Abstract 2234: Circulating tumor cells are rare in patients with curable oligometastatic cancer

Background: In the majority of patients with solid organ malignancies, tumor metastasis marks a transition from curable to terminal. However, a subset of metastatic cancer patients develops only a very limited number of metastases (known as oligometastatic). Survival in this cohort is considerably better than patients with widely disseminated cancer. In fact, in highly select subgroups, as many as 30% of oligometastatic patients are actually cured of cancer. The mechanism that distinguishes limited (or oligometastatic) cancer, from the more lethal, widely disseminated, is unknown. Tumor cell circulation is a critical component of metastasis formation, with circulating tumor cells being detectable in as many as 40-70% of patients with metastatic cancer. We hypothesize that patients with limited metastasis formation, have limited tumor cell circulation. To test this hypothesis, we quantified circulating tumor cells in patients with oligometastatic disease. Methods: Circulating tumor cells (CTCs) were quantified in patients with metastatic epithelial malignancies using the Veridex assay. Patients with > 2 CTCs in a 7.5 ml specimen were considered positive, as a single CTC has previously been shown to carry a substantially higher false positive rate (6.4%) than >2 CTCs (.3%). Results: From April 2008 to December 2009, a total of 20 patients with oligometastatic cancer were enrolled. In all patients the primary tumor had been previously removed and each was being evaluated for curative surgery to remove the oligometastatic cancer. The origin of the primary tumor was colon (17 patients), head and neck (1 patient), ovarian (1 patient), and pancreas (1 patient). The site of oligometastatic cancer was the liver (12 patients), lungs (4 patients) or both liver and lungs (4 patients). Only 1 of the 20 patients with oligometastatic cancer (5%) was found to have >2 circulating tumor cells. During the same time frame, CTCs were more common in patients with disseminated cancer as 4 of 7 patients (57%) with incurable, widely disseminated metastatic cancer had > 2 CTCs (two tailed P value = .0089). Conclusions: Circulating tumor cells are rare in patients with oligometastatic cancer. One mechanism by which oligometastatic cancer patients avoid more widely disseminated cancer may relate to the frequency and duration of tumor cell circulation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2234.