Abstract P6-10-01: Evaluation of post-progression survival (PPS) in advanced breast cancer (ABC) according to treatment line: Correlation with PFS and OS in an unselected population

Background: MBC remains an incurable disease with a median survival of 2-3 years despite the use of new drugs. The validation of PPS as surrogate endpoint and its correlation to PFS and OS is matter of debate.

Methods: From 2006-2012 we analyzed retrospectively consecutive 192 pts treated for MBC outside of clinical trials, 103 with at least 3 lines CT, in order to evaluate post-progression survival (PPS) according to treatment line and its relation to PFS and OS. Moreover we evaluated the gain of benefit after CT3 and predictive factors of response to multiple lines of therapy.

Results: Median age at M+ diagnosis was 59 years (30-89), median site of disease was 2 (1-6), 67% visceral, HER-2 + pts 32%, median number of anti-Her-2 treatment was 2 (0-6); median number of treatment was 3 (1-8). Median OS for all pts was 45.6 (95% CI: 36.5-54.7). Median OS for CT > = 3 vs CT < 3 was respectively 52.5 (95% CI: 43.3-61.7) and 32.3 (95% CI: 23.6-41.2) P = 0.007. Multivariate Cox analysis showed that OS is related with ER/Pgr status (positive versus negative p<0.0001) number of lines (>3 vs ≤3) p = 0.001 and number of metastatic sites (>2 vs ≤2) p<0.0001. We evaluated the relation between PFS and OS and between PPS and OS until the 6th line of therapy with a linear regression model.

 Median PFS (95% c.i.)Median PPS (95% c.i.)Median OS from M+ diagnosisCorrelation OS-PPSCorrelation OS-PFS1st line11.0 (9.5-12.5)29.9 (18.2-41.6)Not reachedP<0.0001 OS-PPS1P<0.0001 OS-PFS12nd line7.0 (5.8-8.2)20.9 (11.7-30.0)29.1 (17.5-40.7)P<0.0001 OS-PPS2P<0.0001 OS-PFS23rd line5.6 (4.5-6.7)19.5 (14.9-24.1)41.9 (15.5-68.2)P<0.0001 OS-PPS3P<0.0001 OS-PFS34th line5.7 (4.0-7.4)15.3 (13.4-17.2)50.4 (27.4-73.4)P<0.0001 OS-PPS4P<0.0001 OS-PFS45th line3.9 (3.1-4.7)11.2 (7.8-14.5)65.9 (20.8-112.2)P = 0.004 OS-PPS5P<0.0001 OS-PFS56th line3.3 (2.6-4.0)8.2 (2.2-14.2)56.8 (48.7-64.9)P = 0.36 OS- PPS6P = 0.002 OS-PFS6

Conclusion: These results supported the use of chemotherapy after CT3. PFS and PPS are related to OS until the 6th line of treatment. The utility of PPS as surrogate endpoint of OS is a valid hypothesis that could be evaluated in prospective trials of MBC.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-10-01.