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P1.01 - Poster Session/ Treatment of Advanced Diseases – NSCLC (ID 206)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 1
- Coordinates: 9/07/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
P1.01-001 - Pembrolizumab for Advanced NSCLC: Patterns of Response and Progression (ID 1005)
09:30 - 17:00 | Author(s): J.H. Lee
Anti-PD1 therapy has activity in patients with NSCLC, as assessed by RECIST or immune-related response criteria (irRC) on selected index lesions. Baseline tumour size was reported as an independent predictor of response to pembrolizumab in melanoma, but little is known about NSCLC. Tumour burden varies depending on number and size of lesions. We investigate the relationship of treatment response and baseline disease burden using comprehensive lesion-specific analysis on imaging at a single centre from a large multicentre Phase I study.
Clinicopathologic characteristics of patients with advanced NSCLC enrolled from May 2012 to April 2014 at Westmead Hospital on the phase I pembrolizumab (MK-3475) KEYNOTE-001 were collected, including age, ethnicity, smoking status, histopathology (squamous or non-squamous), stage and prior treatments. Patients were treated with pembrolizumab until disease progression determined by irRC on index lesions or intolerable toxicity. Bi-dimensional measurements of individual lesions on computed tomography scans at baseline, week 9 and thereafter were performed. Every metastasis ≥5mm (up to 30 lesions per organ, excluding bone) and every lymph node ≥15mm in the short axis were assessed. Overall response was determined by change in sum of the product of longest perpendicular diameters (SPD) and categorised as complete response (CR, 100% reduction SPD), partial response (PR, ≥50% reduction SPD), progressive disease (PD, ≥25% increase in SPD) or stable disease (SD, neither CR/PR/PD) using comprehensive lesion-specific analysis.
Of 25 evaluable patients with at least one post-baseline imaging, 12 were treatment-naïve, 21 were PD-L1 positive (>1% staining of cells) determined by prototype assay using 22C3 antibody and 4 were unknown. A total of 226 lesions were evaluated, 196 at baseline and 22 new lesions by first scan. Objective response (OR, ≥50% reduction SPD) was achieved in 9/25 patients (36%) by first scan, with 1 out of the 9 patients subsequently achieving CR. The patients with treatment response by first scan had a lower median number of lesions at baseline, 4.0 (range 2-8) vs 8.5 (range 4-30) and a lower median SPD per patient at baseline, 2516 vs 4178.5 Clinical benefit (CR/PR/SD) occurred in 15/25 patients (60%) with median treatment duration of 18.4 months (range 2.8 – 33.5 months). At the time of analysis on 11 April 2015, 10/25 patients were still receiving ongoing treatment. Clinical benefit was seen in 14/17 Caucasians and 1/8 non-Caucasians; 14/16 current or former smokers and 1/9 non-smokers. However, all Asians but one were non-smokers and this ex-smoker was the only Asian patient who achieved SD as best response. No differences were found in histopathology, stage, number of prior treatments or age.
Fewer lesions or lower tumour burden at baseline as determined by comprehensive lesion-specific analysis may predict treatment response to anti-PD1 in advanced NSCLC. More responses were also observed in Caucasians and current or former smokers. Due to small sample size, these results need to be interpreted with caution and warrant further investigation.
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