Rare Tumor Clinic: The University of California San Diego Moores Cancer Center Experience with a Precision Therapy Approach

BACKGROUND. Patients with rare tumors may lack approved treatments and clinical trial access. Although each rare tumor is uncommon, cumulatively they account for approximately 25% of cancers. We recently initiated a Rare Tumor Clinic that emphasized a precision medicine strategy. MATERIALS AND METHODS. We investigated the first 40 patients presenting at the Rare Tumor Clinic. Next‐generation sequencing (NGS) of tissue and plasma‐derived, circulating‐tumor DNA (ctDNA), and protein markers were assessed. RESULTS. Median age was 58 years (range, 31–78 years); 70% (28/40) were women; median number of previous systemic therapies was 2 (range 0–7). The most common diagnoses were sarcoma (n = 7) for solid tumors and Erdheim‐Chester disease (n = 5) for hematologic malignancies. Twenty distinct diagnoses were seen. Examples of ultrarare tumors included ameloblastoma, yolk sac liver tumor, ampullary cancer, and Castleman's disease. Altogether, 32 of 33 patients (97%) with tissue NGS and 15 of 33 (45%) with ctDNA sequencing harbored ≥1 alteration. Overall, 92.5% of patients (37/40) had ≥1 actionable target based on either genomic (n = 32) or protein (n = 27) markers. In total, 52.5% (21/40) received matched therapy; 52.4% (11/21) achieved stable disease (SD) ≥6 months (n = 3), partial remission (PR; n = 6), or complete remission (CR; n = 2). Matched therapy resulted in significantly longer progression‐free survival compared with last prior unmatched therapy (hazard ratio 0.26, 95% confidence interval 0.10–0.71, p = .008). CONCLUSION. Identifying genomic and protein markers in patients with rare/ultrarare tumors was feasible. When therapies were matched, >50% of patients attained SD ≥6 months, PR, or CR. Further precision medicine clinical investigations focusing on rare and ultrarare tumors are urgently needed. IMPLICATIONS FOR PRACTICE. Although rare tumors are infrequent by definition, when all subtypes of rare cancers are combined, they account for approximately 25% of adult malignancies. However, patients with rare tumors may lack approved treatments and clinical trial access. This paper describes an institutional a Rare Tumor Clinic focused on a precision medicine strategy. Performing genomics and protein analyses was feasible amongst patients with rare cancers. Over 50% of patients attained SD ≥6 months, PR, or CR when they received matched therapy (genomically targeted and/or immunotherapy). Further studies investigating the efficacy of the precision therapy approach among rare tumors are warranted.