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Annual Meeting Proceedings Part 1 - American Society of Clinical ...

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508 <strong>Clinical</strong> Science Symposium, Sat, 1:15 PM-2:45 PM<br />

A phase I/IB dose-escalation study <strong>of</strong> BEZ235 in combination with<br />

trastuzumab in patients with PI3-kinase or PTEN altered HER2� metastatic<br />

breast cancer. Presenting Author: Ian E. Krop, Dana-Farber Cancer<br />

Institute, Boston, MA<br />

Background: Alterations in the PI3K/AKT/mTOR pathway have been implicated<br />

in resistance to trastuzumab (T) in HER2� breast cancer. BEZ235, a<br />

potent oral dual PI3K/mTORC1/2 inhibitor, has demonstrated growth<br />

inhibition and apoptosis in HER2� breast cancer models, including those<br />

harboring PI3K pathway alterations, and with T resistance. In a Phase I<br />

study, BEZ235 was well tolerated as a single agent in pts with advanced<br />

solid tumors. The aim <strong>of</strong> this study was to determine the MTD <strong>of</strong> BEZ235 in<br />

combination with T in pts with T-resistant HER2� metastatic breast cancer<br />

(mBC) with alterations <strong>of</strong> the PI3K pathway. Methods: Pts with T-resistant<br />

HER2� mBC (i.e. disease progression during adjuvant therapy or metastatic<br />

disease on therapy with T) received oral BEZ235 daily, with weekly T<br />

(2 mg/kg). Pts were eligible for enrollment if a tumor sample was<br />

demonstrated to contain a molecular alteration <strong>of</strong> PIK3CA and/or PTEN.<br />

Dose escalation was guided by a Bayesian logistic regression model with<br />

overdose control. Results: As <strong>of</strong> 23 Sep 2011, 15 <strong>of</strong> the 19 enrolled pts<br />

were evaluable for dose escalation analysis. BEZ235 was evaluated at 3<br />

dose levels: (1) 400 mg/day (3 pts); (2) 600 mg/day (6 pts); (3) 800<br />

mg/day (10 pts), administered either in capsule form (400 mg) or in sachet<br />

form (600 mg and 800 mg). The MTD <strong>of</strong> BEZ235 in combination with T<br />

was estimated to be 600 mg/day. Observed DLTs were G3 nausea at 600<br />

mg/day (1 pt), and G3 nausea, G3 fatigue and G3 skin rash (1 pt each) at<br />

800 mg/day. The most frequent G3/4 adverse events (CTCAE v3.0)<br />

suspected to be related to study treatment were diarrhea (4 pts) and nausea<br />

(2 pts). No deaths related to study treatment occurred. 1 pt with lung and<br />

brain metastases had a partial response. 4 pts had disease stabilization for<br />

�4 cycles (16 weeks), including 1 pt with liver metastases, in whom<br />

BEZ235/T treatment resulted in disease stabilization for more than 21<br />

cycles (84 weeks). Conclusions: BEZ235in combination with T demonstrated<br />

an acceptable safety pr<strong>of</strong>ile in pts with HER2� mBC and PI3K<br />

pathway alterations. Following the Bayesian model recommendation, the<br />

MTD for BEZ235 in combination with T was estimated to be 600 mg/day.<br />

The safety expansion arm is ongoing at the MTD.<br />

510 <strong>Clinical</strong> Science Symposium, Sat, 1:15 PM-2:45 PM<br />

SU2C phase Ib study <strong>of</strong> pan-PI3K inhibitor BKM120 with letrozole in ER�/<br />

HER2- metastatic breast cancer (MBC). Presenting Author: Ingrid A. Mayer,<br />

Vanderbilt-Ingram Cancer Center, Nashville, TN<br />

Background: Mutations in PIK3CA, the gene encoding the p110a subunit <strong>of</strong><br />

PI3K, have been associated with antiestrogen resistance in ER� BC. In general,<br />

antiestrogen-resistant cancers retain ER and responsiveness to estradiol. This<br />

suggests that treatment <strong>of</strong> ER�/PI3K mutant BC should include PI3K inhibitors<br />

plus antiestrogens. Methods: We conducted a phase Ib trial <strong>of</strong> letrozole (2.5<br />

mg/d) with the pan-PI3K inhibitor BKM120 in post-menopausal patients (pts)<br />

with ER�/HER2 MBC. BKM120 (100 mg/d) was given continuously (Arm A) or<br />

intermittently (5 on/2 <strong>of</strong>f days; Arm B). Upon toxicity, BKM120 was reduced to<br />

80 and 60 mg/d. Treatment continued until unacceptable toxicity or disease<br />

progression. Disease was assessed every 2 months. FDG-PET was done at<br />

baseline and at 2 weeks in all pts in Arm A. Results: Fifty-one pts were accrued;<br />

49 had progressed on an AI previously. Median age was 56 years (range 34-77);<br />

