Patients were categorized into the mEHT group (62 patients, 51.7%) and the non-mEHT group (58 patients, 48.3%) according to whether or not mEHT was added.
During the radiotherapy period of approximately 4-6weeks, 5-fluorouracil (5-FU) or capecitabine was administered concurrently as a chemotherapeutic agent. 5-FU with leucovorin was injected as an intravenous bolus for 3 days in the first and last weeks of radiotherapy. Capecitabine was administered orally twice daily during radiotherapy. The mEHT was added during the radiotherapy period twice a week. Most patients (59 patients, 95.2%) in the mEHT group had more than 8 sessions and the mean mEHT total energy was 3769.9 KJ. Approximately 6-8 weeks after the completion of radiotherapy, surgery was performed.
mEHT was performed using a 13.56-MHz capacitive-coupled device (EHY-2000 Plus, Oncotherm GmbH). A 30 cm diameter-sized electrode was attached to the front of the body with a supine position adjusted to be located in the middle of the clinical target volume. Each mEHT session time was 60 minute and the time interval with radiotherapy was within one hour. On the first day of mEHT, the power of mEHT was set at 100W for the first 20 minutes, 120W for the next 20 minutes, and 140W for the last 20 minutes, if no toxicities were observed. From the subsequent treatment session, 140W was used.
The ypN positive rate was 19.3% (12 patients) in the mEHT group and 29.3% (17 patients) of the non-mEHT group. Downstaging was observed in 80.7% of patients in the mEHT group and in 67.2% of patients in the non-mEHT group. The tumor regression grade (TRG) was not significantly different between both groups. A good TRG score was significantly more frequent in the mEHT group (6 patients, 31.6%) than in the non-mEHT group (0 patients) for primary tumor volumes larger than 65mL.
ToxicityThere were 2 patients with the grade 3 mEHT-related toxicity, one with hot spots and the other with suspected fat necrosis, whose mEHT was discontinued. One patient had the mEHT only 3 sessions due to personal economic reasons. The incidence of leukopenia, neutropenia, and genitourinary toxicities were similar between the two groups. The proportion of gastrointestinal toxicity occurrence was 64.5% (40 patients) of the mEHT group, and 87.9% (51 patients) in the non-mEHT group.
Survival analysis was performed on 113 of 120 patients, except those who were lost to follow-up after surgery. The median follow-up period was 45 months (range, 7–71 months) in the mEHT group and 58 months (range, 6–95 months) in the non-mEHT group.
The 2-year OS was 100% in the mEHT group, not significantly different from 96% in the non-mEHT group. The 2-year DFS showed a difference between 96% in the mEHT group and 76% in the non- mEHT group.
The 2-year locoregional recurrence-free survival (LRRFS) was 98% for the mEHT group and 94%, for the non-mEHT group and the 2-year distant metastasis-free survival (DMFS) was 94% for mEHT group and 79% in non-mEHT group.
The overall mEHT group had a comparable response and survival using less radiation dosing compared with standard care; the subgroup with large tumors showed improved efficacy for tumor regression after mEHT.
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Scientific article publishing date : 2/8/2021
Immucura identifier :BSC21_078EN