Surgery to remove a cancerous kidney can often lengthen the lives of patients but only about three in ten such patients undergo the procedure, a new study finds.

About 60,000 people each year are diagnosed with kidney cancer, and about 14,200 people will die of it.  It is the seventh most common cancer in men, and the 10th most common in women.

Using the National Cancer Data Base, researchers at Dana-Farber Cancer Institute and Brigham and Women’s Hospital in Boston reviewed the cases of 15,390 patients with malignant kidney cancers that were treated with targeted therapies between 2006 and 2013. Only 5,374 of those patients, or about 35 percent of the total, underwent surgical removal of the tumor, the researchers found.

This was the case, even though current guidelines call for surgery to be performed in addition to targeted treatment on for patients deemed to be good candidates for the procedure. Studies have shown that patients with poor survival outcomes or with rapidly advancing cancer are less likely to benefit from the surgery.

Patients who underwent the procedure along with receiving targeted therapy survived for a median period of 17.1 months, the researchers found, compared to 7.7 months for those who didn’t receive the surgery.

The investigators also found that patients who were younger, privately insured, treated at an academic medical center, and had smaller tumors are more likely to have the surgery performed.

It’s unclear why the surgery provides a survival benefit for many patients, investigators say, but they theorize that the primary tumor may be especially aggressive and drive metastatic growth elsewhere in the body. Removing it may therefore slow the spread of the disease.

“The study underscores the importance of careful selection of patients who are good candidates for this surgery. As we become better able to identify patients likely to derive the greatest benefit from surgery, survival rates may further improve,” said Maxine Sun, the co-lead author of the study, which appears in the  Journal of Clinical Oncology.