Exemestane Reduces the Risk of Breast Cancer Recurrence

SAN ANTONIO—Updated results from the Intergroup Exemestane Study of 4,740 breast cancer patients show adjuvant therapy with the aromatase inhibitor exemestane (Aromasin) after 2 to 3 years of tamoxifen can cut risk of recurrence by 30% for women with early-stage breast cancer receiving hormonal treatment. Patients who switched from tamoxifen to exemestane also had 54% greater odds of remaining free of contralateral breast cancer, principal investigator R. Charles Coombes, MD, PhD, said at the 27th Annual San Antonio Breast Cancer Symposium (abstract 3).

Risk of death from all causes also was lower with exemestane, but Dr. Coombes said this trend has not reached statistical significance, with a P value of .08 at a median of 37.4 months of follow-up.

"Exemestane seems better in all subsets of patients, apart from ER-negative patients," said Dr. Coombes, director of the Cancer Research UK Laboratories at the Imperial College of Medicine and Hammersmith and Charing Cross Hospitals, London. The issue is no longer whether to switch from tamoxifen, he said, but when and for how long to continue with the aromatase inhibitor.

The trial randomized patients who had been successfully treated for estrogen-receptor (ER)-positive breast cancer after 2 to 3 years of adjuvant tamoxifen therapy. One group of 2,372 women stayed on tamoxifen for the remaining 2 to 3 years of hormonal treatment. The second cohort of 2,352 women converted to exemestane for the duration of therapy.

Fewer Deaths, Recurrences

The new data showed fewer breast cancer deaths with exemestane (95 vs 124 with tamoxifen). Another emerging trend, he said, was fewer deaths from cancers at other sites with exemestane (46 vs 69), mainly due to fewer deaths lung and uterine cancer and melanoma. Local recurrences were reduced with exemestane (43 vs 56), as were distant recurrences (150 vs 208) and primary contralateral breast cancers (12 vs 26).

Patients in the tamoxifen arm had significantly more thromboembolic events (69 vs 41 in the exemestane arm) and gynecologic symptoms (376 vs 301). As expected, incidences of musculoskeletal conditions such as arthritis, arthralgia, myalgia, and carpal tunnel syndrome were higher for women on exemestane.

Although the incidence of cardiac deaths was similar in both arms, myocardial infarctions were more than twice as common in the exemestane cohort (20 myocardial infarctions vs 8 in the tamoxifen arm). Dr. Coombes noted that all patients with myocardial infarction had at least one predisposing factor. "Tamoxifen may be exerting a preventive effect on myocardial infarction," he said.

The two hormonal agents received similar grades in a quality-of-life (QOL) report by Lesley Fallowfield, DPhil, who followed a subgroup of 582 Intergroup Exemestane Study patients (abstract 4). Dr. Fallowfield, professor of psycho-oncology, Brighton and Sussex Medical School, Sussex, UK, described quality of life as generally good in this interim report with follow-up of 24 months, with few differences in self-reports from these women.

Incidences of hot flashes, night sweats, severe weight gain, and loss of libido were similar between the two groups, she said. Severe vaginal discharge was significantly less often a problem with exemestane.

‘The Greater Issue’

The greater issue, she suggested, was loss of libido, which was a major problem for 32% to 35% of all patients. Similarly, she noted, about 20% of the total patient population complained of night sweats, and 25% experienced hot flashes. "Individual symptoms, especially vasomotor and sexual complaints, remain problematic with all endocrine therapy," she commented. "It behooves us to work energetically to overcome some of these problems."