New study questions true favorability of rare breast cancer type

The study, presented December 12 at the CTRC-AACR San Antonio Breast Cancer Symposium, is the first to observe this negative association and should caution those caring for mucinous breast cancer patients that more, not less, therapy, as well as additional screening may be needed for a select group of these patients, said George Perkins, M.D., associate professor in M. D. Anderson Department of Radiation Oncology and the study's first author.

Mucinous breast cancer, also known as colloid carcinoma, is a rare type of invasive breast cancer formed by mucus-producing cancer cells. Perkins estimated that the disease accounts for approximately two percent of all breast cancers diagnosed. The prognosis for mucinous carcinoma is thought to be better than for the more common types of invasive breast cancers.

"While mucinous breast cancer is thought to be a disease with a favorable prognosis, our study is the first to identify it as one associated with significant multifocal presentation -- a potentially unfavorable aspect with a subtype long thought to be extremely favorable," said Perkins. "Our findings must caution those caring for these women that they may not only need more radiographic evaluation, such as MRI, but also intraoperative collaboration with radiology and pathology. These patients also may need standard radiation treatment, rather than the minimal effective therapy, which could include no post-surgery treatment at all."

Researchers reviewed charts of 264 patients with mucinous carcinoma treated at M. D. Anderson between 1965 and 2005. The median age and follow-up was 57 years and 168 months respectively. Of the patients, 86 percent were stage T2 or less, and 80 percent had no lymph node involvement, 15 percent had 1-3 positive nodes and 5 percent had 4 or more.

Regarding treatment, 44 percent of the women received breast-conserving therapy, and the rest underwent a mastectomy; 51 percent had radiation.

However, while 10 percent of the women first presented with more than one tumor, after surgical resection and complete pathological review, the actual rate of multifocal disease was 38 percent. None of these tumors were detected by mammography and/or ultrasound.

"This actual rate of multifocal disease was a tremendous surprise and of true concern," said Perkins. "We are also concerned that the age of disease presentation appears to be decreasing in this population. Combined with this trend of unfavorability, it's imperative that we continue to research personalized treatment options for this subtype and that patients receive their treatment based on actual presentation rather than the assumption that this is always a favorable disease."

The five, 10 and 15 year overall survival (OS), disease-free survival (DFMS), local-regional control (LRC) were: 95 percent, 88 percent, 83 percent; 97 percent, 95 percent, 92 percent and 97 percent, 94 percent and 85 percent, respectively. When analyzing surgical options, there was no statistically significant difference in overall OS, DFMS, or LRS. Likewise, there was no improvement in OS or DMFS in patients that received whole breast radiation. There was a trend, however, for improved LRC in patients who received radiation when comparing patients that underwent surgery without radiation.

As follow up, the researchers are evaluating a subtype of mucinous breast cancer thought to be exceedingly aggressive in hopes of establishing specific screening and treatment guidelines.

In addition to Perkins, other authors on the all-M. D. Anderson study include: Gildy Babiera, M.D., associate professor, Isabel Bedrosian, M.D., assistant professor, both of the Department of Surgical Oncology; Eric Strom, M.D., professor, Department of Radiation Oncology, Gary Whitman, M.D., professor, and Wei Yang, M.D., associate professor, both of the Department of Diagnostic Radiology; and Lavinina Middleton, M.D., associate professor, Department of Pathology.