A large sample of patients with pure mucinous breast cancer demonstrated a favorable prognosis. However, researchers also found an association with significant occult multicentricity/multifocality.

"Our findings indicate another potentially unfavourable aspect associated with a widely accepted as favourable breast cancer subtype," said Dr. George H. Perkins, associate professor in the Division of Radiation Oncology at The University of Texas M. D. Anderson Cancer Center, USA.

"In an era of concern regarding overtreatment, we caution in our findings that undertreatment could also become a significant hazard for patients and thus should be a significant area of concern," he said.

Perkins presented results of this study at the CTRC-AACR Annual San Antonio Breast Cancer Symposium, USA.

Mucinous carcinoma is a rare form of cancer, diagnosed in about 2 percent of patients with breast cancer. Cancer cells within the breast produce mucous, forming a jelly-like tumor. Previous research has shown that the disease has a favorable prognosis; therefore, investigators have recommended treating patients with the minimal effective therapy vs. the maximum tolerated treatment.

"Our results are from one of the largest single institution experiences with a relatively uncommon subtype and has significant, long-term follow-up of patients," Perkins said. "We emphasise multidisciplinary, comprehensive care to avoid the non-recognition of additional occult disease, which could affect patient outcomes."

Perkins and colleagues reviewed charts for 264 patients diagnosed with a pure mucinous carcinoma from 1965 to 2005.

At five years, overall survival was 95 percent; the 10- and 15-year rate was 97 percent. Rates for distant metastases-free survival were similar: 88 percent at five years; 95 percent at 10 years; and 94 percent at 15 years. The five-year local regional control rate was 83 percent; at 10 years it was 92 percent; and at 15 years it was 85 percent.

Initially, 10 percent of the patients had a multicentric/multifocal presentation; however, a detailed pathology review revealed a 38 percent rate of multicentric/multifocal disease after resection. This finding surprised the researchers.

"We have been previously surprised by the decreasing age at presentation in this population, and by the regression of favorable outcomes towards the lower outcomes of other common breast cancer subtypes over time," Perkins said. "This reinforces our commitment to interdisciplinary care and true personalized patient treatment in this variant. Patients should receive the care indicated, rather than receive the assumption that it may not matter which treatment approach is taken because this is a favorable disease."

The researchers hope that these data, coupled with other data, will help practitioners understand the various presentations of favourable breast cancer subtypes. They also plan to "identify patients who may need additional multidisciplinary evaluation prior to disposition to a minimalist approach inclusive of observation and limited use of radiation therapy," Perkins said.

Source: www.sabcs.org