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O04 - Molecular Pathology I (ID 126)
- Event: WCLC 2013
- Type: Oral Abstract Session
- Track: Pathology
- Presentations: 1
- Moderators:I.I. Wistuba, W.A. Cooper
- Coordinates: 10/28/2013, 10:30 - 12:00, Parkside Ballroom A, Level 1
O04.05 - Epidemiology of PI3K pathway alterations in patients with metastatic non-small cell lung cancer (NSCLC): findings from the international BASALT-1 study (ID 1810)
10:30 - 12:00 | Author(s): P. Roussou
Buparlisib (BKM120) is an oral PI3K inhibitor that inhibits all four isoforms of class I PI3K (α, β, γ, δ) and has demonstrated antiproliferative, proapoptotic, and antiangiogenic activity in multiple preclinical cancer models. NSCLC cell lines with PIK3CA mutations (muts) have demonstrated increased sensitivity to buparlisib in vitro. BASALT-1 – an ongoing, multicenter, open-label, two-stage Phase ll study (NCT01297491) – evaluates the safety and efficacy of single-agent buparlisib in patients (pts) with NSCLC and an activated PI3K pathway. Here we report data on the prevalence of PI3K pathway alterations in pts with squamous (sq) or non-squamous (non-sq) NSCLC prescreened for entry into BASALT-1.
Pts prescreened for BASALT-1 were ≥18 years of age with previously treated metastatic NSCLC of sq or non-sq histology. PI3K pathway activation (defined as PIK3CA mut and/or PTEN mut and/or PTEN negative [neg; <10% protein expression at 1+ by immunohistochemistry]) was measured in archival or newly acquired tumor tissue collected at prescreening. PIK3CA (exons 1, 5, 7, 9, and 20) and PTEN (exons 1–9) muts were detected primarily using Sanger sequencing in a centralized fashion. Local analysis was permitted at selected sites where a SnapShot approach was most commonly used.
As of April 10, 2013, 1183 pts had submitted tumor samples to be assayed (1179 tumors had known histology). PI3K pathway activation was detected in 16.0% of sq and 11.3% of non-sq tumors. In sq tumors (N=612), loss of PTEN protein expression (8.2%) was the most common single alteration observed, followed by PIK3CA mut only (3.1%) and PTEN mut only (2.9%). In non-sq tumors (N=567), PTEN mut only was the most common alteration (4.9%), followed by PIK3CA mut only (2.6%) and PTEN neg only (2.1%). Frequencies of co-existing genetic alterations were: PTEN mut + PTEN neg only (1.0% sq vs 0.4% non-sq), PIK3CA mut + PTEN neg only (0.7% sq vs 0.4% non-sq), PIK3CA mut + PTEN mut only (0% sq vs 0.9% non-sq), and PIK3CA mut + PTEN mut + PTEN neg (0.2% sq vs 0% non-sq). No clear gender, age or ethnicity effects were observed (Table). Figure 1
The findings from our large dataset indicate that genetic alterations in the PI3K pathway occur in a clinically significant proportion of pts with sq and non-sq relapsed NSCLC. An accurate characterization of PI3K pathway alteration frequencies in NSCLC will help guide the design of future clinical trials of PI3K inhibitors.
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