95% had bone and 70% visceral metastases. Toxicities and outcomes are<br />

summarized in the table. The only DLT* in Arm A and B were transaminitis and<br />

depression, respectively; both at 100 mg. Over 50% <strong>of</strong> Arm A pts had �25%<br />

reduction in their peak SUV at the 2-week FDG-PET. Pts who did not exhibit a<br />

metabolic response by FDG-PET progressed rapidly on therapy. Three pts in Arm<br />

A had a PI3K mutation; one <strong>of</strong> them has had stable disease on treatment for �12<br />

months. Conclusions: The combination <strong>of</strong> letrozole/ BKM120 is safe in pts with<br />

AI-refractory ER�/HER2 MBC. Arm B is ongoing and will be updated at the<br />

meeting. All tumor biopsies will be analyzed for PI3K pathway alterations.<br />

FDG-PET at 2 weeks appears to be a useful pharmacodynamic biomarker <strong>of</strong> PI3K<br />

pathway inhibition in most patients. Its value in predicting treatment response<br />

remains to be determined.<br />

ArmA(N�20) Arm B (N�31)<br />

Grade (%)<br />

Grade (%)<br />

Toxicity<br />

1 2 3 Total 1 2 3 Total<br />

Hyperglycemia 50 10 10 70 16 3 0 19<br />

Nausea 55 10 0 65 12 0 0 12<br />

Fatigue 25 40 5 70 9 3 0 12<br />

Transaminitis 35 25 15* 75 16 6 6 16<br />

Diarrhea 40 10 0 50 19 0 0 19<br />

Anxiety 25 15 5 45 3 3 0 6<br />

Depression 15 35 5 55 3 6 3* 12<br />

Rash 30 0 5 35 3 0 0 3<br />

Outcomes Arm A (N�20) Arm B (N�31)<br />

CR 1 0<br />

PR 1 0<br />

SD >4 months 9 4<br />

PD 7 8<br />

Non-evaluable 2 5<br />

Still on treatment 1 17<br />

Median TTP (months) 4 (2-11) N/A<br />

Discontinued due to toxicity 6 3<br />

Treatment > 8 weeks without interruption 17 N/A<br />

Breast Cancer—HER2/ER<br />

509 <strong>Clinical</strong> Science Symposium, Sat, 1:15 PM-2:45 PM<br />

PI3K pathway (PI3Kp) dysregulation and response to pan-PI3K/AKT/mTOR/<br />

dual PI3K-mTOR inhibitors (PI3Kpi) in metastatic breast cancer (MBC)<br />

patients (pts). Presenting Author: Mafalda Oliveira, Breast Cancer Group,<br />

Vall d’Hebron University Hospital, Barcelona, Spain<br />

Background: The role <strong>of</strong> PI3Kp dysregulation as a predictor <strong>of</strong> sensitivity to<br />

PI3Kpi is unclear. We aimed to evaluate the efficacy <strong>of</strong> PI3Kpi in two<br />

cohorts <strong>of</strong> MBC pts with assessable PI3Kp status. Methods: MBC pts<br />

treated in �3rd line with PI3Kpi were reviewed. PI3Kp status: (a) No<br />

dysregulation: PIK3CA wt and PTEN normal; (b) PI3Kp dysregulation:<br />

PIK3CA mutation (PIK3CAmut) or PTEN low (HScore�50). Cohort A: pts<br />

treated with single agent PI3Kpi. Cohort B: pts treated with PI3Kpi in<br />

combination with hormonal therapy (HT), chemotherapy (CT) and/or<br />

trastuzumab (T). Results: Out <strong>of</strong> 232 MBC pts screened for PI3Kp<br />

alterations from Sep09 to Sep11, 32 were treated with PI3Kpi. Cohort A<br />

(n�17): HR�/HER2- 88%, HER2� 6%, triple negative 6%; median age<br />

43, median MBC lines 4 (2-9); PIK3CAmut in 10/17 (58.8%; 6 exon9, 4<br />

exon20), PTEN low 3/17 (17.6%), 1 pt both; PI3Kp dysregulation 12/17<br />

pts. Cohort B (n�15): HR�/HER2- 40%, HER2� 60%; median age 49,<br />

median MBC lines 4 (2-13); PIK3CAmut 3/13 assessable (23.1%; all<br />

exon20), PTEN low 6/15 (40%), 1 pt both; PI3Kp dysregulation 8/15 pts.<br />

Time to progression to PI3Kpi (TTP), overall survival from MBC diagnosis<br />

(OSMBC) and OS from PI3Kpi beginning (OSPI3Kpi), according to PIK3CA<br />

status and PI3Kp dysregulation, are shown. No differences were found<br />

according to PTEN status. Conclusions: These results suggest that the best<br />

outcomes with PI3Kpi in PIK3CAmut MBC pts occur when they are used in<br />

combination with HT/CT/T. Activity <strong>of</strong> non selective PI3Kpi used as single<br />

