Bone marrow-sparing intensity-modulated radiation therapy for Stage I seminoma

A direct association between radiotherapy dose, side-effects and secondary cancers has been described in patients with seminoma. A treatment planning study was performed in order to compare computed tomography-based traditional radiotherapy (CT-tRT) versus bone marrow-sparing intensity-modulated radiation therapy (BMS-IMRT) in patients with Stage I seminoma.

We optimized in 10 patients a CT-tRT and a BMS-IMRT treatment plan to deliver 20 Gy to the para-aortic nodes. CT-tRT and IMRT consisted of anteroposterior-posterioranterior parallel-opposed and seven non-opposed coplanar fields using 16 and 6-MV photon energies, respectively. Dose-Volume Histograms for clinical target volume (CTV), planning target volume (PTV) and organs at risk (OARs) were compared for both techniques using Wilcoxon matched-pair signed rank-test.

D(mean) to CTV and PTV were similar for both techniques, even if CT-tRT showed a slightly improved target coverage in terms of PTV-D(95%) (19.7 vs. 19.5 Gy, p = 0.005) and PTV-V(95%) (100 vs. 99.7%, p = 0.011) compared to BMS-IMRT. BMS-IMRT resulted in a significant reduction (5.2 Gy, p = 0.005) in the D(mean) to the active bone marrow (ABM). The V(100%) and V(75%) of the OARs were reduced with BMS-IMRT by: ABM-V(100%) = 51.7% and ABM-V(75%) = 42.3%; bowel-V(100%) = 15.7% and bowel-V(75%) = 16.8%; stomach-V(100%) = 22% and stomach-V(75%) = 27.7%; pancreas-V(100%) = 37.1% and pancreas-V(75%) = 35.9% (p = 0.005 for all variables).

BMS-IMRT reduces markedly the dose to the OARs compared to CT-tRT. This should translate into a reduction in acute and long-term toxicity, as well as into the risk of secondary solid and hematological cancers.