Esophageal gel-shifting technique facilitating eradicative boost or reirradiation to upper mediastinal targets of recurrent nerve lymph node without damaging esophagus
A 54-year-old male patient was referred for radiotherapy for a sole left RNLN metastasis. He had been diagnosed 1 year earlier with stage II, pT2N0M0 intrathoracic esophageal squamous cell cancer. He underwent thoracoscopic esophageal resection with lymph node dissection up to the second region, laparoscopic gastric tube creation and esophagogastric anastomosis in the posterior mediastinum followed by two cycles of chemotherapy, each consisting of 750 mg/m2 5-fluorouracil on Days 1–5 and 80 mg/m2 cisplatin on Day 1 (FP) []. He developed sepsis with Pseudomonas fluorescens, Clostridium glabrata, Acinetobacter baumannii and Staphylococcus epidermis, which was treated with antibiotics (ciproxan 400 mg/day and micafungin 100 mg/day for 4 weeks). One month prior to referral, follow-up CT revealed a RNLN recurrence that was treated with 50 Gy of external beam radiotherapy delivered in 2-Gy fractions for 5 weeks (Fig. A) and concomitant administration of one course of FP chemotherapy. However, fluoro-deoxy-glucose (FDG) positron emission tomography (PET) with X-ray CT study imaging 1 month after EBRT revealed persistent high FDG accumulation in the tumor (Fig. B). The patient desired boost treatment as soon as possible, and boost brachytherapy assisted by esophageal shifting was considered.\nAfter injection of the prepared gel, pooling of the gel and its shifting effect were confirmed on CT (Fig. A, B). We prescribed 20.0 Gy in one fraction (50.0 GyELQ2, α/β=10) to 90% of the PTV (Figs C, A), with D2cc of the shifted esophagus of 4.0 Gy (5.6 GyELQ2, α/β=3) (Fig. B). In a simulation without gel shifting, D2cc of the esophagus was calculated to be 7.3 Gy (15.0 GyELQ2, α/β=3). The enhancement factor due to gel shifting was 2.69 (15.0/5.6) for D2cc and 2.69 (24.4/9.07) for D1cc. The previous dose to the involved esophagus for the D2cc area was 20 Gy. (The area involved for D2cc was estimated at the time of brachytherapy planning after gel injection. The previously irradiated dose was not identical to the previously prescribed dose to the original target.) Thus, the accumulated esophageal D2cc and D1cc values were 65.0 Gy and 74.4 Gy without gel shifting, which decreased to 55.6 Gy and 59.1 Gy, respectively, with gel injection.