To explore the feasibility and efficacy of a dose intensification with Intensity Modulated Radiation Therapy and Simultaneous Integrated Boost (IMRT-SIB) in locally advanced esophageal and gastroesophageal cancer (GEJ). We retrospectively analyzed a series of 69 patients with esophageal or GEJ cancer treated at our Institute, between 2016 and 2019, with preoperative IMRT and SIB up to 52.5-54 Gy in 25 fractions in 5 weeks and concurrent carboplatin (AUC2) and paclitaxel (50 mg/m ), as in the CROSS regimen. All patients completed the planned IMRT-SIB program with a median of four (range 1-5) cycles of concurrent paclitaxel/carboplatin. Compliance to IMRT-SIB was 93%, whereas 54% of patients received four to five cycles and 87% at least three cycles of concurrent carboplatin/paclitaxel. Grade 3 toxicity was reported in 19% of patients. Complete clinical response (cCR) was achieved in 48%, and 13% had disease progression after chemoradiation (CRT). Overall, 49% of patients underwent surgery; reasons for non-operation included cCR in cervical tumor location (10%) or cCR and patient decision (13%). A pathologic complete response (pCR) was achieved in 44% of resected patients. Postoperative complications and mortality rates were 21 and 6%, respectively. At a median follow-up of 12 months (6-25), 2-year overall and progression-free (PFS) survival rates were 81 and 54%, respectively. No difference in PFS by histologic type in operated patients was reported. Non-operated cCR patients had higher PFS, including cervical locations and selected cCR patients who decided for non-operation (75 30%, p < 0.01). The study reported favorable results in safety and feasibility of the IMRT-SIB dose intensification in our preoperative CRT program. The toxicity was acceptable, allowing a high compliance to intensified radiation doses with dose reduction of concurrent paclitaxel/carboplatin in some patients. The high rate of cCR and pCR suggested this intensified program is effective in the preoperative CRT and, for selected responsive patients, in the non-operative approach to esophageal and GEJ cancer. The 2-year survival rates were promising. A prospective study is being planned to confirm these observations.