Assessment of combined modality therapy for non-small-cell lung carcinoma: A simulation study concerning concurrent chemo-brachytherapy

Although surgery is the treatment of choice for early-stage non-small-cell lung carcinoma, almost two-thirds of patients do not have acceptable pulmonary function for extensive surgeries. The alternative approach for this large group of patients is sublobar resection along with low-dose-rate (LDR) brachytherapy (BT). However, patients with resected lungs have a high risk of recurrence and are often treated with platinum-based (Pt-based) chemotherapy (CT). In this study, we aimed to evaluate the absorbed doses of lung and other thoracic organs, considering concurrent chemo-BT with LDR sources in two modalities: conventional vs. unconventional Pt-based CT. We used the MCNPX code for simulations and to obtain the lung absorbed dose, dose enhancement factor (DEF), and Pt threshold concentration for the abovementioned modalities. Our results indicate that DEF correlates directly with Pt concentration at prescription point and is inversely correlated with depth. Dose enhancement for conventional CT concurrent with BT is < 2%, while it is > 2% in case of unconventional Pt-based CT wherein the Pt concentration exceeds 0.2 mg/g lung tissue. Also, the absorbed dose of healthy thoracic organs decreased by 2-11% in the latter approach. In conclusion, the concurrent chemo-BT in the lung environment could enhance the therapeutic doses merely by using unconventional CT methods, while lung Pt accumulation exceeds 0.2 mg/g.