Citations

LBA1 Background: Five years of aromatase inhibitor (AI) therapy either as up-front treatment or after 2-5 years of tamoxifen has become the standard of care for postmenopausal women with hormone receptor positive early breast cancer. Extending treatment with an AI to 10 years may further reduce the risk of breast cancer recurrence. Methods: We conducted a double-blind, placebo-controlled trial (Canadian Cancer Trials Group MA.17R) to test the efficacy of extending AI treatment for an additional five years using letrozole. The primary endpoint was disease-free survival. Results: A total of 1,918 women with early stage breast cancer were enrolled (median follow-up 75 months, 6.3 years). A total of 165 disease-free survival (DFS) events (67 on letrozole and 98 on placebo) occurred, of which 42 versus 53 were distant recurrences on letrozole and placebo, respectively. There were 200 deaths (100 in each treatment group). The 5 year DFS was respectively 95% for patients receiving letrozole versus 91% for those on placebo (HR 0.66; P = 0.01) from a two-sided log-rank test stratified by nodal status, prior adjuvant chemotherapy, interval between last dose of AI therapy and randomization, and duration of prior tamoxifen at randomization. The 5 year overall survival was respectively 93% for subjects on letrozole and 94% on placebo with a HR of 0.97 (P = 0.83). The annual incidence rate of contralateral breast cancer was 0.21% for subjects on letrozole versus 0.49% on placebo (P = 0.007). Conclusions: Compared to 5 years of AI treatment as initial therapy or preceded by 2-5 years of tamoxifen, extending AI treatment to 10 years significantly improves disease-free survival. Further analyses will provide a comprehensive picture of toxicities and QOL. Clinical trial information: NCT00754845.

2 Background: The MA.17 trial demonstrated that extended adjuvant endocrine therapy with letrozole after 5-y of tamoxifen markedly reduced the risk of recurrence in women with ER+ early stage breast cancer. This trial provides an opportunity to assess the ability of biomarkers to predict late recurrences in ER+ breast cancer. The Breast Cancer Index (BCI), a continuous risk index based on the combination of HOXB13:IL17BR (H:I) and the molecular grade index (MGI), estimates the individual risk of recurrence in ER+ breast cancer patients. In this study, the prognostic utility of BCI to predict late recurrences was examined. Methods: FFPE tumor blocks were collected from patients who experienced a breast cancer recurrence up to unblinding of MA.17. Controls were matched 2:1 for age, tumor size, nodal status and prior chemotherapy, and were disease free for longer than cases. All cases were reviewed for standard histopathology and evaluated using the real-time RT-PCR BCI assay. Results: Patient characteristics for the case-control study were similar to that from the overall study. Characteristics for cases (N=83) and controls (N=166) were not significantly different except for treatment. A higher percentage of controls compared to cases tended to be categorized as low risk by BCI (58% vs 43%), while a lower percentage of controls than cases tended to be categorized as high risk by BCI (34% vs 24%). In univariate analysis, treatment, BCI, H:I and HOXB13, but not tumor grade or MGI, were significant predictors of late recurrence. After adjusting for standard variables (age, tumor grade and treatment), BCI (OR 2.37; P=0.03), H:I (OR 2.55; P=0.04) and HOXB13 (OR 1.35; P=0.02) remained significant predictors of recurrence. HOXB13 expression at diagnosis predicted patient benefit from extended endocrine therapy with letrozole. Conclusions: In this case-controlled study, the data demonstrate that BCI is a significant predictor of late recurrences in ER+ patients following 5-y of tamoxifen. The prognostic performance of BCI to predict late recurrences was largely dependent on HOXB13 expression. The integration of H:I and MGI within BCI provides prognostic utility for both early and late recurrences.

LBA504 Background: Limited efficacy and serious toxicities have limited uptake of tamoxifen or raloxifene as preventatives of breast cancer. Aromatase inhibitors (AIs) prevent contralateral breast cancers more than tamoxifen in adjuvant trials and have fewer serious side effects. This is the first report of an AI used in primary prevention. Methods: NCIC CTG MAP.3 is a randomized trial designed to detect a 65% reduction in annual incidence of invasive breast cancer (IBC) on exemestane (E) versus placebo (P). Eligible postmenopausal women had ≥ one of the following risk factors: Gail score >1.66%, prior ADH, ALH, LCIS or DCIS with mastectomy, age over 60. Health-related and menopause-specific quality of life (QOL) were assessed by SF-36 and MENQOL questionnaires. Results: From 2004-2010, 4,560 women were randomized: age 62.5 yrs (37-90); Gail Score 2.3 % (0.6-21); BMI 28.0 kg/m2 (15.9-65.4). Risk factors included: age >60 yrs (49%); Gail score >1.66 (40%); and prior ADH, ALH, LCIS or DCIS with mastectomy (11%). At median follow-up of 35 months there were 11 IBCs on E and 32 on P (annual incidence 0.19% vs 0.55%; HR= 0.35, 95% CI 0.18-0.70, p = 0.002); ductal (10E/27P), lobular (1E/5P). Most tumors were ER positive (7E/27P); Her2/neu negative (10E/26P); TNM stage T1 (8E/28P), N0 (7E/22P), M0 (11E/30P). E was superior in all subgroups: by Gail score, age, BMI, prior LCIS and DCIS. The annual incidence rate of IBC or DCIS was 0.35% E and 0.77% P (HR=0.47;95% CI 0.27-0.79; p = 0.004) based on 64 IBCs or DCISs (20E/44P). Clinical bone fractures, osteoporosis, hypercholesterolemia or cardiovascular events were equal in both arms. No clinically meaningful differences in QOL were detected. Conclusions: Exemestane significantly reduced invasive and pre-invasive breast cancers in postmenopausal women at increased risk for breast cancer with no serious toxicities. Exemestane should be considered a new option for primary prevention of breast cancer. Supported by the Canadian Cancer Society; Pfizer Inc. PEG supported in part by Avon Foundation.

