Gastrointestinal Cancer

MO 08 - GI 2 - Anorectal and Liver Cancers

1089 - Tumor Response After Preoperative Chemoradiation Therapy with Simultaneous Integrated Boost Using Volumetric Modulated Arc Therapy in Locally Advanced Rectal Cancer

Monday, September 16
11:00 AM - 11:05 AM
Location: Room W175

Tumor Response After Preoperative Chemoradiation Therapy with Simultaneous Integrated Boost Using Volumetric Modulated Arc Therapy in Locally Advanced Rectal Cancer
M. Adli1, H. Alkis1, B. Z. Gulegen1, S. Halil2, A. Dagli Degerli1, F. Ozturk1, V. Atalay3, and C. Yegen3; 1Department of Radiation Oncology, Marmara University School of Medicine, Istanbul, Turkey, 2Department of Medical Oncology, Marmara University School of Medicine, Istanbul, Turkey, 3Department of Surgery, Marmara University School of Medicine, Istanbul, Turkey

Purpose/Objective(s): To retrospectively investigate the efficacy of preoperative dose escalation using simultaneous integrated boost with volumetric modulated arc therapy (SIB-VMAT), concomitant with capecitabine chemotherapy, in locally advanced rectal cancer.

Materials/Methods: Between February 2015 and October 2018, 87 patients with stage II-III rectal adenocarcinoma received preoperative 50.4 Gy to the pelvic lymph nodes and simultaneously delivered 56 Gy to the tumor, in 28 fractions, using SIB-VMAT, concomitant with capecitabine, 825 mg/m2 bid. Tumor response rates were analyzed.

Results: Median age was 60 (18-85). Female/male ratio was 32/55. Tumor location was distal rectum in 32 (36.8%) patients, mid-rectum in 27 (31%), and proximal rectum in 28 (32.2%). All patients completed the treatment. Eighteen patients (20.7%) refused surgery or were medically inoperable. Sixty-nine patients underwent surgical resection. Median time to surgery from the completion of radiotherapy was 11 (6-55) weeks. Surgery was low anterior resection in 48 (69.6%) patients, abdomino-perineal resection in 19 (27.5%) and local excision in 2 (2.9%). Clinical (n=14) or pathological (n=12) complete response was achieved in 26 (29.9%) patients. Microscopic disease only (“a few tumor cells”) was reported in 7 (8%) patients and tumor size less 5 millimeters in 5 (5.7%). Resection margins were free in all operated patients. Sphincter preservation rate for the distal rectal tumors was 43.8%, including five patients with clinical complete response. Metastatic pelvic lymph nodes were reported in 15 of 67 (22.4%) patients with lymph node dissection. Except diarrhea in three (3.4%) patients, which resolved after capecitabine discontinued, there was not any Grade ≥3 acute toxicity. Erectile dysfunction (n=2) or delayed surgical wound healing (n=2) was reported in 4 (5%) patients after surgery.

Conclusion: Preoperative radiotherapy with dose escalation using SIB-VMAT is well tolerated, with a low toxicity profile, and can achieve a high rate of clinical/pathological complete or near-complete response and down-staging in locally advanced rectal cancer patients. Further studies with larger patient number and longer follow-ups are needed.

Author Disclosure: M. Adli: None. H. Alkis: None. B.Z. Gulegen: None. A. Dagli Degerli: None. F. Ozturk: None.

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