Top Breast Cancer Research Findings for the Past Year

Debu Tripathy, MD

A new standard that recommends ovarian function suppression (OFS) therapy as a routine adjuvant treatment option for certain premenopausal women with higher risk, hormone receptor (HR)—positive breast cancer emerged as the most far-reaching medical oncology research finding in the field for 2014, according to Debu Tripathy, MD. Other noteworthy developments emanated from negative clinical trials and an early immunotherapy study.

These findings are among the 2014 highlights that Tripathy reviewed in an overview that was the annual feature of the Miami Breast Cancer Conference Feb. 26-March ¹. Tripathy, who serves as one of the directors of the conference, is a professor and chair of the Department of Breast Medical Oncology at The University of Texas MD Anderson Cancer Center in Houston.

In all, Tripathy selected 12 abstracts from the 2014 American Society of Clinical Oncology (ASCO) Annual Meeting in June and the 2014 San Antonio Breast Cancer Symposium (SABCS) in December to focus upon during his presentation (Table).

SOFT Trial Maps New Option

The findings with the most practice-changing potential are the SOFT trial results reported at SABCS, Tripathy said in an interview in advance of his presentation. For the past 15 years, tamoxifen has been the standard adjuvant hormonal treatment after surgery for premenopausal patients with HR-positive early breast cancer, and guidelines tend to recommend against routinely adding OFS therapy.¹

The SOFT investigators were seeking to determine whether adding OFS therapy to 5 years of either tamoxifen or exemestane reduced the risk of recurrence compared with tamoxifen alone for women with HR-positive breast cancer who either were premenopausal or remained so after receiving chemotherapy (Figure). OFS was achieved by choice of monthly injections of the gonadotropin-releasing hormonal agonist triptorelin, bilateral oophorectomy, or bilateral ovarian irradiation; 80.7% of those assigned to OFS during the trial received triptorelin.¹

Overall, the addition of OFS therapy did not result in a statistically significant advantage in disease-free survival (DFS) when outcomes for the more than 3000 women who participated in the trial were compared in the primary analysis for tamoxifen plus OFS versus tamoxifen alone. At a median follow-up of 5.6 years, the addition of OFS to tamoxi¬fen resulted in a DFS rate of 86.6% compared with 84.7% for tamoxifen alone (HR = .83; 95% CI, 0.66-1.04; P = .10).²

In subset analyses, however, more robust differences emerged. For participants who were premenopausal after prior chemotherapy (average age of 40 years), OFS therapy reduced the risk of recurrence by 22% when added to tamox¬ifen and by 35% when combined with exemestane.

Among the 350 women aged <35 in the overall study population, 94% of whom had received chemotherapy, the 5-year DFS rates were 83.4% (95% CI, 74.9-89.3), 78.9% (95% CI, 69.8-85.5), and 67.7% (95% CI, 57.3-76.0), respectively, for patients treated with exemestane plus OFS, tamoxifen plus OFS, and tamoxifen alone. “The patients who seemed to benefit not only from the addition of ovarian blockade but also from the use of an aro¬matase inhibitor instead of tamoxifen were patients who had positive nodes, patients who received chemotherapy, and patients who were under the age of 35,” noted Tripathy. “All of these subgroups, essentially, were higher-risk patients.

“Now, it’s always difficult to interpret a study and make recommendations based on such subset analyses,” he continued. “But these findings have been shown in other studies of smaller size that have ovarian ablation as an additional therapy, particularly for younger patients under the age of 35.”

As a result, Tripathy said, “ovarian suppression with an aromatase inhibitor may actually be the preferred therapy” for patients who are node-positive, getting chemotherapy, are premenopausal and remain premenopausal, and for patients under the age of 35. In contrast, patients not receiving che¬motherapy had excellent outcomes with tamoxifen alone, with 98.6% remaining free of recurrence and 99.2% alive at 5 years.

The decision should still be made on a case-by-case basis, he added, noting that OFS therapy comes with more side effects. The most common adverse events of all grades for patients who received tamoxifen plus OFS compared with tamoxifen alone were hot flashes (93.4% vs 79.8%), depres¬sion (51.9% vs 46.6%), sweating (61.8% vs 48.3%), and insomnia (57.2% vs 46.3%).

