Recent research indicates that rates of a rare yet highly deadly cancer, known as invasive lobular carcinoma (ILC), are on the rise in the United States. This alarming trend shows that cases are increasing at a rate three times faster than all other forms of breast cancer. Between 2012 and 2021, the incidence of ILC climbed at an average annual rate of 2.8 percent among women aged 50 and older, and 2.9 percent among younger women under 50. In stark contrast, the overall increase for all other types of breast cancer combined was only 0.8 percent.
The period from 2016 to 2021 has raised particular concern among health experts, as it exhibited an even sharper annual increase of 3.4 percent in cases of invasive lobular carcinoma. Researchers from the American Cancer Society revealed that the most significant rise in ILC cases was observed among Asian American and Pacific Islander (AAPI) women, who experienced a 4.4 percent annual increase. Despite this rapid growth in certain demographics, white women continue to hold the highest overall case rate, with nearly 15 cases per 100,000 women, compared to 11 per 100,000 among Black women and about 7 per 100,000 among AAPI women.
According to Angela Giaquinto, the lead researcher and an associate scientist for cancer surveillance research at the American Cancer Society, "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 growth pattern of ILC differs from other breast cancers; it tends to proliferate in dispersed patterns rather than forming distinct lumps, which complicates detection and treatment. While this growth pattern does not necessarily make ILC more aggressive in terms of metastasis, it does result in unique challenges, as the cancer can spread to unusual locations within the body.
Researchers conducted an extensive analysis of national cancer data, comparing cases of invasive lobular carcinoma to all other types of breast cancer. They utilized specialized software to calculate rates and identify statistical differences in trends. The study also examined patient and tumor characteristics between lobular and ductal cancers, as well as their respective ten-year survival rates. While ILC shares a similar five-year survival rate with other breast cancers, its long-term prognosis is less favorable. The ten-year survival rate for ILC is notably lower, primarily due to a higher risk of late recurrence and its tendency to spread to uncommon sites in the body. For lobular cancer that has metastasized, the ten-year survival rate is only 12.1 percent, compared to 19.6 percent for the more common ductal cancer.
The increasing prevalence of lobular breast cancer, combined with its low long-term survival rates, highlights the urgent need for enhanced prevention and early detection strategies tailored to this subtype. Giaquinto emphasizes the importance of this issue, stating, "Also, survival rates beyond seven years are significantly lower for lobular breast cancer than for the most common type of breast cancer, underscoring the need for targeted research." The unique biology of ILC, which complicates detection and may reduce responsiveness to chemotherapy, necessitates a focused research effort to improve outcomes for patients.
Interestingly, cases of ILC are rising consistently across all age groups, with no significant variation observed between younger and older populations. Researchers attribute this trend primarily to hormonal and lifestyle risk factors rather than genetics. ILC is found to be "more strongly associated with female hormone exposure" compared to other breast cancers. This is evidenced by a notable decline in ILC cases following reduced hormone therapy usage among menopausal women. Additionally, rising rates of excess body weight, earlier onset of menstruation, and having fewer children or delaying childbirth are identified as contributing factors to the increased incidence of ILC. Other significant contributors include factors that prolong a woman’s lifetime exposure to estrogen, such as a later age at menopause and increased alcohol consumption among certain groups.
The findings of this study, published in Cancer, the journal of the American Cancer Society, emphasize the necessity for more comprehensive information on lobular cancers across various domains, including genetic studies and clinical trial data. As senior researcher Rebecca Siegel stated, "Our study underscores the need for much more information on lobular cancers across the board, so we can improve outcomes for the increasing number of women affected by this cancer." With the rising rates of invasive lobular carcinoma, focused research and public awareness are crucial to combat this growing health concern.
