ESTRO 38 Abstract book

S871 ESTRO 38

response to palliative radiation therapy of painful bone metastases from solid malignant carcinomas. Material and Methods Consecutive patients with painful bone metastases treated with palliative radiation between 2013 and 2017 in our institution were enrolled. Patients without pain and those with vertebral bone metastases were excluded. The reason for excluding vertebral bone metastases was that it was usual to contour the whole body of metastatic vertebra as the clinical target volume (CTV), and, thus, the effect of how to contour GTV for vertebral bone metastases was thought to be much less than that for long or flat bone metastases. The imaging modality used between one month before and the start of palliative radiation, primary sight of carcinoma, histological type, metastatic lesion type (osteolytic, osteoblastic, or mixed) and the biological equivalent dose of α/β=10 (BED10) were retrospectively investigated, and the relationships between these factors and treatment response were evaluated. “Response” was defined as the condition in which patients achieved pain relief or reduced their use of analgesic medications. All radiation plans were three- dimensional conformal radiation therapy based on simulation CT images according to the guideline of the Japanese Society for Radiation Oncology. Briefly, GTV was defined as the bone metastatic lesion according to physical and any imaging examinations. CTV was defined as GTV plus about 1 cm, and planning target volume (PTV) was defined as CTV plus about 0.5-2 cm. Results Forty-three patients were included in the present study (median age 67 years; age range 37-85 years; 27 males, 16 females). Prescribed doses were 8-50 Gy/1-25 fractions with 2-8 Gy/fraction. Response was seen in 36 (response rate, 84%). The number of each imaging modality before irradiation was 43 CT scans (all patients, including simulation CT for radiation planning), 10 MRI scans, 17 bone scintigraphies, and 6 18 FDG-PET images. Welch’s t- test, Mann-Whitney test and the chi-squared test showed that only BED10 was significantly related to treatment response (p<.01) (Table 1), and multiple logistic regression analysis also showed that only BED10 was a significant predictor (p=.02) (Table 2). No significant relationship was observed with imaging modality before irradiation.

Conclusion The results of the present study suggest that appropriate radiation field setting according to CT images and physical assessment could avoid further imaging before palliative radiation for painful bone metastases. EP-1616 Population-based Phase II Trial of Stereotactic Radiotherapy for up to 5 Oligometastases: SABR-5 R. Olson 1 , M. Liu 2 , A. Bergman 3 , S. Lam 4 , F. Hsu 5 , B. Mou 6 , T. Berrang 7 , A. Mestrovic 8 , N. Chng 9 , D. Hyde 10 , Q. Matthews 9 , C. Lund 11 , D. Glick 7 , H. Pai 7 , P. Basran 8 , H. Carolan 2 , B. Valev 12 , S. Tyldesley 2 , D. Schellenberg 11 1 BC Cancer Agency - Centre for the North, Radiation Oncology, Prince George, Canada ; 2 BC Cancer, Radiation Oncology, Vancouver, Canada ; 3 BC Cancer, Medical Physics, Vancouver, Canada ; 4 BC Cancer, Clinical Trials, Vancouver, Canada ; 5 BC Cancer, Radiation Oncology, Abbotsford, Canada ; 6 BC Cancer, Radiation Oncology, Kelowna, Canada ; 7 BC Cancer, Radiation Oncology, Victoria, Canada ; 8 BC Cancer, Medical Physics, Victoria, Canada ; 9 BC Cancer, Medical Physics, Prince George, Canada ; 10 BC Cancer, Medical Physics, Kelowna, Canada ; 11 BC Cancer, Radiation Oncology, Surrey, Canada ; 12 BC Cancer, Radiation Oncology, Prince George, Canada Purpose or Objective Oligometastases refer to a state of disease where cancer has spread beyond the primary site, but is not yet widely metastatic, often defined as 1-3 or 1-5 metastases in number. Stereotactic ablative radiotherapy (SABR) is an emerging radiotherapy technique to treat oligometastases that require further prospective population-based toxicity estimates. Material and Methods This is a non-randomized phase II trial in a setting where SABR for oligometastases is not available off clinical trial. All participants receive SABR treatment to all sites of newly diagnosed or progressing oligometastatic disease. We have accrued 150 of a planned 200 patients to assess toxicity associated with this experimental treatment. The study was powered to give a 95% confidence on the risk of late grade 4 toxicity, anticipating a < 5% rate of grade 4 toxicity. Results We have accrued 150 patients within 18 months, and anticipate completion of study accrual by December 2018. The majority (65%) had a solitary metastasis, followed by 26%, 7%, and only 2% who had 2,3, or 4-5 metastases, respectively. Within the 150 patients, 220 metastases were treated, with the most common locations being lung (35%), non-spine bone (24%), spine (21%), lymph nodes (9%), and liver (7%). The majority of primary tumour sites were prostate (27%), colorectal (21%), breast (11%), renal cell carcinoma (11%), and head and neck cancer (9%). To date, no SABR related deaths have occurred, but there has been 1 grade 4 serious adverse event related to SABR reported (biliary duct stenosis resulting in jaundice). Updated adverse event rates will be presented. Conclusion SABR treatment of oligometastases is occurring off-trial at a high rate, without sufficient evidence of its efficacy or toxicity. We will present toxicity data from this population-based cohort, using standardized doses and organ at risk constraints. EP-1617 Palliative radiotherapy for lung cancer from patients’ perspective: a quality of life (QoL) study W. Majewski 1 , M. Wyduba 2 1 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Radiotherapy Department, Gliwice, Poland ; 2 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Anaestesiology Department, Gliwice, Poland