A survey of leading U.S. cancer centers released on Thursday illuminates the degree to which they are struggling to obtain medications for their patients, with nearly all identifying some shortages of critical generic therapies.

In late August, the National Comprehensive Cancer Network surveyed, pharmacy directors and other clinical and administrative leaders at ​its 34 member institutions about drug shortages.

Among the ​31 centers that responded, all said they ⁠are experiencing a shortage of at least one anti-cancer agent, and more than 20% said they currently have shortages of five or more different medications.

A shortage of ifosfamide, a generic chemotherapy used for bladder, ovarian, testicular, uterine, soft tissue sarcoma, osteosarcoma, and blood cancers, was reported by 94% of ​respondents.

In addition, 71% reported a shortage of carboplatin and 16% were short on cisplatin, which are important chemotherapies used as the backbone of ​regimens to treat numerous ⁠different tumor types, the NCCN said.

The immunotherapy Bacillus Calmette-Guérin for bladder cancer was also in short supply for more than half of the respondents.

When treatment plans had to be modified as a result of these drug shortages, 90% of centers noted a need for repeat prior authorization of the plan by insurance companies, significantly increasing the amount of work per patient and adding in the potential for a delay ⁠in care ​continuity, the NCCN researchers said.

“Nearly every pharmacy director who responded to our survey would like to see economic incentives ​put in place to encourage high-quality manufacturing for generic cancer medications,” Alyssa Schatz, NCCN’s vice president of policy & advocacy, said in a statement.

“That is something that advocates have been requesting for years,” she said. “As one respondent noted: ‘many oncology generics are ​clinically indispensable but economically unattractive. Without correcting that economic imbalance, shortages are likely to recur.’”