A PROMISING SCREENING TOOL FOR RENAL CANCER 

A new immunoassay shows promise as a screening tool for detecting early renal cell carcinoma (RCC).

The test measures the levels of 3 biomarkers: nicotinamide N-methyltransferase (NNMT), L-plastin (LCP1), and nonmetastatic cells 1 protein (NM23A). Plasma levels of all 3 were found to be highly elevated in patients with kidney cancer.

"If this [assay] is truly valid and accurately detects renal cell carcinoma, a number of patients...could potentially be saved through early diagnosis," said researcher Nam Hoon Cho, MD, from the Department of Pathology at Yonsei University Health System in Seoul, Korea.

In a statement, he pointed out that RCC is one of the most difficult forms of cancer to detect and treat because "it remains silent until disseminating to other organs."

"Because imaging, which is expensive, is seldom performed without any specific reason, developing a blood-tumor biomarker is a great chance to detect the silent killer," said Dr. Cho.

The study appears in the March issue of Cancer Epidemiology, Biomarkers & Prevention.

The incidence of RCC is increasing, note the researchers, with the highest prevalence in developed countries. The growing incidence is probably due to a combination of environmental factors and the increasing use of imaging, which leads to more detection.

However, the ability of imaging to distinguish between the various types of RCC is limited, and can be slow and labor intensive, the researchers note.

Asymptomatic RCC could be a leading cause of failed early detection of kidney cancer. Despite advances in the treatment of metastatic RCC, nephrectomy remains the only effective treatment for localized disease.

The researchers point out that there is currently no clinically relevant screening assay to detect asymptomatic RCC. Thus, there is "an urgent need for validated markers of RCC."

Dr. Cho and colleagues validated the 3-marker assay with 100 test samples. They then measured NNMT, LCP1, and NM23A concentrations in 189 plasma samples from 102 healthy subjects or patients with benign tumors and 87 patients with kidney cancer.

Plasma levels of NNMT, LCP1, and NM23A were highly elevated in patients with kidney cancer (P < .0001). For example, the median concentration of NNMT in the healthy control subjects was 68 pg/mL, whereas it was 420 pg/mL in patients with kidney cancer.

The diagnostic accuracy of NNMT alone was 0.913 and of the 3-marker assay was 0.932. However, when 90% specificity was defined, the sensitivity of the 3-marker assay was much better than for NNMT alone (95.7% vs 71.9%).

In addition, the positive predictive value of the 3-marker assay was 87.2%, and the negative predictive value was 97.0%.

The researchers note that the "limitation of each single marker was overcome with the 3-marker combination assay, leading to improved diagnostic accuracy."

They conclude that on the basis of these results, the 3-marker assay warrants validation in a multicenter study.

The study was supported by a National Research Foundation of Korea grant funded by the MEST and by the Korean Foundation for Cancer Center. The authors have disclosed no relevant financial relationships.

Cancer Epidemiol Biomarkers Prev. 2013;22;390-398. Abstract