MANCHESTER, ENGLAND – Older women with primary, operable, triple-negative breast cancer may have less aggressive tumor biology despite being treated for larger tumors than their younger counterparts, new data suggest.
Tumor samples taken from women aged 70 years or older were found to be of lower grade with significantly lower expression of the tumor markers Ki67 and p53 than seen in younger women, investigators reported at the annual meeting of the International Society of Geriatric Oncology (SIOG).
These data may help explain why similar clinical outcomes were achieved despite aggressive adjuvant chemotherapy not being given to the more elderly women, said investigator Dr. Kwok-Leung Cheung, of the University of Nottingham, England. "The precise place of adjuvant chemotherapy in the treatment of these patients has yet to be defined," he said.
The new report adds to previous findings presented at the American Society of Clinical Oncology (ASCO) meeting in 2011, (J. Clin. Oncol. 2011;29:abstr 1057), Dr. Cheung noted.
At ASCO, Dr. Cheung and his coauthors reported that they had identified 127 older women with triple-negative breast cancer among more than 2,000 women, aged 70 years and older, who had been treated over a 36-year period (1973-2009) for early operable primary breast cancer at a single clinic and also who had good quality tumor samples available for tissue microarray analysis using indirect immunohistochemistry.
The initial study compared this group’s results with those of 342 women with triple-negative breast cancer in a previously characterized consecutive series of 1,809 patients treated at the same clinic from 1986 to 1998. The rates of 5-year breast cancer-specific survival (73% vs. 79%) and of local (10% vs. 14%), regional (11% vs. 14%), and distant (30% vs. 27%) recurrences were found to be similar in younger and older women, respectively.
"Despite not having received adjuvant chemotherapy, the older series had clinical outcome similar to the younger patients, almost half of which had chemotherapy," Dr. Cheung and team reported at the time.
The current investigation, therefore, looked to see whether age was an important factor in determining clinical outcome, and if so, whether there were any biologic markers.
Older women were found to be more likely to have larger tumors than do younger women, with 66.7% and 50.4% (P = .002), respectively, having tumors of 2 cm or greater in size. There was no difference between them in axillary stage or nodal status.
Fewer women aged 70 years and above had grade 3 tumors: 79.8%, vs. 90.9% of the younger women (P = .007).
Biomarker analysis showed 48% vs. 87.7% (P less than .001) of tumor samples were Ki67- and 44.6% vs. 55.6% (P = .02) p53-positive, comparing the older and younger women. There was also decreased expression of E-cadherin (P = .002) and CK 7/8 (P = .005), but increased expression of bcl2 (P less than .001), CK14 (P = .03), and CK18 (P less than .001) in the older women.
The findings are counterintuitive to what might be expected commented Dr. Catherine Terret of Centre Léon Bérard, in Lyon, France.
"I think this is surprising for the clinician because my feeling is triple-negative breast cancer in the elderly is a very aggressive tumor," Dr. Terret, who was not involved in the study, said. "I’m really surprised [the] biologic results don’t go in the same way as my clinical opinion."
Dr. Cheung and Dr. Terret had no relevant financial disclosures.