As a result, they frequently arrive at hospital with advanced stages of breast cancer that are harder, more expensive and more painful to cure, said Stulac.
An estimated 70-80 percent of breast cancer cases are diagnosed at late stages in lower- and middle-income countries, according to Knaul.
But even with early diagnosis, breast cancer can mean a painful and debilitating death in cash-strapped countries where specialists are few and costs are high, said Stulac.
"Over the course of just seeking a diagnosis, [patients] have depleted their family's resources."
Cancer prevention and awareness campaigns are infrequent in low-income countries. And when cancer is diagnosed, treatment options can often include palliative care, which is scarce, expensive and stigmatized, according to 2011 oncology research.
The Vienna-based International Narcotics Control Board says 90 percent of the world's opiate supply for pain relief is consumed in the most developed countries, leaving little for poorer countries.
Gathering data
Knaul urged combating disease with data. "We have to help women to diagnose more, even when we don't have good access to treatment because that's how we'll get to know that the disease exists."
Since 1980, breast cancer cases globally have risen annually by 3.1 percent on average, according to recent reports, and continued rises are predicted by WHO.
As a complex group of diseases for which there are few national registries, and ones that lack access to diagnostics and treatment, cancer's true burden remains unknown in many developing countries.
"We need to research at a very basic level of understanding what the disease looks like. We need better data," said Stulac.
Knaul's report called for public health systems to boost cancer detection alongside anti-poverty, maternal and child health, sexual and reproductive health and HIV/AIDS programming.
Breast cancer clinical trials in lower and middle-income countries can help boost tracking and prevention - sorely lacking and almost non-existent in some places, said Ismail Jatoi, chief of surgical oncology at the US-based Texas University Health Science Centre.
"Conducting trials in these countries is a way of setting up infrastructure within [health] centres that are conducting trials."
While an estimated eight out of 10 cancer cases worldwide are diagnosed in poorer countries, research there only attracts 5 percent of global cancer funding, according to the Global Task Force on Expanded Access to Cancer Care and Control.
"When research and science have helped us come up with newer and better medications, one of our goals should be to advocate for bringing those medications not just [to] rich people, but [to] poor people as well," said Stulac.