Abstract Background: MA17 showed that adjuvant letrozole after 5 years of tamoxifen markedly reduced the risk of recurrence in women with ER+ early stage breast cancer and improved overall survival in women presenting with node +ve disease. Most trials of early adjuvant aromatase inhibitor therapy required women to be postmenopausal at diagnosis to be eligible. We report here on a subset of women in the MA17 trial who were premenopausal at initial diagnosis and in whom subsequent menopause, prior to randomization, may have influenced their outcome on extended adjuvant letrozole.Methods: Women randomized to MA17 were divided into 2 groups: 1) pre-menopausal (< 50 years of age but underwent bilateral oophorectomy at time when tamoxifen treatment started or < 50 years of age at the start of tamoxifen treatment but became amenorrheic during adjuvant chemotherapy or tamoxifen treatment) and 2) post-menopausal. Disease-free survival (DFS) from time of randomization for women in these two groups were summarized by Kaplan-Meier curves and compared based on log-rank test and Cox model.Results: 889 women were identified as premenopausal and 4,277 as postmenopausal. Treatment, age, race, duration of tamoxifen, prior adjuvant chemotherapy, and mastectomy were independently associated with menopausal status on multivariate analysis. The interaction between treatment and menopausal status was statistically significant for DFS (p=0.02), indicating that women diagnosed with pre-menopausal breast cancer had significantly greater benefit (Hazard ratio=0.25, 95% CI: 0.12-0.51) with letrozole treatment in terms of DFS than those with post-menopausal status (hazard ratio=0.69 with 95% CI from 0.52 to 0.91). In comparison with women treated with placebo, pre-menopausal women on letrozole had a significantly higher incidence of arthralgia (24 vs. 16%; p=0.004) but a lower incidence of vaginal bleeding (10 vs. 16%; p=0.01). Compared with placebo post-menopausal women receiving letrozole had a higher incidence of hot flashes/flashes (55 vs. 50%; p=0.001), arthralgia (25 vs. 21%; p=0.002), myalgia (15 vs. 12%; p=0.007) and alopecia (5 vs. 3%; p=0.003).Conclusions: Letrozole after tamoxifen was more effective in improving DFS in women who were premenopausal at primary diagnosis than those who were postmenopausal. Letrozole was well tolerated in premenopausal women. These data indicate that women who are premenopausal at the time of diagnosis but become postmenopausal anytime before, or during, adjuvant tamoxifen should be considered for extended adjuvant therapy with letrozole. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 13.

Abstract Phase II trials are screening trials that seek to identify agents with sufficient activity to continue development and those for which further evaluation should be halted. Although definitive phase III trials use progression-free or overall survival to confirm clinical benefit, earlier endpoints are preferable for phase II trials. Traditionally, tumor shrinkage of a predetermined degree (response) has been used as a surrogate of eventual survival benefit based on the observation that high response rates (RR), and particularly complete responses, in the phase II setting resulted in survival benefit in subsequent phase III trials. Recently, some molecularly targeted agents have shown survival and clinical benefit despite very modest RRs in early clinical trials. These observations provide a major conundrum, with concerns of inappropriate termination of development for active agents with low RRs being balanced by concerns of inactive agents being taken to late-phase development with resultant increases in the failure rate of phase III trials. Numerous alternate or complementary endpoints have been explored, incorporating multinomial endpoints (including progression and response), progression-free survival, biomarkers, and, more recently, evaluation of tumor size as a continuous variable. In this review, we discuss the current status of phase II endpoints and present retrospective analyses of two international gastrointestinal cancer studies showing the potential utility of one novel approach. Alternate endpoints, although promising, require additional evaluation and prospective validation before their use as a primary endpoint for phase II trials.

