(NBC NEWS) -- A new study is once again raises the question of when women should start getting mammograms to screen for breast cancer.
The new study from researchers at Harvard Medical School finds a majority of women who die of breast cancer don't get regular screening mammograms.
"It looks like the majority of deaths occur in the minority of patients that are not getting screened," said Harvard's Dr. Blake Cady.
What's more, half of the patients who died in the study were under age 50.
The researchers suggest this means all women should be encouraged to undergo mammograms at an earlier age.
"They should treat mammogram screening like an insurance policy," Cady said.
But while recognizing the important role of breast cancer screening for many women, other breast cancer experts urge more caution.
"The value of mammography is less than many people assume," said Dr. Michael LeFevre with the U.S. Prevention Services Task Force.
In 2009 the U.S. Preventive Services Task Force concluded that most women do not need to start regular mammograms until age 50.
Not all breast cancers are alike and the task force says the deadly tumors that typically develop in younger women grow very quickly and there's no strong evidence that a mammogram would catch them in time or even help save the patient's life.
"Unfortunately, the cancers we most want to impact, the most aggressive cancers are least amenable to screening,"LeFevre said.
Some groups like the American Cancer Society recommend annual mammogram starting at age 40.
Women are encouraged to talk to their doctors about what's right for them.