Deadly rare cancer surges in young people as experts sound alarm due to 'sheer numbers'

Scientists are warning that rates of a rare but highly deadly cancer are on the rise in the US, with cases climbing three times faster than other forms of the disease.

A key finding from 2012 to 2021 was that the invasive lobular carcinoma (ILC), a type of breast cancer, incidence climbed at an average annual rate of 2.8 percent in women 50 and older and 2.9 percent among women younger than 50.

This rise across age groups exceeds the 0.8 percent increase for all other breast cancers combined.

The period from 2016 to 2021 was most concerning, showing an even sharper annual increase of 3.4 percent. Hormonal and lifestyle factors, not genetics, are the primary drivers behind the rising rates of invasive lobular carcinoma, experts say.

Researchers at the American Cancer Society reported this week that the steepest rise in lobular breast cancer cases was among Asian American/Pacific Islander (AAPI) women, with an increase of 4.4 percent per year.

Despite this rapid increase, white women still have the highest overall case rate with nearly 15 cases per 100,000 women, compared to 11 per 100,000 among Black women and approximately seven per 100,000 among AAPI women.

Lead researcher Angela Giaquinto, an associate scientist for cancer surveillance research at the American Cancer Society, said: ‘Although lobular breast cancer accounts for a little over 10 percent of all breast cancers, the sheer number of new diagnoses each year makes this disease important to understand.’

The lobular form of the disease appears to grow in ways that differ from the other breast cancers, with cells proliferating in dispersed patterns as opposed to forming a lump typical of other cancers.

The growth pattern of ILC doesn't make it categorically more aggressive in terms of metastasis, but it makes its spread differently, sometimes later, and to unusual locations, which poses unique challenges for detection and treatment.

Researchers analyzed national cancer data, comparing invasive lobular breast cancer cases against all other types to track incidence trends.

Using specialized software, they calculated rates and tested for statistical differences in trends.

The study also compared patient and tumor characteristics between lobular and ductal cancers and analyzed their ten-year survival rates.

While ILC has a similar five-year survival rate to other breast cancers, its long-term outlook is less favorable.

The ten-year survival rate is lower, largely because ILC has a higher risk of late recurrence and tends to spread to uncommon sites in the body.

For lobular cancer that has spread distantly, the 10-year survival rate is only 12.1 percent compared to 19.6 percent for the more common ductal cancer.

Lobular breast cancer is becoming more common, and its long-term survival rates are low once it spreads.

In addition to finding that rates of ILC are rising over three times faster than all other breast cancers, its slight survival advantage in the first few years disappears over time.

Giaquinto said: ‘Also, survival rates beyond seven years are significantly lower for [lobular breast cancer] than the most common type of breast cancer, highlighting the pressing need for prevention and early detection strategies targeting this subtype to be brought to the forefront.'

The authors conclude that ILC's unique biology, which makes it harder to detect and potentially less responsive to chemotherapy, requires specific research and clinical attention to improve these outcomes.

Senior researcher Rebecca Siegel, senior scientific director for cancer surveillance research at the ACS, said: ‘Invasive lobular breast cancer is very understudied, probably because of a very good short-term prognosis.

‘But at 10 years, these women with metastatic disease are half as likely to be alive as their counterparts with ductal cancer, probably because of the unique spread and resistance to therapy.’

Cases are occurring consistently across all age groups.

The uniform pattern is notable because ILC is rising at similar rates in both younger and older populations, unlike some other breast cancer types that typically show more variation between age groups.

Researchers pointed to hormonal and lifestyle risk factors as the main drivers of the increasing incidence over genetics.

ILC is described as being ‘more strongly associated with female hormone exposure’ than other breast cancers, evidenced by a steeper drop in ILC cases when menopausal women’s use of hormone therapy went down.

They also specifically pointed to the impacts of increasing rates of excess body weight, a younger age at first menstruation and having fewer children or having a first birth at an older age.

Factors that extend a woman's lifetime exposure to estrogen, such as a later age at menopause, along with increased alcohol consumption in some groups, are also identified as significant contributors to the growing number of cases.

Their research was published in Cancer, the journal of the American Cancer Society.

Siegel concluded: ‘Our study underscores the need for much more information on lobular cancers across the board, from genetic studies to clinical trial data, so we can improve outcomes for the increasing number of women affected with this cancer.’