Gastrointestinal Cancer

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SU_17_2170 - Stereotactic Body Radiation Therapy Post Induction Chemotherapy in Borderline Resectable and Locally Advanced Pancreatic Adenocarcinoma

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

Stereotactic Body Radiation Therapy Post Induction Chemotherapy in Borderline Resectable and Locally Advanced Pancreatic Adenocarcinoma
R. Engineer1, S. C. Lewis2, V. Ostwal1, A. Ramaswamy1, M. Bhandare1, V. Chaudhari1, Y. Ghadi1, M. B. Patil3, S. Gudi1, S. Sastri (Chopra)4, and S. Shrikhande1; 1Tata Memorial Centre, Mumbai, India, 2Tata memorial hospital, Mumbai, India, 3Tata Memorial Hospital, Mumbai, India, 4Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India

Purpose/Objective(s): To assess radiological response of the primary tumor to Stereotactic Body Radiotherapy (SBRT) post induction chemotherapy (ICT), acute toxicities and clinical outcomes.

Materials/Methods: Patients staged as BRPC (Borderline resectable Pancreatic cancers) or LAPC (Locally advanced Pancreatic cancers) between March 2016 to September 2017 treated with SBRT were included. All received 3-6 cycles of ICT using either mFOLFIRINOX (5-fluorouracil infusion (no bolus), irinotecan, oxaliplatin) or Nanoparticle albumin-bound paclitaxel (nab-P) plus gemcitabine (Gem) regimen at the discretion of medical oncologist. (SBRT) was planned after ICT using radiotherapy doses of 42 Gy/ 6# and 36Gy/6# over the period of 10 days. Patients not suitable for SBRT received hypofractionated schedule 39 Gy/13# with intensity modulated radiotherapy technique using image guidance. Triphasic contrast enhanced computed tomography CECT was done 6-8 weeks after SBRT for response assessment and decision regarding resectability. Patient continued to receive chemotherapy while waiting for surgery. Inoperable patients received further chemotherapy. Data was obtained from institutional electronic medical record.

Results: In the entire cohort of 35 patients, 11 patients were BRPC and 24 patients were LAPC. The Median follow up was 8 months (Range 4- 20 months). Nineteen (54%) patients received SBRT to a dose of 42 Gy/6#, 6 (17%) patients received 36Gy/6# and 10 (29%) patients were treated with 39Gy/13#. Respiratory motion management was done in 17 (49%) patients using deep inspiration breath hold technique. Radiological response was assessed at 6-8 weeks post radiotherapy and is summarized in Table 1. Radiological response was better in patients treated with mFOLFIRINOX than nab-P/Gem (PR 56% Vs 33 % p_0.06), receiving higher doses of RT (42 Gy/6# than 36Gy/6#, PR 56% Vs 33 % p_.71) though statistically not significant. 17 (48.5%) patients achieved radiological downsizing, of these 2 BRPC and 1 LAPC patient underwent resection (2 patients pT1N0 and 1 patient pT3 N0), 6 patients are planned for surgery and waiting for same, 3 patients showed distant metastasis (2 liver and 1 skin) at surgical evaluation 2 died of medical complications (1 cholangitis, 1 cardiac cause) and in 3 the tumor was still encasing the coeliac trunk. Updated results will be presented at the meeting. There was no ≥ 2 radiation related toxicity.

Conclusion: SBRT post ICT can achieve considerable radiological downstaging with acceptable toxicity and clinical outcomes. Factors affecting primary tumor response
Partial response (n=17) Stable disease (n =16) Local progression n=2 Total p
n(%) n(%) n(%)
BRPC LAPC 7(64) 10(42) 4(36) 10(42) 0 2(16) 11 24 0.42
Chemotherapy regimen
FOLFIRINOX GEM-NAB 10(71) 7(33) 3(22) 13(62) 1(7) 1(5) 14 21 0.06
RT doses
39Gy/13# 36Gy/6# 42Gy/6 5(56) 2(33) 10(56) 4(44) 4(67) 6(33) 0 0 2(11) 9 6 18 0.71

Author Disclosure: R. Engineer: None. S.C. Lewis: None. V. Ostwal: None. A. Ramaswamy: None. Y. Ghadi: None. S. Gudi: None. S. Sastri (Chopra): None. S. Shrikhande: None.

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