Does Imrt Offer Clinically Meaningful Advantages In The Adjuvant Management Of Gastric Cancer?

Although chemoradiation was viewed as the standard of care in the adjuvant management of gastric cancer since the publication of INT 0116, a more recent phase III trial (MAGIC) did not include radiotherapy in the randomization schema. The subtext of the latter trial (i.e., that radiation may be expendable in this disease) mandates that future prospective studies utilizing radiotherapy optimize its application. We therefore set out to determine whether IMRT could improve upon our published 3-D conformal approach for treatment to the stomach and draining nodes. A total of 10 patients with adenocarcinoma of the stomach were treated with adjuvant chemoradiotherapy using a non-coplanar four-field arrangement (Soyfer et al., IJROBP 2007;69:364-369). In each case, parallel planning using an IMRT approach was carried out for comparative purposes. Two beam arrangements were evaluated: Beam arrangement 1: gantry angles 0° 53° 107° 158° 204° 255° 306°. Beam arrangement 2: gantry angles 30° 90° 315° 345° and gantry angle 320°/couch 30° gantry angle 35°/couch 312°. The plans generated were subsequently assessed for target volume coverage and dose deposition in adjacent critical organs. Dose-volume histograms (DVHs) were generated for the CTV, kidneys, spine, and liver. The comparative study of the CTVs revealed satisfactory coverage by the 95% isodose envelope with either treatment approach (IMRT or 3D). The liver, spine and right kidney showed marginal benefit from the IMRT approach. In the left kidney, the mean dose dropped from 33 Gy in the conformal plan to 13 Gy in the IMRT plan. IMRT offers marginal benefits in the adjuvant treatment of gastric cancer and should only be offered to the small subset of patients with risk factors for kidney disease or pre-existing nephropathy.