The growing scarcity of sterile, injectable drugs is one of the biggest issues confronting hospitals across the country, and will be a key issue at the annual American Society of Clinical Oncology meeting in Chicago this weekend.

Health officials blame the shortages on industry consolidation that has left only a handful of generic manufacturers of these drugs, even as the number of drugs going off-patent is growing. Some drugmakers have been plagued by manufacturing problems that have shut down multiple plants or production lines, while others have stopped producing a treatment when profit margins erode too far.

Some medicines have been periodically short in the past, doctors and pharmacists say, but the number of drug shortages has escalated in recent years, jumping from 56 in 2006 to 250 last year, according to U.S. Food and Drug Administration figures.

Generic drugmakers like U.S.-based Hospira Inc and Israeli Teva Pharmaceutical Industries say they are building new facilities to prevent future shortages.