IMRT Reduces Acute Toxicity in Patients Treated with Preoperative Chemoradiation for Gastric Cancer

Abstract

Two large randomized trials are currently investigating preoperative chemoradiation for localized gastric adenocarcinoma. However, radiation therapy (RT) can be associated with relatively high rates of acute toxicity. Newer techniques, such as intensity modulated RT (IMRT), could reduce toxicity by reducing radiation dose to normal structures. Our goal was to compare rates of toxicity, toxicity-related events, and oncologic outcomes in patients treated with IMRT compared to 3D conformal RT (3DCRT). The records of 202 gastric cancer patients treated with preoperative intent RT at our institution from 1998-2018 were retrospectively reviewed. Demographic data, treatment details, acute and late toxicities (CTCAE 4.0), progression and survival data were recorded. Patients who had stage IV disease were excluded. Statistical analysis included descriptive statistics, Cox regression analysis, and Kaplan-Meier survival. 54% were male, and the median age was 63. 82 patients received 3DCRT and 120 patients received IMRT. The median radiation dose was 45Gy (IQR: 45-45 Gy). 78% of patients in the 3DCRT group and 95% of patients in the IMRT group received neoadjuvant chemotherapy prior to RT (p=0.001). 99% of patients in both groups received concurrent chemotherapy. There were no significant differences between the 3DCRT and IMRT groups with respect to gender, race, histology, tumor, or nodal stage. The rate of grade 3-4 acute toxicity was significantly lower in patients treated with IMRT compared to those treated with 3DCRT (53% vs. 73%, p=0.004). The composite rate of toxicity-related events (hospitalization, feeding tube, IV rehydration or RT breaks) was also significantly lower in patients treated with IMRT compared to 3DCRT (56% vs. 85%, p<0.001). 73% of patients who received 3DCRT and 68% of patients who received IMRT underwent subsequent surgical resection (p=0.245). Among patients who underwent surgical resection, there was no significant difference in the rate of positive margins between those who received 3DCRT and those who received IMRT (7% vs 15%, p=0.13). Among patients who underwent surgical resection, the 3-year OS and PFS rates were not significantly different in patients receiving 3DCRT compared to IMRT (OS 73% vs. 73%, p=0.93, PFS 65% vs. 64%, p=0.68). Among patients who did not undergo surgical resection, the 3-year OS and PFS rates were also not significantly different in patients receiving 3DCRT compared to IMRT (OS 27% vs. 28%, p=0.93; PFS 19% vs. 14%, p=0.69). Our study indicates a reduction in the rates of grade 3-4 acute toxicity and toxicity-associated events in patients treated with IMRT compared to 3DCRT, with no significant difference in oncologic outcomes. These findings suggest that IMRT should be considered as the preferred radiation modality in patients treated with preoperative chemoradiation for gastric cancer.