Not long before Mihir Shah was to be married in 2007, his soon-to-be mother-in-law got a diagnosis of breast cancer. She underwent chemotherapy and survived, wearing a wig to the wedding.

But while the women in Mr. Shah’s family — in both India and the United States — were able to get breast cancer screening, it made him think of the millions who weren’t as fortunate.

More than 90 percent of women in the developing world don’t have access to early detection of breast cancer. One reason is that mammograms, the gold-standard screening technique, are rarely used because of their high cost and a lack of trained radiologists. India has one radiologist for every 100,000 people; the United States has 12.

Then there are logistical challenges like a lack of electricity and poor roads. Many people are not aware of cancer, and the disease still carries a stigma.