Response rates: a valuable signal of promising activity?

[Biosimilars antibodies: positioning compared to originators - the experience in rheumatology and the biosimilars of trastuzumab in oncology]

Biosimilars have demonstrated their equivalence with biologic originators, according to rigorous specifications imposed by the regulatory agencies, the FDA and the EMA. Their development is justified by the very high cost of biopharmaceuticals, and strong incentives for their prescription lead us to hope substantial savings, allowing to finance other innovative molecules. Trastuzumab marked history of the treatment of breast cancer. Four biosimilars of trastuzumab are available for routine use and we will detail the key points of their development.

Can we establish a hierarchy among trastuzumab biosimilar candidates?

The European patent for intravenous trastuzumab lapsed in 2017, and this stimulated research into a number of trastuzumab biosimilars. Quality assessment of their development and clinical results might enable establishment of a clinical hierarchy of these agents. This editorial will underline the key points for consideration when determining such an evaluation.

Evaluation of alternate categorical tumor metrics and cut points for response categorization using the RECIST 1.1 data warehouse

PURPOSE

We sought to test and validate the predictive utility of trichotomous tumor response (TriTR; complete response [CR] or partial response [PR] v stable disease [SD] v progressive disease [PD]), disease control rate (DCR; CR/PR/SD v PD), and dichotomous tumor response (DiTR; CR/PR v others) metrics using alternate cut points for PR and PD. The data warehouse assembled to guide the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 was used.

METHODS

Data from 13 trials (5,480 patients with metastatic breast cancer, non-small-cell lung cancer, or colorectal cancer) were randomly split (60:40) into training and validation data sets. In all, 27 pairs of cut points for PR and PD were considered: PR (10% to 50% decrease by 5% increments) and PD (10% to 20% increase by 5% increments), for which 30% and 20% correspond to the RECIST categorization. Cox proportional hazards models with landmark analyses at 12 and 24 weeks stratified by study and number of lesions (fewer than three v three or more) and adjusted for average baseline tumor size were used to assess the impact of each metric on overall survival (OS). Model discrimination was assessed by using the concordance index (c-index).

RESULTS

Standard RECIST cut points demonstrated predictive ability similar to the alternate PR and PD cut points. Regardless of tumor type, the TriTR, DiTR, and DCR metrics had similar predictive performance. The 24-week metrics (albeit with higher c-index point estimate) were not meaningfully better than the 12-week metrics. None of the metrics did particularly well for breast cancer.

CONCLUSION

Alternative cut points to RECIST standards provided no meaningful improvement in OS prediction. Metrics assessed at 12 weeks have good predictive performance.

Comparison of continuous versus categorical tumor measurement-based metrics to predict overall survival in cancer treatment trials

PURPOSE

The categorical definition of response assessed via the Response Evaluation Criteria in Solid Tumors has documented limitations. We sought to identify alternative metrics for tumor response that improve prediction of overall survival.

EXPERIMENTAL DESIGN

Individual patient data from three North Central Cancer Treatment Group trials (N0026, n = 117; N9741, n = 1,109; and N9841, n = 332) were used. Continuous metrics of tumor size based on longitudinal tumor measurements were considered in addition to a trichotomized response [TriTR: response (complete or partial) vs. stable disease vs. progression). Cox proportional hazards models, adjusted for treatment arm and baseline tumor burden, were used to assess the impact of the metrics on subsequent overall survival, using a landmark analysis approach at 12, 16, and 24 weeks postbaseline. Model discrimination was evaluated by the concordance (c) index.

RESULTS

The overall best response rates for the three trials were 26%, 45%, and 25%, respectively. Although nearly all metrics were statistically significantly associated with overall survival at the different landmark time points, the concordance indices (c-index) for the traditional response metrics ranged from 0.59 to 0.65; for the continuous metrics from 0.60 to 0.66; and for the TriTR metrics from 0.64 to 0.69. The c-indices for TriTR at 12 weeks were comparable with those at 16 and 24 weeks.

CONCLUSIONS

Continuous tumor measurement-based metrics provided no predictive improvement over traditional response-based metrics or TriTR; TriTR had better predictive ability than best TriTR or confirmed response. If confirmed, TriTR represents a promising endpoint for future phase II trials.

Phase II trial of paclitaxel and uracil--tegafur in metastatic breast cancer. TEGATAX trial

This Phase II trial investigated the combination paclitaxel (P) and uracil-tegafur (UFT) in patients with metastatic breast cancer (MBC).

METHODS

Main eligibility criteria included HER-2 negative MBC, ECOG performance status of 0-2, exposure to 1-2 prior chemotherapy regimen in the metastatic setting, previous exposure to an anthracycline containing regimen either at metastatic or adjuvant setting. Each 35-day cycle consisted of P at 80 mg/m(2) by intravenous infusion on days 1, 8, 15, 22 and 29 and oral UFT at 300 mg/m(2) TID (three time a day) from days 1-28 and oral folinic acid at 90 mg QD (one a day).

RESULTS

Between March 2003 and December 2007, 31 patients were enrolled. Median age was 66 years (range 44-78). All tumours were HER-2 negative and 7% were triple negative (ER, PgR, HER-2). The majority of patients had visceral disease (81%). All patients had received an anthracycline containing regimen and 74% had a previous docetaxel containing treatment. Median of 4 and 3 cycles of P and UFT were administered with a relative dose intensity of 85.3% and 94.3%, respectively. Twelve (40%)(95% CI: 22.5-57.5) confirmed ORR were observed. Stable and progression disease were reported in 43% and 17% of cases. Median Response duration was 8.4 month (95% CI: 4.9-11.7), median Time to progression was 9.5 months (95% CI: 6.6-13.8) and median Overall Survival was 23.5 months (95% CI: 16.8-37.2). Thirteen pts (43%) experienced a grade 3 or 4 adverse events (AEs): One death occurred related to the study drugs (febrile neutropenia). Chemotherapy was discontinued due to toxicity in 30% of pts

CONCLUSIONS

Accrual was closed in January 2008 due to concerns regarding the degree and accumulative nature of AEs. Nonetheless, the ORR is encouraging and warranted further studies with adapted doses and schedules.

A multicentre dose-escalating study of cabazitaxel (XRP6258) in combination with capecitabine in patients with metastatic breast cancer progressing after anthracycline and taxane treatment: a phase I/II study

BACKGROUND

Most patients with metastatic breast cancer (MBC) progress after chemotherapy. Cabazitaxel (XRP6258) is a new taxoid that is active in chemotherapy-resistant tumour cell lines. The objectives of this phase I/II study were to assess the maximum tolerated dose (MTD), safety profile, pharmacokinetics, and activity of cabazitaxel plus capecitabine in patients with MBC who had been previously treated with taxanes and anthracyclines.

PATIENTS AND METHODS

In part I, we used a 3+3 dose-escalation scheme to assess the MTD of intravenous cabazitaxel (day 1) with oral capecitabine twice daily (days 1-14) every 3 weeks. In part II, we evaluated the objective response rate (ORR) at the MTD.

RESULTS

Thirty-three patients were enrolled and treated (15 in part I; 18 in part II). Cabazitaxel 20mg/m(2) plus capecitabine 1000 mg/m(2) was the MTD. Pharmacokinetic analysis showed no apparent drug-drug interaction. In all patients, the main grade 3-4 toxicities were asthenia (n=5), hand-foot syndrome (n=5), neutropenia (n=21), neutropenic infection (n=1), and neutropenic colitis (n=1). One patient had febrile neutropenia. