Express Scripts Holding Co., a large manager of prescription-drug benefits for U.S. employers and insurers, is seeking deals with pharmaceutical companies that would set pricing for some cancer drugs based on how well they work.

The effort is part of a growing push for so-called pay-for-performance deals amid complaints about the rising price of medications, some of which cost more than $100,000 per patient a year.

Some insurers and prescription-benefit managers are pushing back by arguing that they should pay less when drugs don’t work well in certain patients. Drug companies are countering with pricing models of their own, such as offering free doses during a trial period.

Express Scripts this month told clients it is seeking deals with drug makers for differentiated pricing for certain cancer drugs based on how well they work against different types of tumors, Express Scripts Chief Medical Officer Steve Miller said in an interview. Currently, Express Scripts and most insurers pay the same per-unit rate for a cancer drug regardless of the type of cancer it is being used to treat.

Dr. Miller pointed to Tarceva, a drug co-marketed by Roche Holding AG and Astellas Pharma Inc., which has shown a smaller benefit in pancreatic cancer than in lung cancer. In one clinical trial, Tarceva extended the median survival of pancreatic cancer patients by less than two weeks versus placebo. In a separate trial, it prolonged survival among lung cancer patients by about 3 ½ months versus chemotherapy.