Ca-15.3 antigen as predictor of response to EGFR inhibitors in patients with bronchiolo-alveolar carcinoma

18151 Background: Bronchiolo-alveolar carcinoma (BAC) is a subtype of non-small cell lung cancer (NSCLC). Incidence of pure BAC ranges between 2% and 5% of NSCLC although a BAC histotype may be present in up to 20%. There is no established treatment for BAC, although promising results have been achieved from the use of inhibitors of the Epidermal Growth Factor Receptor (EGFR). It has been demonstrated that there is a very close relationship between responsiveness to EGFR inhibitors Erlotinib and Gefitinib and some factors, including female gender; adenocarcinoma histotype, with BAC features; Asian origin; and never having smoked. No tumor marker has been validated in the diagnosis and follow-up of lung cancer. Ca 15–3 antigen serum levels are reported to be pathologically abnormal in adenocarcinoma of the lung, although it does not seem to be related to the EGFR pathway. We studied this tumor marker in relation with the treatment with EGFR inhibitors in patients affected by BAC. Methods: We collected data from 16 caucasian, female and never smoker pts with BAC. All pts received EGFR inhibitors as first-line therapy. In compliance with the EAP, dosage of Gefitinib and Erlotinib was 250 mg/day and 150 mg/day, respectively. Results: One (6%) pt had a complete response and 6 (38%) showed a partial response to EGFR inhibitors, 1 (6%) pt remained stable for 4 months, while 8 (50%) pts progressed. All 7 pts with normal Ca 15–3 levels before treatment with EGFR inhibitors’ achieved a partial or complete response, but the 8 pts with abnormal Ca 15–3 levels did not (p=0.0001). Among the responders we noticed an increase of Ca 15–3 serum levels at progression. In particular, 5 pts had an increase of Ca 15–3 serum levels up to normal value when their disease progressed; 2 pts have not progressed yet and Ca 15–3 serum levels remain normal. Conclusions: We suggest that Ca 15–3 levels may be a prognostic factor to predict the response to EGFR inhibitors in pts with BAC. We are studying its role in a larger population with BAC and in other NSCLC subtypes as well. No significant financial relationships to disclose.