A rare and deadly form of breast cancer, invasive lobular carcinoma (ILC), is on the rise in the United States, with cases increasing at a pace that outstrips other forms of the disease. Experts are raising alarms about this concerning trend, noting that ILC’s rapid rise presents challenges in detection, treatment, and long-term survival, particularly as it affects younger populations in addition to older ones. The increase in ILC cases has also led researchers to emphasize the need for more research into its unique biology and the development of targeted early detection and prevention strategies.
What is Invasive Lobular Carcinoma (ILC)?
Invasive lobular carcinoma is a subtype of breast cancer that originates in the lobules, the milk-producing glands of the breast. Unlike the more common ductal carcinoma, which forms a distinct lump, ILC cells grow in a dispersed, linear pattern. This means that ILC often doesn’t present as a palpable lump, making it more difficult to detect through traditional mammograms and physical exams. As a result, many cases are diagnosed later, when the cancer has already spread to other parts of the body.
Though ILC represents just over 10% of all breast cancer diagnoses, its rising incidence and distinctive biological behavior are making it a focal point of cancer research. The cancer’s growth pattern often leads to its spread to unusual locations, which poses significant challenges for both early detection and treatment.
Rising Rates of ILC: A Disturbing Trend
Researchers have recently reported that the incidence of invasive lobular carcinoma is climbing at a startling rate. Between 2012 and 2021, the annual incidence of ILC increased by 2.8% among women aged 50 and older, and 2.9% among women younger than 50. These rates are more than three times higher than the average annual increase for all other types of breast cancer combined, which stands at 0.8%.
The situation has become even more concerning between 2016 and 2021, with the annual increase in ILC cases accelerating to 3.4%. This steep rise in cases is contributing to growing concern among experts, particularly because it is occurring in both younger and older populations alike, unlike other forms of breast cancer that typically show more variation in incidence across age groups.
Disproportionate Rise Among Asian American/Pacific Islander (AAPI) Women
One of the most striking findings from the American Cancer Society’s research was the disproportionate rise in ILC cases among Asian American/Pacific Islander (AAPI) women. Between 2012 and 2021, the rate of ILC diagnoses in this group increased by 4.4% per year, the fastest rise among any racial or ethnic group in the U.S.
However, despite this rapid increase, white women still have the highest overall rates of ILC, with nearly 15 cases per 100,000 women. In comparison, Black women have 11 cases per 100,000, and AAPI women have around seven cases per 100,000. This suggests that while ILC is becoming more common across the board, it is particularly concerning in certain populations, raising questions about the potential interplay between genetics, lifestyle, and environmental factors.
Unique Challenges in Detection and Treatment
ILC’s distinct growth pattern makes it more difficult to detect early compared to other forms of breast cancer. Traditional mammograms and physical exams, which are designed to detect lumps and irregularities, are less effective at identifying ILC. This means that many cases are not diagnosed until the cancer has already spread beyond the breast, complicating treatment options.
While ILC is not categorically more aggressive than other types of breast cancer in terms of its initial metastasis, its tendency to spread in unusual patterns and to less common parts of the body makes it harder to manage. This unique form of spread often leads to delayed diagnoses and presents challenges in monitoring disease progression.
Moreover, ILC has been found to be less responsive to chemotherapy than other types of breast cancer, adding another layer of difficulty in treating the disease. This, combined with the difficulty in detecting ILC at earlier stages, has contributed to the disease’s poorer long-term survival rates compared to more common breast cancer types, such as ductal carcinoma.
Survival Rates and Long-Term Outlook
While the five-year survival rate for women with ILC is relatively similar to that of other breast cancers, the ten-year survival rate is significantly lower. This disparity arises because ILC has a higher risk of late recurrence and tends to spread to uncommon sites in the body, where it is harder to treat. For ILC that has spread distantly, the 10-year survival rate is only 12.1%, compared to 19.6% for ductal breast cancer.
Early-stage ILC may present a better prognosis, but the long-term outlook is much less favorable once the cancer has spread to other organs. Senior researcher Rebecca Siegel from the American Cancer Society noted that while ILC has a relatively good prognosis in the short term, its long-term survival rates are concerning, especially in cases where the disease has metastasized.
Lifestyle and Hormonal Factors Driving the Rise in ILC
The increase in ILC cases is largely attributed to lifestyle and hormonal factors rather than genetic predispositions. Researchers have pointed to several risk factors that contribute to the rise in ILC, including:
- Increased body weight, which is strongly associated with a higher risk of breast cancer.
- Earlier onset of menstruation and later menopause, both of which extend a woman’s exposure to estrogen, a hormone that promotes the growth of certain types of breast cancer.
- Fewer children or having a first child at an older age, which also prolongs estrogen exposure.
- Increased alcohol consumption, which has been linked to higher risks of various types of cancer, including breast cancer.
Hormonal therapy, particularly during menopause, has also been found to contribute to the rising rates of ILC. When the use of hormone therapy decreased in recent years, the rate of ILC cases also started to drop, pointing to a strong association between hormonal exposure and the disease’s rise.
The Need for Targeted Research and Early Detection
Despite the rapid rise in ILC cases, this cancer subtype remains understudied compared to other more common forms of breast cancer. Experts argue that more attention needs to be given to understanding ILC’s unique biology, developing targeted early detection methods, and exploring preventative measures.
Researchers emphasize that ILC requires specific research and clinical trials to better understand its causes, improve its treatment, and ultimately improve survival outcomes. As the number of new diagnoses continues to rise, there is a growing sense of urgency to address the unique challenges posed by this form of breast cancer.
Moving Forward: The Way Ahead
The invasive lobular carcinoma (ILC) surge among both young and older women presents a complex challenge for public health, researchers, and medical professionals. While its early-stage survival rates are promising, the cancer’s tendency to spread unpredictably makes it a critical issue for long-term care and research. With lifestyle factors driving much of the increase, there is a pressing need for more awareness and preventative strategies. As researchers like Angela Giaquinto and Rebecca Siegel emphasize, focusing on ILC’s biology and improving detection could help lower its impact in the future.
