ESTRO 2024 - Abstract Book

S2173

Clinical - Upper GI

ESTRO 2024

Purpose/Objective:

The primary purpose of palliative care is to improve symptom control and quality of life. There is limited evidence associating palliative care interventions with improved overall survival (OS) in cancer patients. We performed an international multicenter clinical trial to study the palliative efficacy of a new technique, single-fraction celiac plexus radiosurgery, in patients with severe retroperitoneal pain syndrome (NCT03323489). We have previously reported that 53.3% of evaluable patients had a positive pain response. Likewise, the intervention appeared to improve quality of life. Here, we perform a post-hoc analysis to test the hypothesis that a positive response to treatment would be associated with lengthened overall survival.

Material/Methods:

This is a post-hoc analysis of a prospective single-arm phase II clinical trial that accrued and treated 125 patients at eight medical centers across five continents. Inclusion criteria for the original trial included an average pain level of ≥ 5/11 (based upon the Brief Pain Inventory Short Form (BPI -SF) average pain score), ECOG 0- 2, life expectancy ≥ 8 weeks, and either pancreatic cancer or malignant anatomical involvement of the celiac blood vessels. A positive pain response (the primary endpoint) was defined as a ‘complete or partial pain response’ based upon the BPI -SF average pain 11- point scale: a decrease between the score immediately before treatment and 3 weeks’ post treatment ≥ 2 was considered meaningful. Protocol defined criteria for evaluability included being alive at three weeks post treatment, and having stable pain scores prior to treatment. OS was defined as the time from enrollment until death. The relationships between continuous and categorical covariates and overall survival (OS) were examined utilizing Cox-regression methodology, employing Stata/IC 16 (StataCorp, College Station, USA). A total of 90 evaluable patients were included in this analysis. Median age was 65.5 years (IQR 58.3-71.8), 65% were female, 92% had pancreatic cancer, and 86% had metastatic disease. Median ECOG was 1 (IQR 1-2). Patients were diagnosed with a median of 302 (IQR 134-522) days prior to enrolment. The median number of systemic treatment lines prior to enrolment was 1 (IQR 1-2), and the median baseline intravenous opioid equivalent dose was 31 mg/d (IQR 12.5-66.7). All patients were deceased at the time of analysis; none had been lost to follow-up. Median OS was 122 days (IQR: 77-190 days). On univariate analysis, the following were significantly associated with improved survival: Body mass index (BMI) HR 1.08 (CI 1.01-1.16) p=0.03 (low BMI better) and a positive pain response HR 0.63 (CI 0.41-0.97) p=0.04. There was no association with age, gender, marital status, tumor type, presence of metastases, performance status, baseline QOL, pain levels, morphine dose, irradiation of the primary tumor, or change in opioid dose. The median OS in responders was 144 days versus 100 days in non-responders. In a multivariate model incorporating just BMI and a positive pain response, both retained significance: BMI HR 1.10 (CI 1.02-1.18) p=0.01 and positive pain response HR 0.58 (CI 0.37-0.89) p=0.01. Results:

Conclusion:

Patients with a good palliative response to celiac plexus radiosurgery lived longer than those who did not respond, even when the tumor itself was not treated. The reasons underlying this finding, whether associative or causative, are worthy of further study.