ASTRO 2015: Involved-Field Irradiation for Locally Advanced Esophageal Cancer Reduces Toxicity Without Increasing Locoregional Lymph Node Recurrence
For patients with locally advanced esophageal cancer that has spread to the lymph nodes, radiation therapy that targets only the involved lymph node regions results in less toxicity without causing a statistically significant difference in locoregional lymph node recurrence, distant failure, and overall survival rates, according to research presented by Li et al on October 19, 2015, at the American Society for Radiation Oncology’s (ASTRO’s) 57th Annual Meeting in San Antonio, Texas.
Chemoradiation is a standard treatment for locally advanced esophageal cancer. Elective nodal irradiation—radiation therapy to the tumor and lymph nodes, including uninvolved lymph nodes in the region around the cancerous tumor—is a common form of radiation therapy to treat esophageal cancer. However, the use of elective nodal irradiation has been controversial due to increased levels of irradiation and possible toxicity.
This study evaluated the feasibility of reducing the nodal irradiation volume of radiation therapy by comparing elective nodal irradiation to involved-field irradiation—radiation therapy that involves only the regions where the lymph nodes are located.
Study Details
The prospective, randomized controlled clinical trial included 110 patients with esophageal cancer enrolled from nine cancer centers across China between April 2012 and November 2014. The patients had inoperable, newly diagnosed stage II–III thoracic esophageal squamous cell carcinoma.
Patients were treated with concurrent chemoradiotherapy, and all of the patients received docetaxel (75 mg/m2 on day 1) and cisplatin (25 mg/m2 on days 1–3) every 21 days for two to four cycles. The patients received image-guided radiation therapy in once-daily fractions of 1.8–2 Gy to a total dose of 60–66 Gy to the gross tumor volume and 50–54 Gy to the clinical target volume.
Patients were randomly divided into two groups; 56 patients received elective nodal irradiation, and 54 patients received involved-field irradiation.
The primary endpoints of the study were toxicities and locoregional lymph node recurrence. The secondary endpoints were distant failure and overall survival.
Study Findings
At a median follow-up of 20 months, data showed that involved-field irradiation resulted in significantly decreased radiation pneumonitis and radiation esophagitis. The incidence of grade ≥ 2 radiation pneumonitis in the elective nodal irradiation group was 26.8%, compared to 12.9% in the involved-field irradiation group (P = .011), and the rate of radiation esophagitis was 37.5% in the elective nodal irradiation group compared to 20.4% in the involved-field irradiation group (P = .001).
No significant differences in the locoregional lymph node recurrence rate were observed between the two groups. The elective nodal irradiation group experienced a 17.9% locoregional lymph node recurrence, compared to the involved-field irradiation group, which experienced a 20.4% locoregional lymph node recurrence (P = .819).
Evaluation of distant failure rates indicated a positive result with no difference between the two groups. The elective nodal irradiation group had a 12.5% distant failure rate and the involved-field irradiation group had a 13% distant failure rate (P = .465).
The two groups achieved similar 1-year and 2-year overall survival rates. The 1-year overall survival rate was 89.2% for the elective nodal irradiation group and 88.3% for the involved-field irradiation group (P = .431), and the 2-year overall survival rates were 64.2% for the elective nodal irradiation group vs 55.6% for the involved-field irradiation group (P = .857).
“Elective nodal irradiation is the most commonly used type of radiation therapy for treating esophageal cancer, but its side effects and toxicity have been criticized,” said Tao Li, MD, PhD, Vice Chairman of the Department of Radiation Oncology at Sichuan Cancer Hospital and Institute. “Researchers have suggested decreasing the nodal irradiation volume with the use of involved-field irradiation, yet prior to this study, its potential advantages had only been measured in smaller trials.”
He continued, “We anticipated that involved-field irradiation could significantly decrease toxicity such as radiation pneumonitis and radiation esophagitis, but were initially uncertain if involved-field irradiation might increase the locoregional lymph nodal recurrence rates, distant failure, and overall survival. The midterm results of our trial show that involved-field irradiation is an acceptable and toxicity-minimizing method of treatment for thoracic esophageal squamous-cell carcinoma. This is a significant discovery for future esophageal cancer radiotherapy care.”
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