Abstract 1368: The impact of bevacizumab on combination low-dose afatinib and cetuximab therapy in lung cancer cells harboring activated EGFR mutations

Abstract

Abstract Background. The combination of afatinib and cetuximab induced an unprecedented response in lung tumors harboring EGFR T790M in clinical trials (Cancer Discov. 2014). However, up to 20% of patients discontinued treatment due to adverse events, including skin rashes and diarrhea, and the median progression-free survival of the combination therapy was 4.7 months. There is clearly still room for improvement in the therapy. Bevacizumab, a key drug in lung cancer treatment, is thought to have a wide variety of effects, including anti-vascularization, normalization of tumor vasculature, and improved drug delivery. Thus, we hypothesized that the dosage of afatinib and cetuximab could be reduced by combining with bevacizumab, and that the triple therapy might produce better tumor inhibition with tolerable toxicity. Methods. Two lung cancer cell lines, H1975, with EGFR L858R and T790M, and RPC-9, with EGFR exon 19 deletion and T790M, were injected subcutaneously into nude mice as xenograft models. Mice were divided into four groups 10 days after tumor cell inoculation (vehicle, afatinib, afatinib + cetuximab, afatinib + cetuximab + bevcacizumab). Compared with previous reports (afatinib 25 mg/kg, 5 times/week, cetuximab 1 mg/mouse, every 3 days; J. Clin. Invest. 2009), the low dose of afatinib (10 mg/kg, 5 times/week; i.e., 60% less drug) or cetuximab (0.1 mg/mouse, once/week; i.e., 90% less drug) were administered to the mice for 1 month. Bevacizumab was injected at 2 mg/kg twice/week. Following the therapies, the mice were observed for 1 month without treatment. Results. Surprisingly, the triple therapy induced a pathological complete response (pCR) in H1975 and RPC-9 cell xenograft tumors; in contrast, the tumors treated with single or double therapy were inhibited only partially. Furthermore pCR was maintained during the observation period in the triple therapy group. There was no body weight loss in any group. Frozen tumors were obtained from RPC-9 xenograft models after 1 week treatment with each regimen. Expression levels of pEGFR, pAKT, and pERK were decreased in the triple therapy group. CD31-positive blood vessels and Ki-67-positive cells in tumors with triple therapy were reduced significantly versus the tumors in other groups. Cleaved caspase-3 expression in the tumors with triple therapy was positive in a higher number of tumor cells than in the other groups. Conclusions. We demonstrated that a low-dose of afatinib and cetuximab combined with bevacizumab induced pCR in EGFR T790M mutated cell xenograft tumors with no obvious adverse events. We suggest that the suppression of neovascularization and induction of apoptosis may play important roles in the triple therapy. Note: This abstract was not presented at the meeting. Citation Format: Kenichiro Kudo, Kadoaki Ohashi, Eiki Ichihara, Daisuke Minami, Hisao Kubo, Akiko Sato, Yuka Kato, Hideko Isozaki, Hiroe Kayatani, Tomoki Tamura, Mitsune Tanimoto, Katsuyuki Kiura. The impact of bevacizumab on combination low-dose afatinib and cetuximab therapy in lung cancer cells harboring activated EGFR mutations. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1368. doi:10.1158/1538-7445.AM2015-1368