ESTRO 2024 - Abstract Book

S1547

Clinical - Lower GI

ESTRO 2024

Results:

Forty-four pts with 67 lesions were treated with SABR. Median age of pts was 44 years (29-83). Primary tumor was: 1 anal cancer, 6 gynecological cancer, 2 biliary tract cancer, 6 colorectal cancer, 1 melanoma, 4 esophageal and gastric cancer, 5 breast cancer, 8 pancreatic cancer, 7 lung cancer, 1 prostate cancer, 1 thymus, 2 bladder cancer. Twelve pts were previously treated: 6 with surgery, 3 RF, and 3 with SABR. Thirty-one pts received chemotherapy (ChT): 15 pts 1 line, 10 pts 2 lines, 6 pts 3 or more lines. Seventeen pts continued systemic treatment during SABR (most of them with hormonal therapies). Twenty-eight lesions were treated with CK, the remaining 39 with HT. Median number of liver metastases/pt was 4 (1-6). Median GTV 43.78 cc (0.8 – 190.5) for CK and 41.99 cc (0.3 – 631.7) for HT. Median dose prescribed was 45 Gy (35-60) in 5 fractions (3-6), Median BED calculated with tumor specific a/b coefficient was 100 (59.5-378) Gy. Acute toxicities were G1 gastrointestinal. No cases of radiation induced liver disease (RILD) were registered. Two pts treated in the liver dome had late lung fibrosis. At a median follow of 14 months (0.5-81.5), 1 case of LR with CK and 11 cases with HT were observed. Six and 12-months Local Relapse Free Survival (LRFS) was 100% and 93.7% with CK, and 72.2%, and 69% with HT, respectively (P=0.03). No statistically significant difference was observed in OS between pts treated with HT and CK; it was 76.7%, 53.3%, and 41.1% at 6-, 12-, and 24-months, respectively.

Conclusion:

SABR for liver metastases is effective and well tolerated. A better local control was obtained due to the higher precision of CK vs HT, without an impact on OS because of distant metastases. Larger cohorts and longer follow up are needed to confirm these results.

Keywords: Liver Metastases, Stereotactic radiotherapy

2581

Poster Discussion

PET/MR imaging biomarkers of radioresistance in anal cancer patients

Tiril Hillestad 1 , Ragnhild Wisted 2 , Eirik Malinen 2 , Marianne Guren 3 , Tord Hompland 2

1 Oslo University Hospital, Department of Core Facilities, Oslo, Norway. 2 Oslo University Hospital, Department of Radiation Biology, Oslo, Norway. 3 Oslo University Hospital, Department of Oncology, Oslo, Norway

Purpose/Objective:

Anal cancer is a rear disease, but with increasing incidence. Treatment consists of fractionated chemo/radiation therapy and the 3-year progression-free survival is about 70%. Tumour radiosensitivity influence treatment response, and a more individually tailored treatment could increase the response rate and possibly also alleviate side effects. To achieve a more personalized treatment there is a need for a biomarker to select patients eligible for treatment modulation prior to, or early into the radiation treatment regime. Medical imaging such as MR and PET can provide important insight into the tumour microenvironment, essential for tumour radioresistance, and is already part of routine clinical practise.