The pathway alteration load is a pan-cancer determinant of outcome of targeted therapies: results from the Drug Rediscovery Protocol (DRUP).

Background: Many patients with cancer exhibit primary or rapid secondary resistance to targeted therapy (TT). We hypothesized that a higher number of altered oncogenic signaling pathways [pathway alteration load (PAL)] would reduce the benefit of TT which only intervenes in one pathway. This hypothesis was tested in the Drug Rediscovery Protocol (DRUP).

Patients and methods: DRUP is a prospective, pan-cancer, non-randomized clinical trial (NCT02925234) that treats patients with therapy-refractory metastatic cancer and an actionable molecular profile using matched off-label targeted and immunotherapies. All patients treated with TT with available clinical outcomes and whole genome sequencing were included. PAL was determined based on driver gene alterations and correlated with clinical benefit rate (CBR), progression-free survival (PFS) and overall survival (OS). Outcomes were validated in the independent Hartwig Medical database of metastatic cancers.

Results: In 154 patients treated with TT, the median PAL was 3. Patients with a PAL below median (n = 60) demonstrated a higher CBR (41.7% versus 25.5%, odds ratio 0.48, P = 0.051), longer PFS [median 4.7 versus 2.9 months, adjusted hazard ratio (aHR) 1.70, P = 0.020] and OS (median 13.7 versus 5.6 months, aHR 3.80, P < 0.001) compared with those with PAL ≥3. Two hundred and fifty-eight patients in the Hartwig database showed similar results for CBR (54.2% versus 36.7%, odds ratio 2.04, P = 0.009) and PFS (7.0 versus 4.2 months, aHR 1.55, P = 0.009).

Conclusions: In our population, PAL emerged as a pan-cancer determinant of outcome to TT. Our findings support refined patient selection for TT and highlight the rationale for combinatorial treatment strategies in patients with multiple affected pathways.