Gastrointestinal Cancer

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SU_6_2059 - Acute Toxicities and Short-Term Follow-up of Patients Treated with Pencil-Beam Scanning Proton Beam Radiation Therapy for Esophageal Carcinoma: A Single-Center Experience

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Acute Toxicities and Short-Term Follow-up of Patients Treated with Pencil-Beam Scanning Proton Beam Radiation Therapy for Esophageal Carcinoma: A Single-Center Experience
R. S. Bhangoo1, N. Y. Yu1, J. B. Ashman1, H. Paripati2, C. E. Vargas1, H. Ross2, W. G. Rule3, and T. T. W. Sio1; 1Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 2Department of Hematology-Oncology, Mayo Clinic, Phoenix, AZ, 3Mayo Clinic, Phoenix, AZ

Purpose/Objective(s): Excess radiation dose to the heart and lungs may impact outcomes for patients (pts) with esophageal cancer (EC). Proton beam radiotherapy (PRT) has a distinct dosimetric advantage over photons in this patient population. However, limited data has been reported on side effects and clinical outcomes using pencil-beam scanning PRT. We analyzed the acute RT-related toxicities and short-term survival results in the initial cohort of EC pts treated at our institution with intensity modulated PRT.

Materials/Methods: After IRB approval, a single-institution retrospective review was conducted on all pts who underwent concurrent chemoradiation (CRT) using PRT for EC treatment with definitive or neoadjuvant intent from 2016 to 2017. Patient, treatment, toxicity and outcome characteristics were abstracted from electronic medical records. Frequency (%) for categorical variables and median values (interquartile range) for continuous variables were calculated. Outcomes (locoregional recurrence free survival [LRFS], distant metastasis-free survival [DMFS], and overall survival [OS] since diagnosis) were determined using Kaplan-Meier methods.

Results: Twenty-three (23) pts were included. Median follow-up of the patient cohort was 9.5 months (IQR 4.4-13.5). Median age was 72 (68-76) years. Seventeen (74%) were male. Nine (39%) had a feeding tube placed prior to RT. ECOG performance status was 0-1 in 22 (96%) pts. Tumor location was mid-esophagus in 4 (17%) and distal in 19 (83%) pts. 15 (65%) tumors were adenocarcinoma and 8 (35%) squamous cell carcinoma. Treatment intent of CRT was neoadjuvant in 19 (83%) and definitive in 4 (17%) cases. Twenty-two (96%) of pts received neoadjuvant chemotherapy with carboplatin/paclitaxel. The most common PRT regimen (19 [83%] pts) was 50 Gy (range 41.4 -56 Gy) in 25 fractions (range 23-28). A 45-Gy volume (along with 50 Gy) via simultaneous integrated boost was used in 18 (95%) of the pts. All 23 pts completed planned PRT with only 3 (13%) pts requiring a treatment break (all ≤ 2 weekdays). Treatment-related grade 3 toxicities included dysphagia (3 [13%] pts), nausea (1 [4%] pts), and anorexia (3 [13%] pts). An enteric feeding tube was placed during PRT in 2 (9%) pts. Esophageal stenosis was present in 3 (23%) of pts. One grade 4 toxicity was recorded for gastric perforation 2 months after RT which required urgent laparotomy and repair. At the time of this analysis, 10 (43%) pts have undergone surgical resection. Two (20%) pts achieved pathologic complete response and 6 (60%) other pts were down-staged. At one year, OS, LRFS, and DMFS rates of 79%, 74%, and 65% were achieved.

Conclusion: Due to the potential of decreasing cardiopulmonary symptoms, PRT is an attractive treatment modality for patients with EC. Although a small experience with short-term follow-up, our cohort showed promising outcomes and acute toxicity profiles in both definitive and neoadjuvant settings. Further investigation comparing proton to photon-based RT in larger patient cohorts is warranted.

Author Disclosure: R.S. Bhangoo: None. N.Y. Yu: None. J.B. Ashman: None. C.E. Vargas: Independent Contractor; Mayo Clinic. Stock; View Ray. Chairman; Proton Collaborative Group. W.G. Rule: None. T.T. Sio: None.

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