchers found this method was applicable in the 4 patients with NSCLC. However, in the 2 patients with SCLC, the cumulative volume of lung which received a radiation higher than 20 Gy surpassed 37% of the lung volume.
The team concluded that the 6-field technique using lateral beams was efficient in 67% of the patients with lung cancer who had bilateral supraclavicular lymph node metastasis. However, in the remaining 33% patients this method was not contraindicated. Further studies are necessary to evaluate this technique in larger samples.