eP168 - Presacral Neuroendocrine Neoplasms: A Multi-site Review of Surgical Outcomes

Purpose/Background: Presacral neuroendocrine neoplasms (PNENs) are rare, and there is a lack of published data on management strategies and outcomes.Methods/Interventions: Data on all patients who underwent surgical treatment for PNEN between March 2006 and June 2023 were abstracted from electronic health records at two tertiary referral centers. Descriptive statistics were used to report the results, and a time-to-event Kaplan-Meier analysis was employed to describe recurrence rates.Results/Outcomes: Twelve patients were identified, 8 were female, with an average age of 44.8 ± 15.9 years. Back pain (50%), constipation (50%), and abdominal discomfort (41.7%) were the predominant symptoms preoperatively. Eleven had primary PNEN, and one was a local recurrence initially managed at another institution. Preoperative imaging included CT scan (16.7%), MRI and CT scan (75%), and MRI alone (8.3%). Somatostatin receptor imaging was obtained in 75% of patients. A preoperative biopsy was conducted in 83.3% of patients, which was diagnostic for a neuroendocrine neoplasm with the exception of one case. Fifty percent of patients had a metastatic disease at diagnosis. Surgical approaches included anterior (25%), posterior (58.3%), and combined approaches (16.7%). Levator muscles were transected in 33.3%, coccygectomy was required in 41.7%, and sacrectomy in 16.7%. Nine cases underwent en bloc excision, while in three cases, the cyst capsule was ruptured. An R0 resection was achieved for all patients. Estimated blood loss was 700 ± 784 ml, and average stay was 4.4 ± 1.9 days. Short-term complications affected 25% of patients. There were no operative mortalities. Most PNENs were well-differentiated (91.7%), grade 2 (83.3%), with mean Ki-67 of 5.9 ± 5.1%. Synaptophysin testing was positive in 83.3% of the cases, while chromogranin A was positive in 66.7%. Cystic components were present in 58.3%. Most PNENs were associated with congenital cysts (66.6%), the most common being the tail-gut cysts (41.7%); four tumors lacked associated lesions. Mean diameter was 6.3 ± 3.1 cm. Four (33.3%) patients received adjuvant therapy with somatostatin receptor antagonists. Four (33.3%) required additional intervention including cytoreductive surgery, peptide receptor radionuclide therapy, transarterial chemoembolization of liver metastases and systemic chemotherapy (with FOLFOX, CAPTEM and everolimus) due to disease progression. During the follow-up period, five patients developed skeletal metastases. The liver was the second most common site for distant metastases with three cases, followed by the thyroid with two cases. Lung metastases and pancreatic metastases occurred in one case each. The mean follow-up period was 72.7 ± 66.9 months. A 5-year local recurrence rate of 23.8% was observed with one recurrence in a patient diagnosed with metastatic disease at the outset (Figure 1). There was a 14.3% disease progression rate and a 30% de novo metastases rate (Figures 2 & 3). A 5-year disease-free survival of 40% was observed, with a 100% 5-year overall survival rate.Conclusion/

Discussion: This study represents a large surgical series of PNENs. Many patients will have metastatic disease at the time of diagnosis. Despite this, there was good overall survival following surgery and multi-modality treatment. Given the small number of patients in this study, and the rare nature of PNENs, a multi-center study is warranted."Figure 1

Local recurrence Kaplan Meier
Figure 2

Disease progression Kaplan Meier
Figure 3

De novo metastases Kaplan Meier"