WOMEN with an aggressive type of breast cancer lived longer if they received immunotherapy plus chemotherapy, rather than chemo alone, a major study has found.
The results are expected to change the standard of care for women like those in the clinical trial, who had advanced cases of “triple-negative” breast cancer. That form of the disease often resists standard therapies, and survival rates are poor. It is twice as common in African-American women as in white women, and more likely to occur in younger women.
Researchers said the new study was a long-awaited breakthrough for immunotherapy in breast cancer. Until now, most progress had been in other cancers, including lung cancer and melanoma, an aggressive skin cancer.
These findings may lead to the first approval by the Food and Drug Administration for an immunotherapy drug to treat breast cancer. But the approval would likely be limited to a certain type of aggressive cancer.
Although triple-negative tumours occur in only about 15 per cent of patients with invasive breast cancer in the United States (or nearly 40,000 each year), they account for a disproportionate share of deaths, as many as 30 per cent to 40 percent.
The term triple-negative refers to the tumours’ lack of sensitivity to the hormones estrogen and progesterone, and their lack of a protein called HER2, which is a target of treatment.
The immunotherapy in the study was atezolizumab (brand name Tecentriq), which belongs to a class of drugs called checkpoint inhibitors; the chemotherapy was nab-paclitaxel (Abraxane).
The findings were published on Oct 13 in the New England Journal of Medicine, and were to be presented at a meeting of the European Society for Medical Oncology, in Munich. The study included 902 patients treated at 246 medical centres in 41 countries.
Checkpoint inhibitors like atezolizumab work by helping T-cells — a type of white blood cell that is part of the immune system — recognise cancer and attack it. Research that led to these drugs won this year’s Nobel Prize in medicine.
The drugs generally work for fewer than half of patients but can bring lasting recoveries even to people who were severely ill. Side effects can be dangerous, even life-threatening, and treatment costs more than US$100,000 (RM416,000) a year.
In other cancers, researchers sometimes describe the tumours as “hot”, meaning they tend to have many mutations — genetic abnormalities that the immune system can recognise as foreign and attack.
But breast cancers tend to be relatively “cold”, with fewer mutations. The immune system is less likely to recognise them as invaders, which may help explain why previous studies of checkpoint inhibitors in breast cancer have been somewhat disappointing, researchers say.
In the new study, the key to success seems to have been giving chemotherapy along with immunotherapy.
The chemo may help to ignite the immune system, in part by killing cancer cells that then spill substances the T-cells detect as foreign and begin to hunt.
The new study “is a big deal and has been the buzz of the breast cancer research world”, said Dr Larry Norton of Memorial Sloan Kettering Cancer Centre. He was not involved in the study.
Beyond changing treatment practices, he said the research “opens the door to new approaches to harness the immune system to fight breast cancer, and there is every reason to expect major advances there”.
He cautioned that the combined treatment would have to be studied further, to assess side effects.
The women in the study had triple-negative breast cancer that had been newly diagnosed and had become metastatic, meaning it had begun to spread. Once that occurs, the outlook is grim, with many patients surviving 18 months or less.
Half received chemo alone, and half were given chemo plus immunotherapy.
Among those who received the combination, the median survival was 21.3 months, compared with 17.6 months for those who received chemo alone. The difference was not statistically significant.
But when the researchers looked at women who had a marker called PD-L1 on their cancer cells, the results were striking: The median survival was 25 months in the combination group, versus 15.5 months with just chemo. That finding has not been analysed statistically, and the patients are still being followed.
Doctors say the survival difference is important.
“This is truly a game changer,” said Dr Sylvia Adams, an author of the study from NYU Langone Health’s Perlmutter Cancer Centre.
Cancer patients with the PD-L1 marker tend to respond better to checkpoint inhibitors than those without it. In this study, 41 per cent of patients had the marker.
Adams said some patients, after initial treatment with both types of drug, have been doing well for two or three years with immunotherapy alone.
The “million-dollar question,” she said, is whether they can safely stop the immunotherapy if they have no sign of cancer. For the time being, they are sticking with the treatment. NYT