Abstract 3393
Background
Mutations in PIK3CA, an EGFR downstream effector, and the subsequent activation of AKT pathway plays an important role in colorectal carcinogenesis. Considering the frequent co-occurrence of PIK3CA and RAS mutations, conflicting data exist about its impact on prognosis of mCRC patients (pts) and its predictive role to anti-EGFR therapy. However, PI3K inhibitors have been developed and are currently under investigation in mCRC.
Methods
Data from mCRC pts treated at Azienda Ospedaliero-Universitaria Pisana from 1 Jan 2005 to 31 Dec 2017, whose tumours had been analysed per clinical practice by MALDI-TOF MassArray were retrieved. Association between PIK3CA mutation and clinico-pathological features was analysed by χ2 test; OS curves were estimated with Kaplan-Meier method and compared by log-rank test.
Results
Tumours from 90 (17%) out of 542 pts included in this analysis were PIK3CA mutated (mut), most of them in exon 9 (58.9%) or 20 (21.1%). Compared to PIK3CA wild-type (wt) tumours, mut ones were more often RAS mut (P = 0.006), MSI high (P = 0.008), and right-sided (P = 0.0004). Among 53 pts for whom PIK3CA status was available on both primary tumours (PT) and metastasis, the concordance was 92.4%. PIK3CA mutations were not associated with OS (36.4 vs 35.9 mos, HR 1.17, 95%CI 0.85-1.62, p = 0.3), with no difference among those affecting exon 9 and 20 (36.4 vs 27.5 mos, HR 0.77, 95%CI 0.39-1.54, p = 0.44). In RAS/BRAF wt (N 188) and in RAS mut (N 299) subgroup, no difference in terms of OS was found between PIK3CA mut and wt pts (38.1 vs 44.4 mos, HR 1.22, 95%CI 0.60-2.48, p = 0.55 and 27.5 vs 34.4 mos, HR 1.26, 95%CI 0.85-1.86, p = 0.22, respectively), though PIK3CA mut had shorter OS. In BRAF mut subgroup (N 54), PIK3CA mut pts had longer OS compared to PIK3CA wt (not reached vs 14.4 mos, HR 0.37, 95%CI 0.16-0.85, p = 0.09). Among 39 chemorefractory RAS/BRAF wt pts evaluable for response to an anti-EGFR agent, only 2 were exon 9 PIK3CA mut and achieved stable disease.
Conclusions
PIK3CA mut tumours displayed specific clinico-pathological features and a strong concordance was found between PT and paired metastases. Interestingly, a different impact on prognosis of PIK3CA mutation in RAS/BRAF wt, RAS mut or BRAF mut mCRC pts was observed and deserves validation.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Supported by ARCO (Associazione Ricerca e Cure in Oncologia) Foundation.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
5773 - A prospective study of diffusion-weighted magnetic resonance imaging for predicting outcome following chemoradiotherapy, in squamous cell carcinomas of the anus.
Presenter: Rebecca Muirhead
Session: Poster Display session 2
Resources:
Abstract
4581 - Timing to achieve complete response (CR) after definitive chemoradiotherapy (ChRT) in patients with squamous cell carcinoma of the anal (SCCAC) with and without HIV infection: a multicenter retrospective study
Presenter: Marcos Camandaroba
Session: Poster Display session 2
Resources:
Abstract
1712 - Planned organ preservation for T2 T3 M0 rectal adenocarcinoma. A possible option using chemoradiotherapy (CRT) and Contact X-ray Brachytherapy (CXB). A French multicenter study.
Presenter: Jean-Pierre Gérard
Session: Poster Display session 2
Resources:
Abstract
4639 - A Phase 1b Study of E7046 (AN0025) in Combination With Radiotherapy/Chemoradiotherapy (RT/CRT) in Preoperative Treatment of Rectal Cancer
Presenter: Lucjan Wyrwicz
Session: Poster Display session 2
Resources:
Abstract
2310 - Upfront radical surgery with total mesorectal excision (TME) versus preoperative chemoradiotherapy followed by TME in clinical stage II/III patients with rectal cancer: a propensity score analysis
Presenter: Ahrong Ham
Session: Poster Display session 2
Resources:
Abstract
2747 - Neoadjuvant chemoradiotherapy with/without lateral lymph node dissection for low rectal cancer: Which patients can benefit?
Presenter: Daisuke Nishizaki
Session: Poster Display session 2
Resources:
Abstract
2877 - The impact of completeness of chemotherapy on the efficacy of irinotecan in the preoperative chemoradiotherapy of locally advanced rectal cancer.
Presenter: Jingwen Wang
Session: Poster Display session 2
Resources:
Abstract
3050 - Feasibility of robot-assisted surgery in elderly patients with rectal cancer
Presenter: Wei-Chih Su
Session: Poster Display session 2
Resources:
Abstract
4109 - Feasibility of chemoradiotherapy in rectal cancer patients with peritumoral abscesses and fistulas: a case-control non-inferiority trial
Presenter: Valerii Ivanov
Session: Poster Display session 2
Resources:
Abstract
4813 - Differential of the nutritional index before and after neoadjuvant chemoradiotherapy as a prognostic factor of recurrence in patients with locally advanced adenocarcinoma of the rectum
Presenter: Leslie Navia-Ortuño
Session: Poster Display session 2
Resources:
Abstract