Compelling Signals From Negative Trials

Tripathy’s list of noteworthy studies includes two trials in which researchers did not obtain the desired outcomes: (1) the ALTTO trial that examined the addition of lapatinib to trastuzumab for the adjuvant treatment of women with early breast cancer; and (2) the FERGI study that evaluated the novel PI3K inhibitor pictilisib in estrogen receptor—positive metastatic breast cancer resistant to aromatase inhibitor therapy.

The phase III ALTTO trial, which enrolled more than 8000 women in 44 countries, demonstrated that treat¬ment with lapatinib plus trastuzumab, either sequentially or concurrently, was associated with a high DFS rate but that combining the drugs did not produce a statistically significant advantage over trastuzumab alone. All patients also received chemotherapy.

At a median follow-up of 4.5 years, the DFS rates were 86% for patients who received trastuzumab alone; 88% for participants treated with trastuzumab and lapatinib concurrently; and 87% for patients who received trastuzumab followed by lapatinib.³

The results proved to be a disappointment after the Neo-ALTTO study,⁴ released in December 2013, showed a higher pathological compete response with the combination.

“We were all very excited by the neoadjuvant data where the pathological response rate was significantly improved with the addition of lapatinib to trastuzumab, given with chemotherapy,” said Tripathy. “We assumed that this would translate into an improvement when we tested this combina¬tion in the adjuvant setting.”

“Now this raises the whole question as to whether this neoadjuvant model is helpful to us in predicting what regimens are going to be successful in the adjuvant setting,” added Tripathy. “So that was an important abstract. This also confirms the need to analyze neoadjuvant results in the context of defined biological subsets.”

In the phase II FERGI trial, the combination of pictilisib plus fulvestrant did not demonstrate a statistically significant improvement in median progression-free survival (PFS) compared with fulvestrant alone (6.6 months vs 5.1 months, respective¬ly).5 Although aberrations in the PI3K pathway are frequently observed in ER-positive breast cancer, PIK3CA mutation status had no effect on PFS among participants in the trial. However, there was evidence of antitumor activity in a subset of patients with ER-positive, progesterone recep¬tor—negative disease; the PFS for this group was 7.4 months in the combination arm versus 3.7 months with fulvestrant alone (P = .002).

“We need to understand a little bit better how these drugs work as we figure out how to develop them in the clinic,” commented Tripathy.

PD-1 Buzz Hits Breast Cancer

The PD-1 antibody pembrolizumab, which gained FDA approval last year in metastatic melanoma and has been designated as a breakthrough therapy in non—small cell lung cancer, dem¬onstrated that the immune checkpoint blockade strategy of targeting PD-1 may have a place in breast cancer treatment.

In the KEYNOTE-012 study, pembrolizumab demonstrated an 18.5% overall response rate among patients with meta¬static triple-negative breast cancer whose tumors tested positive for expression of the PD-1 ligand, PD-L1. Partici¬pants in the phase IB trial had been heavily pretreated, with 21.9% having received ≥5 lines of therapy. Additionally, 87.5% of patients had received neoadjuvant or adjuvant therapy.⁶

“We know that patients who have triple-negative cancers do seem to have a higher immunogenicity,” said Tripathy. “These tumors are more active and visible by the immune system—possibly because they tend to carry more mutations and therefore have altered epitopes that are more immunogenic. So the newer generation of so-called checkpoints that augment the immune system may be particularly active in triple-negative cancers, which is an area where there is a great unmet need.

“This is really the first demonstration of any single biologic agent that we have today with activity in triple-negative breast cancers, and the first immunotherapy to show this kind of effect,” Tripathy noted

Table: Dr Tripathy’s Picks

Debu Tripathy, MD, has selected these abstracts from among the hundreds of papers and posters presented at the 2014 American Society of Clinical Oncology (ASCO) Annual Meeting and the 2014 San Antonio Breast Cancer Symposium (SABCS) as among last year’s most noteworthy research findings.

