Precision Medicine May Benefit Patients with Rare Tumors

Identifying genomic and protein markers in patients with rare/ultra-rare tumors appears to be feasible. In addition, more than half of patients with rare/ultra-rare tumors may achieve stable disease (SD) for 6 months or longer, a partial response (PR), or a complete response (CR), according to researchers at the University of California San Diego Moores Cancer Center. They report in The Oncologist that patients with rare tumors often lack approved treatments and clinical trial access.

Rare tumors are uncommon; however, cumulatively these cases account for approximately 25% of cancers. Consequently, the study researchers established a Rare Tumor Clinic that emphasizes a precision medicine strategy. They investigated the outcomes of the first 40 patients and assessed the patients based on next-generation sequencing (NGS) of tissue and plasma-derived circulating-tumor DNA (ctDNA). Protein markers were also examined.

The median age was 58 years (range, 31-78 years) and 70% of patients were women. Among the 40 patients studied, the median number of previous systemic therapies was 2 (range, 0-7). The most common diagnoses were sarcoma (n = 7) for solid tumors followed by Erdheim-Chester disease (n = 5) for hematologic malignancies. The clinicians were able to make 20 distinct diagnoses. Ultra-rare tumors included ameloblastoma, yolk sac liver tumor, ampullary cancer, and Castleman's disease.

The study showed that 97% of patients with tissue NGS and 45% with ctDNA sequencing harbored one or more identifiable alterations. In addition, 92.5% of patients had one or more actionable targets based on either genomic or protein markers.

The study showed that 52.5% received matched therapy; of these patients, 52.4% (11 patients) had good responses. Among the 11 patients, 3 achieved SD for 6 months or longer, 6 had a PR, and 2 had a CR. According to the authors, the matched targeted therapy approach also resulted in significantly longer progression-free survival (PFS) compared with the last prior unmatched therapy (hazard ratio, 0.26; 95% CI: 0.10-0.71; P = .008). They noted that no major side effects were identified and most patients suffered only minor side effects that were manageable.

Study investigator Shumei Kato, MD, a medical oncologist at the Center for Personalized Cancer Therapy and Division of Hematology and Oncology at the University of California San Diego Moores Cancer Center in La Jolla, California, said the strategy of matching patients with treatment based on specific biomarkers is ready for the clinic. However, he said it requires a multidisciplinary, supportive team infrastructure.

He said although half of the patients benefitted, it is also important to note the other half failed to achieve clinical benefit. Subsequently, further investigation is warranted to achieve better clinical outcomes.