The basal subtype to predict clinical benefit from neoadjuvant chemotherapy: Final results from a phase II clinical trial of DDMVAC plus bevacizumab.

Abstract

291 Background: Gene expression profiling (GEP) suggests 3 main subtypes of urothelial cancer: basal, which historically has the worst prognosis with high proliferation and HIF-1 expression; p53-like, with decreased proliferation and increased markers of extracellular matrix (ECM); and luminal which has increased proliferation compared to p53-like tumors. We hypothesized that GEP of transurethral resections (TUR) and cystectomy specimens from patients on a neoadjuvant trial would predict benefit from chemotherapy. Methods: Sixty patients enrolled on a neoadjuvant trial of DDMVAC+B. TUR and cystectomy specimens were available for gene expression profiling in 39 and 33 patients, respectively, with matched specimens in 23 patients. The validation set consisted of 49 patients treated with perioperative MVAC on a previously published clinical trial. Results: Chemotherapy was quite active with pT0N0 and ≤ pT1N0 down-staging rates of 38% and 53%, respectively. Basal tumors had improved survival compared to luminal and p53-like (5-year OS 91%, 73% and 36%, p=0.015). A validation cohort of patients treated with perioperative MVAC confirmed this survival benefit (5-year OS basal, luminal, and p53-like 77%, 57%, and 57%, respectively, p =0.027). The use of bevacizumab in basal tumors did not confirm evidence of significant benefit in these small numbers of patients (5-year OS bevacizumab: 91% vs MVAC: 77%, p=0.68) Bone metastases within 2 years associated exclusively with the p53-like subtype (p53-like: 100%, luminal: 0%, basal 0%, p≤0.001). The p53-like subtype was enriched at cystectomy (basal to p53-like in 3/5 (60%), luminal to p53-like in 5/7 (71%), suggesting chemo-resistance in p53-like tumors. Conclusions: In contrast to historical expectations, the basal subtype was predictive of clinical outcomes from neoadjuvant chemotherapy, reflecting the impact of chemotherapy on highly proliferative tumors. Bone metastases were associated with the p53-like subtype which is enriched for ECM. We can no longer think of urothelial cancer as one disease; subtyping should be considered for all tumors, and may have implications on selecting therapy. Clinical trial information: NCT00506155.