NEW DELHI — Alka Kudesia needs an expensive drug to treat her breast cancer, but refuses to tell her children for fear they will take out loans to buy the medicine and spend the rest of their lives in debt.

"We're barely able to afford the treatment I'm already getting," Ms. Kudesia, 48, said with quiet defiance. "My kids are just starting out in life. There is no way I'm going to be a burden to them."

The drug, Herceptin, is one of the most effective treatments for an aggressive form of breast cancer. But in India, at a cost of at least $18,000 for one course of treatment, only a small fraction of the women who need it get it.

The Indian government last year threatened to allow production of less costly, generic versions of Herceptin. Its maker, Roche Holdings of Switzerland, initially resisted, but surrendered its patent rights this year in large measure because it concluded that it would lose a legal contest in Indian courts.

The skirmishing over Herceptin and other cancer medicines is part of a new and critical phase in a long-running struggle to make drugs affordable to the world's poorest people, one that began in earnest more than a decade ago when advocates campaigned successfully to make AIDS medicines accessible to millions of Africans.

"Cancer is the next H.I.V./AIDS issue, and the fight has only begun," said Shamnad Basheer, a professor of law at West Bengal National University of Juridical Sciences in Kolkata.

American trade officials have voiced concerns about India's treatment of drug patents, including its reasons for sometimes overriding them. President Obama discussed the issue this year with Prime Minister Manmohan Singh of India during a meeting in the Oval Office, administration officials said.

Executives in the international pharmaceutical industry, increasingly dependent on drug sales in emerging markets like India, China and Brazil, contend that India's efforts to cancel patents threaten the global system for discovering cures while doing little to resolve the health challenges most patients here face.

"We are open to discussing what the best way is to bring innovative medicines to patients," said Daniel Grotzky, a spokesman for Roche, which has a large portfolio of cancer medicines. "But a society that wants to develop new medicines and technology must reward innovation through a solid protection of intellectual property."

Some health experts say investing in earlier diagnosis of breast cancer and improved testing, surgery and access to radiation therapy is more important than access to expensive drugs. "Chemotherapy is not the major issue for cancer control in India," said Dr. Richard Sullivan, a professor of cancer policy and global health at King's Health Partners' Integrated Cancer Center in London.

But health advocates say similar arguments were made by the United States government and the pharmaceutical industry as they sought to protect patents on AIDS medicines through much of the 1990s, a stance that former President Bill Clinton has since said he regrets. It would be unfair to delay improving access to cancer drugs until India's broken system for cancer care was fixed, they say. They note that more than twice as many people in India die of cancer than of AIDS.

As the world has made progress against malnutrition and infectious diseases, more people are living into old age and dying of chronic illnesses like heart disease and cancer, which now cause two-thirds of deaths globally. In 2012, there were 14.1 million new cancer cases across the world and 8.2 million cancer deaths, according to the World Health Organization. And the number of breast cancer cases is growing. About 6.3 million women were living with the disease last year.

The rise in the cancer caseload is already a heavy burden on India's hobbled health system. Indian women, while less likely to get breast cancer than those in the United States, are far more likely to die of it. About 115,000 women here are diagnosed with breast cancer every year and in 2008 some 54,000 died from it, according to the World Health Organization.

At intersections in New Delhi, women carrying doctors' notes beg for money for their prescribed treatments. India has just 27 dedicated public cancer centers for 1.2 billion people. The government has promised to add an additional 50 in the coming years, but medical experts say even that will be grossly inadequate.

India, which is one of the world's leading producers of generic pharmaceuticals, has long viewed patent rights on medicines skeptically. It has already ruled invalid patents protecting exclusive sales of Novartis's Gleevec, Pfizer's Sutent and Roche's Tarceva, all cancer medicines. In a landmark decision last year, the government agreed that the patent protecting Bayer's Nexavar, also a cancer drug, was valid but overrode it anyway because a generic company promised to lower the price from $4,500 to about $140 per month of treatment.