For ASCO abstracts, visit http://goo.gl/bE6s0n. For SABCS, visit http://goo.gl/5NPVjw.

• ALTTO Trial—Compares sequential and combination lapatinib, trastuzumab. The negative findings were somewhat surprising given the impact that the combination had in the neoadjuvant setting on higher complete pathological complete response rates compared with either of the single agents. (Piccart- Gebhart MJ et al. ASCO; abstr LBA 4)
• TEXT/SOFT Trials—The joint analysis comparing adjuvant exemestane with tamoxifen along with ovarian suppression in premenopausal women with early stage breast cancer showed that exemestane was superior with an absolute 5-year disease-free survival of slightly under 4%. (Pagani O et al. ASCO; abstr LBA1)
• SOFT Update—Update of the SOFT trial with data from the tamoxifen-only arm showed overall negative results from the addition of ovarian suppression to hormonal therapy. However, in high-risk subsets, there was a survival benefit, particularly when exemestane was used. (Frances PA et al. SABCS; abstr S3-08)
• POEMS Trial—LHRH analogue treatment during chemotherapy. This phase III trial showed improvement not only in maintaining menses, but actual fertility and childbirth in women undergoing chemotherapy with the use of gonadotropin analogues. Surprisingly, survival was improved, but with such a small number of deaths, this could have been due to chance, and needs further follow up and confirmatory studies. (Moore H et al. ASCO; abstr LBA505)
• OPTIMIZE-2—Trial showed that decreasing zoledronate in the second year to once every 12 weeks (instead of monthly) for the treatment of bone metastases did not compromise the benefit in terms of bone events, and no osteonecrosis of the jaw was seen at the longer frequency (compared with 2 monthly). (Hortobagyi G et al. ASCO; abstr LBA9500).
• GeparSepto—Study showed a superiority of nabpaclitaxel over paclitaxel with a higher complete pathological response rate when used in the neoadjuvant setting with trastuzumab/pertuzumab (if HER2+), then followed by epirubicin and cyclophosphamide. This was most noted in the triple-negative subgroup, and accompanied by more peripheral neuropathy with nab-paclitaxel. (Untch M et al. SABCS; abstr S2-07)
• OPPORTUNE—A “window of opportunity” study examining the alpha-selective PI3 kinase inhibitor pictilisib (GDC-0941) in the preoperative setting evaluated 2 weeks of exposure. A significant drop in Ki67, the primary endpoint, was seen with the addition of pictilisib to anastrozole. (Schmid P et al. SABCS; abstr S2-03)
• FERGI—In the metastatic setting, the phase II FERGI trial showed equivalent PFS when pictilisib was added to fulvestrant for aromatase inhibitor-resistant breast cancer, but yielded a significant benefit in the exploratory subset of ER+/PR+ cases. There was no difference seen among those with activating PIK3CA mutations vs wild-type. (Krop I et al. SABCS; abstr S2-02)
• FIRST—Phase II trial showed a borderline improvement in PFS with first-line fulvestrant at 500-mg dosing over anastrozole, but follow-up was interrupted and results from the phase III Falcon trial are awaited (Robertson JFR et al. SABCS; abstr S6-04)
• TNT—The trial compared carboplatin to docetaxel in the first-line setting for triple negative breast cancer and showed equivalent response rate overall, but a significantly higher response rate with carboplatin in cases with BRCA mutation. (Tutt A et al. SABCS; abstr S3-01)
• KEYNOTE-012—The trial tested the PD-1 checkpoint- inhibiting antibody pembrolizumab (MK-3745) in heavily pretreated triple-negative breast cancer and showed a response in 5 of 27 cases (18.5%), with 3 responses out to 48 weeks or longer. (Nanda R et al. SABCS; abstr S1-09)
• BOLERO-1—This trial tested the addition of the mTOR inhibitor everolimus to paclitaxel plus trastuzumab for first-line HER2+ metastatic breast cancer, and showed no difference in the primary endpoint of PFS, but did show a significant benefit in the subset of patients with hormone receptor—negative cancers. (Hurvitz SA et al. SABCS; abstr. S6-01)