agents seems to be limited, making results from prospective trials with<br />

selective PI3K� inhibitors and PI3Kpi in combinations eagerly awaited.<br />

Months<br />

Median<br />

(95%CI)<br />

Cohort A<br />

n�17<br />

TTP<br />

OSMBC<br />

OSPI3Ki<br />

Cohort B<br />

n�15<br />

TTP<br />

OSMBC<br />

OSPI3Ki<br />

PIK3CA PI3Kp dysregulation<br />

WT Mut p No Yes p<br />

n�7 n�10 n�5 n�12<br />

7.4<br />

(3.5-11.2)<br />

95<br />

(0-206.9)<br />

NR<br />

1.4<br />

(0-3.6)<br />

47.1<br />

(12.4-81.9)<br />

8.5<br />

(2.8-14.2)<br />

0.026<br />

0.217<br />

0.048<br />

4.9<br />

(1.5-8.2)<br />

95<br />

(-)<br />

NR<br />

1.4<br />

(0-3.3)<br />

47.1<br />

(13.6-80.7)<br />

5.7<br />

(1.8-9.5)<br />

n�10 n�3 n�7 n�8<br />

3.6 (1.2-6.1)<br />

NR<br />

NR<br />

8.4 (-)<br />

NR<br />

NR<br />

0.053<br />

0.212<br />

0.223<br />

3.6 (0.7-6.6)<br />

55.7 (53.5-57.8)<br />

5.9 (2.6-9.2)<br />

3.7 (2.2-5.2)<br />

NR<br />

NR<br />

0.092<br />

0.097<br />

0.039<br />

0.451<br />

0.216<br />

0.306<br />

511 Poster Discussion Session (Board #1), Sat, 1:15 PM-5:15 PM and<br />

4:45 PM-5:45 PM<br />

Randomized trial <strong>of</strong> marker-directed versus standard schedule zoledronic<br />

acid for bone metastases from breast cancer. Presenting Author: Robert<br />

Edward Coleman, CR-UK/YCR Sheffield Cancer Research Centre, Sheffield,<br />

United Kingdom<br />

Background: Zoledronic acid (ZOL) reduces skeletal morbidity associated<br />

with metastatic bone disease by 30-50%. Current recommendations are for<br />

indefinite administration <strong>of</strong> intravenous 3-4 weekly (w) ZOL 4mg. Over<br />

recent years it has become clear that the risk <strong>of</strong> skeletal morbidity is related<br />

to the rate <strong>of</strong> bone resorption. We have compared a marker directed<br />

schedule <strong>of</strong> ZOL (M-ZOL), using measurements <strong>of</strong> urinary n-telopeptide <strong>of</strong><br />

type I collagen (NTX), to a standard treatment schedule (S-ZOL) in patients<br />

with bone metastases from breast cancer. Methods: The primary endpoint<br />

was skeletal related events (SRE). A non-inferiority study was designed with<br />

80% power and (one-sided) 5% alpha to demonstrate that M-ZOL retained<br />

67% <strong>of</strong> the efficacy <strong>of</strong> S-ZOL. This required 1500 patients, assuming a<br />

SRE rate <strong>of</strong> 0.7/year. Following minimisation for known prognostic factors,<br />

patients were randomised to receive S-ZOL 3-4 w or M-ZOL (15-16w; 8-9 w<br />

or 3-4w if NTX levels were �50, 50-100, �100 nmol/mmol creatinine<br />

respectively), with the schedule adjusted according to NTX measured every<br />

16 weeks. The study duration was 24 months. Results: Due to lower than<br />

expected recruitment, the study closed in 2009 following recruitment <strong>of</strong><br />

289 patients. 90% <strong>of</strong> patients had received �4 cycles <strong>of</strong> ZOL or<br />

pamidronate prior to randomisation. The median number <strong>of</strong> ZOL infusions<br />

administered to S-ZOL patients was �2x that received on M-ZOL. 46<br />

(32%) S-ZOL and 55 (38%) M-ZOL patients experienced an SRE. The<br />

numbers <strong>of</strong> SRE were 94 and 138 in the S-ZOL and M-ZOL arms, with the<br />

excess in SRE being largely due to more patients on M-ZOL experiencing<br />

�2 SRE. Multivariate analysis adjusting for key minimisation factors and<br />

baseline NTX for all SRE showed a hazard ratio for M-ZOL vs. S-ZOL <strong>of</strong> 1.41<br />

(90%CI 0.98-2.02, p�.12). NTX levels were significantly higher at all time<br />

points in the M-ZOL treated patients. Osteonecrosis <strong>of</strong> the jaw was<br />

uncommon with 3 cases with S-ZOL and 1 with M-ZOL. Conclusions: The<br />

study is underpowered to demonstrate non-inferiority in SRE outcome<br />

between the treatment strategies. However, the results suggest that the<br />

adjustment <strong>of</strong> ZOL schedule based on NTX values alone may represent<br />

sub-optimal management.<br />

Visit abstract.asco.org and search by abstract for the full list <strong>of</strong> abstract authors and their disclosure information.<br />

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