Single Institutional Experience Using Radiation Therapy in the Treatment of Neuroendocrine Tumor Primary and Metastatic Lesions

Abstract

The role of radiation therapy (RT) in the treatment of patients with neuroendocrine tumors (NETs) has not been well established. We aim to report on our experience using RT as part of curative or palliative treatment in patients with NET. This was an IRB approved single-institutional retrospective cohort study including patients with NET who received curative- or palliative-intent RT from 2013-2022. Outcomes included cumulative incidence of local progression (LP) and overall survival (OS). Univariate and multivariate methods were used to assess disease and treatment characteristics associated with outcomes. RT dose was converted to biologically effective dose (BED10), assuming α/β = 10 Gy. Sixty-six patients who received treatment to 89 total lesions were included for analysis. The median age at RT was 56 years (range: 20-95). ECOG performance status was 0-1 in 49 and 56% were male. Primary tumor origin included: 28 pancreas, 12 lung, 8 small intestine, 5 colorectal, 2 stomach, and 11 unknown/other primary cancers. Tumor grade included 1 (62%), 2 (1%), 3 (17%) or unknown (18%). 20% were functional. 43% of patients had metastatic disease at diagnosis, 24 were initially M0 and developed M1 disease in their disease course, and 12 remained M0. RT was delivered to the primary tumor (59%) or metastatic sites (41%). Treatment was either curative-intent (37%), including "curative" intent oligometastasis direct therapy, or palliative-intent (63%). For the 27 patients with M1 disease at time of RT, 1 had all sites controlled by local therapies at the time of RT. The location of the treated lesions included 17 pancreas, 13 bone, 12 thorax, 4 colorectal, 3 small bowel, and 15 other. Median RT dose and number of fractions were 30 Gy (IQR: 20-45) and 5 (IQR: 5-15). The median BED10 was 48 (IQR: 28-65) for all lesions and 60 (IQR: 58-69) for lesions treated curatively. 21 (32%) patients received concurrent systemic therapy with RT. The median follow-up per patient and per lesion were 15 months (IQR: 6-33) and 13 months (IQR: 5-28). The median OS was 34.5 months (95% confidence interval [CI]: 16.6-NE). The 3-year cumulative incidence of local progression was 15% (95% CI: 8-28%). BED10 was not associated with LP. These data support the use of RT as a highly effective local treatment modality in the care of patients with either localized or metastatic NET.