According to a study published in the journal Lancet Oncology, higher tumor levels of a protein known as IMP3 are linked with worse survival and an increased risk of metastasis among patients with kidney cancer.
The kidneys are each filled with tiny tubules that clean and filter the blood-the process that removes waste and makes urine. Renal cell cancer (RCC) is a malignancy involving these tubules of the kidney. Metastatic RCC refers to cancer that has spread from the kidney to distant sites in the body.
Kidney cancer that has not spread to distant sites in the body is often curable by surgery to remove the cancer. Some patients, however, eventually develop distant metastases. The ability to predict which patients are most likely to develop metastases could influence patient treatment and would provide important information about prognosis.
IMP3 is a protein that is usually expressed during early stages of human development (before birth). Levels of IMP3 in adults are generally low or undetectable. The role of IMP3 is uncertain, but it may regulate cell proliferation.
Because IMP3 has been identified in certain types of cancer-including cancers of the pancreas, lung, stomach, and colon-researchers evaluated whether IMP3 could be identified in RCC tissue, and whether IMP3 was linked with RCC prognosis and metastasis.
The study evaluated 371 patients with stage I to stage III RCC. The study found that survival was better and the risk of metastasis was lower in the patients whose tumors did not express IMP3.
• Among patients with stage I RCC, the probability of surviving for at least five years without cancer metastasis was 98% among those without IMP3 expression and 44% among those with IMP3 expression.
• Similar patterns were observed for patients with stage II or stage III RCC. Among patients with stage II RCC, the probability of surviving for at least five years without cancer metastasis was 94% among those without IMP3 expression and 41% among those with IMP3 expression. Among patients with stage III RCC, the probability of surviving for at least five years without cancer metastasis was 62% among those without IMP3 expression and 16% among those with IMP3 expression.
• After accounting for factors such as age, tumor stage, and tumor grade, IMP3 expression was linked with a four-fold increase in risk of death.
The researchers conclude that the level of IMP3 in kidney tumor tissue provides important information about prognosis. Information about IMP3 may help identify patients who have a high risk of metastasis; these patients might benefit from more intensive treatment.
Reference: Jiang Z, Chu PG, Woda BA et al. Analysis of RNA-binding Protein IMP3 to Predict Metastasis of Renal-cell Carcinoma: A Retrospective Study. Lancet Oncology. 2006;556-64.