EGFR mutations (seen in 15 of 89 patients) were also statistically significantly related to response and time to progression, but the association with survival was not statistically significant, and 40% of the patients with mutation had progressive disease.
Tumours from 31 patients with metastatic colorectal cancer who had either an objective response (n=10) or stable disease or progressive disease (n=21) after treatment with cetuximab or panitumumab were screened for genetic changes in EGFR or its immediate intracellular effectors.
The EGFR mutations were seen significantly more frequently in patients with a partial response than in patients with stable disease or progressive disease (P = 0.046, Fisher's exact test).
EGFR mutation was observed in 10 of 27 and significantly more frequently observed in the posttreatment samples from patients with a partial response or stable disease than in those from patients with progressive disease (p = 0.006).
We compared amphiregulin expression using immunohistochemistry in EGFR wild-type NSCLC patients (n=24) that developed either stable or progressive disease following erlotinib or gefitinib treatment.
Patients with disease control (CR + PR + SD) had tumors with higher EGFR and lower STAT3 expression at baseline compared with patients who had progressive disease (P = .0312 and P = .095, respectively).
EGFRT790M was identified from plasma DNA in 54% (15 of 28) of patients with prior clinical response to gefitinib/erlotinib, 29% (4 of 14) with prior stable disease, and in 0% (0 of 12) that had primary progressive disease or were untreated with gefitinib/erlotinib.
Awareness of this phenomenon with epidermal growth factor receptor tyrosine kinase inhibitors is important for physicians treating patients with NSCLC, so that it is not misinterpreted as progressive disease resulting in premature cessation of effective therapy.
In EGFR promoter methylated and EGFR promoter unmethylated patients, we observed a partial response in 3 (10%) and 13 (59%) patients, respectively (P=0.03), progressive disease was obtained in 19 (63%) and 2 (9%) patients, respectively, with EGFR promoter methylated and EGFR promoter unmethylated tumours (P=0.0001).
The clinical response to EGFR TKIs was reassessed for all patients as follows: 16 of 73 patients had a partial response (21.9%), 12 patients had stable disease (16.5%), and 45 patients had progressive disease (61.6%).
One of seven patients who experienced partial response had EGFR mutations only in the metastasis, and two of seven patients who experienced progressive disease carried wild-type EGFR only in the metastasis.
Twenty-three patients with lung cancer with progressive disease after EGFR-TKI treatment and 21 patients who had never been treated with EGFR-TKIs were studied.
Patients received the second epidermal growth factor receptor-tyrosine kinase inhibitor after experiencing an adverse event or progressive disease on the first epidermal growth factor receptor-tyrosine kinase inhibitor.
TAM counts were significantly higher in patients with progressive disease than in those without (p < 0.0001), a trend that remained in patients with known EGFR mutation status (n = 59) and those with wild-type EGFR (n = 20).
Direct sequencing revealed wild-type EGFR, whereas PNA clamping revealed mutant EGFR, in one of five patients who exhibited progressive disease in response to EGFR tyrosine kinase inhibitor; the cell block of this patient contained a high proportion of tumor cells.
Our results suggest that the continuous inhibition of epidermal growth factor receptor phosphorylation by erlotinib after progressive disease enhances the antitumor activity of chemotherapy.
Eight patients received an EGFR TKI: three cases with G719X plus another mutation had partial responses (PRs) to erlotinib; of three cases with L858R plus another mutation, two displayed PRs and one (with EGFR-L858R+A871G) progressive disease (PD) to erlotinib; one NSCLC with EGFR-L861Q+E709A and one with delL747_T751+R776S had PRs to EGFR TKIs.
Among 26 patients who had received EGFR-TKIs, the mean EGFR mutation content was higher in patients showing partial response (86.1%) or stable disease (48.7%) compared with patients experiencing progressive disease (6.0%) (P = 0.001).