Cancer Congress Highlights New Findings On Advanced Breast Cancer

The ESMO Congress 2021 saw results of a Phase 3 trial of ribociclib, a CDK4/6 inhibitor, that showed a median overall survival of 63.9 months for metastatic breast cancer with a good safety profile, besides maintaining quality of life with a 12-month delay for chemotherapy.

KUALA LUMPUR, Feb 4 – The European Society for Medical Oncology’s (ESMO) 2021 congress highlighted targeted therapy for advanced breast cancer, the impact of Covid-19 on cancer patients, and unmet needs of cancer survivors, among others.

Around 2,000 abstracts were presented at the conference in Lugano, Switzerland, last September.

The ESMO Congress 2021 also noted the “particular scientific relevance” of results from Phase Three trials with immunotherapy in HER2+ metastatic breast cancer, melanoma, colorectal cancer, lung cancer, advanced adenocarcinoma, and metastatic cervical cancer.

Abstracts selected for press releases included long-term estimates of cancer incidence and mortality for the European Union (EU) and European Free Trade Association (EFTA) countries, perceptions of non-oncologist physicians regarding cancer patients’ prognosis, as well as European cancer patients’ perspectives on immunotherapy.

In Malaysia, most women with advanced breast cancer in Stage Four can expect to live only a year, according to the 2018 Malaysian Study on Cancer Survival (MySCan).

The MySCan report by the National Cancer Institute shows that 66.8 per cent of patients with Stage Four breast cancer, or metastatic breast cancer where the tumour has spread to other organs, have one-year relative survival.

Only 35.6 per cent of Stage Four breast cancer patients in Malaysia have three-year relative survival, and just 23.3 per cent have five-year relative survival. Relative survival is the comparison of survival rates between people who have a specific disease and those who don’t over a certain period of time.

A team of scientists. Picture from Novartis.

However, a study of a new treatment presented at the ESMO Congress 2021 reported, for the first time ever, a “statistically significant and clinically meaningful overall survival benefit” for women with advanced breast cancer.

The Phase Three trial of ribociclib, in combination with letrozole, showed a median overall survival of more than five years, or 63.9 months, for metastatic breast cancer, about one year longer than 51.4 months with hormone therapy alone. It showed that ribociclib prolonged overall survival by one year in postmenopausal women with HR positive, HER2 negative advanced breast cancer. Overall survival means how long one stays alive with the disease.

The estimated six-year survival rate was 44.2 per cent with ribociclib, a CDK4/6 inhibitor, compared with 32 per cent for combined placebo and endocrine therapy letrozole.

“These remarkable ribociclib overall survival data are highly encouraging and represent the longest reported median overall survival from a randomised trial in HR+/HER2- advanced breast cancer.

“This extension of life is great news for our patients and the building block for further progress,” said Dr Gabriel N. Hortobagyi, a professor of medicine with the University of Texas MD Anderson Cancer that led the study, in a press statement.

“To put these results into perspective, in my 45 years as an oncologist there have been tens of thousands of clinical trials for breast cancer and while a PFS (progression-free survival) benefit has been shown many, many times, we have rarely observed an improvement in overall survival. PFS refers to the duration of disease remaining under control without getting worse.

“It is difficult to show a statistically significant extension in survival for first-line therapy in this type of breast cancer because due to the development of resistance, patients receive four to 15 different types of treatment over the course of their disease and these dilute the effect of the first therapy,” he added.

The final overall survival analysis of the Phase Three Monaleesa-2 study was made after a median follow-up of over six and a half years, the longest for any CDK4/6 inhibitor trial to date.

Prof Giuseppe Curigliano, clinical director of the Division of Early Drug Development for Innovative Therapy at the European Institute of Oncology in Milan, Italy, noted that the study data related to endocrine-sensitive patients who had not previously received endocrine therapy for metastatic disease.

“The clinical implication is that now we have a clear demonstration that the combination of endocrine therapy plus the CDK 4/6 inhibitor ribociclib prolongs both progression-free survival and overall survival,” Curigliano was quoted saying in a September 19 press release by ESMO Congress.

The Monaleesa-2 trial also showed that the time to first chemotherapy treatment was 50.6 months for participants who received ribociclib, compared to 38.9 months for placebo combined with letrozole. This means ribociclib led to a 12-month delay for chemotherapy, compared to those taking letrozole alone.

The longer follow-up in the trial flagged no new safety signals; adverse events were consistent with previously reported Phase Three Monaleesa-2 trial results, with neutropenia being the most common adverse event. (Neutropenia is a condition where one has an unusually low number of neutrophils, a type of white blood cell).

“I am very encouraged that metastatic breast cancer patients may have a treatment option that extends survival, delays chemotherapy treatment and preserves their quality of life,” said Dr Hortobagyi in a September 19 news release by MD Anderson Cancer Center.

“Given these results, the combination of a CDK4/6 inhibitor plus an aromatase inhibitor should be the standard first-line treatment for the majority of patients with advanced hormone receptor–positive breast cancer,” he added. “These findings have the potential to impact most women diagnosed with metastatic breast cancer.”

A scientist measuring results. Picture from Novartis.

The international Monaleesa-2 study enrolled 668 postmenopausal women with advanced breast cancer at 223 trial sites in 29 countries across Western Europe, the Americas, and East Asia.

They were randomised to receive either ribociclib and letrozole, or letrozole and placebo. None had been previously treated for their advanced disease. Trial participants were 82.2 per cent white, 7.6 per cent Asian, 2.5 per cent Black and 7.6 per cent other ethnicities.

Dr Hortobagyi, who presented the findings at the ESMO Congress, said the trial results could be extrapolated to HR positive, HER2 negative metastatic breast cancer patients regardless of their ethnicity.

“When treatment offers long overall survival — and in this case, the longest ever reported in HR+/HER2- advanced breast cancer — patients have more time to be with family and loved ones and to pursue whatever makes them happy.

“These data offer new hope for people with advanced or metastatic breast cancer, which remains the leading cause of cancer death in women worldwide,” said Shirley A. Mertz, president of the Metastatic Breast Cancer Network.

The Phase Three trial results on ribociclib — which has been approved by the United States’ Food and Drug Administration (FDA) — are welcome, especially since breast cancer patients in Malaysia are increasingly presenting in the late stages of Three and Four, according to the Malaysia National Cancer Registry Report 2012-2016.

According to that report, the percentage of female breast cancer cases for the early stages of 1 and 2 declined from the 2007-2011 period to 2012-2016: Stage One (from 19.9 per cent to 17.5 per cent) and Stage Two (from 37 per cent to 34.5 per cent). In comparison, the proportion of late-stage breast cancer cases increased over the same period: Stage Three (from 23.1 per cent to 25.1 per cent) and Stage Four (from 20.1 per cent to 22.8 per cent).

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