Purpose National Cancer Institute of Canada Clinical Trials Group trial MA.17 randomly assigned 5,187 postmenopausal, hormone-receptor–positive patients with early breast cancer who completed 5 years of tamoxifen to receive either letrozole or placebo. At 30 months median follow-up, letrozole significantly improved disease-free survival (DFS) in all patients and overall survival (OS) in node-positive patients. Breast cancer incidence increases with age and more than 1,300 women age 70 years or older were enrolled onto MA.17, making it ideal to explore the benefits, toxicities, and quality of life (QOL) impact of letrozole on older women. Patients and Methods In this study, 5,169 randomly assigned patients were divided into three age groups: younger than 60 years (n = 2,152), 60 to 69 years (n = 1,694), and ≥ 70 years (n = 1,323). Log-rank test was used to compare differences in DFS, distant-disease–free survival, and OS between age and treatment groups, and Cox models were used to estimate hazard ratios and associated 95% CIs. QOL was measured using the Medical Outcomes Short Form-36 and the Menopause-Specific Quality-of-Life questionnaire. Results At 4 years, DFS demonstrated statistically significant differences favoring letrozole only in patients age younger than 60 years (hazard ratio = 0.46; P = .0004); there was no interaction between age and treatment, indicating a similar effect of letrozole among all age groups. There was no difference in toxicity or QOL at 24 months among letrozole- and placebo-treated patients age ≥ 70 years. Conclusion Healthy patients age 70 years and older completing 5 years of tamoxifen should be considered for extended adjuvant therapy with letrozole.

Purpose The National Cancer Institute of Canada Clinical Trials Group MA.17 trial examined the efficacy of letrozole (LET) started within 3 months of 5 years of adjuvant tamoxifen in postmenopausal hormone receptor–positive early-stage breast cancer. When the trial was unblinded, patients who received placebo (PLAC) were offered LET. Patients and Methods This cohort analysis describes the outcomes of women assigned PLAC at the initial random assignment after unblinding. Efficacy outcomes of women who chose LET (PLAC-LET group) were compared with those who did not (PLAC-PLAC group) by the hazard ratios and by P values calculated from Cox models that adjusted for imbalances between the groups. Toxicity analyses included only events that occurred after unblinding. Results There were 1,579 women in the PLAC-LET group (median time from tamoxifen, 2.8 years) and 804 in the PLAC-PLAC group. Patients in the PLAC-LET group were younger; had a better performance status; and were more likely to have had node-positive disease, axillary dissection, and adjuvant chemotherapy than those in the PLAC-PLAC group. At a median follow-up of 5.3 years, disease-free survival (DFS; adjusted hazard ratio [HR], 0.37; 95% CI, 0.23 to 0.61; P < .0001) and distant DFS (HR, 0.39; 95% CI, 0.20 to 0.74; P = .004) were superior in the PLAC-LET group. More self-reported new diagnoses of osteoporosis and significantly more clinical fractures occurred in the women who took LET (5.2% v 3.1%, P = .02). Conclusion Interpretation of this cohort analysis suggests that LET improves DFS and distant DFS even when there has been a substantial period of time since the discontinuation of prior adjuvant tamoxifen.

Purpose Controversy exists regarding estrogen (ER) and progesterone (PgR) receptor expression on efficacy of adjuvant endocrine therapy. In the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial, the benefit of anastrozole over tamoxifen was substantially greater in ER+/PgR–than ER+/PgR+ tumors. In BIG 1-98 (Breast International Group), the benefits of letrozole over tamoxifen were the same in ER+ tumors irrespective of PgR. MA.17 randomized postmenopausal women after 5 years of tamoxifen, to letrozole or placebo. We present outcomes according to tumor receptor status. Patients and Methods Disease-free survival (DFS) and other outcomes were assessed in subgroups by ER and PgR status using Cox's proportional hazards model, adjusting for nodal status and prior adjuvant chemotherapy. Results The DFS hazard ratio (HR) for letrozole versus placebo in ER+/PgR+ tumors (N = 3,809) was 0.49 (95% CI, 0.36 to 0.67) versus 1.21 (95% CI, 0.63 to 2.34) in ER+/PgR–tumors (n = 636). ER+/PgR+ letrozole patients experienced significant benefit in distant DFS (DDFS; HR = 0.53; 95% CI, 0.35 to 0.80) and overall survival (OS; HR = 0.58; 95% CI, 0.37 to 0.90). A statistically significant difference in treatment effect between ER+/PgR+ and ER+/PgR–subgroups for DFS was observed (P = .02), but not for DDFS (P = .06) or OS (P = .09). Conclusion These results suggest greater benefit for letrozole in DFS, DDFS, and OS in patients with ER+/PgR+ tumors, implying greater activity of letrozole in tumors with a functional ER. However, because this is a subset analysis and receptors were not measured centrally, we caution against using these results for clinical decision making.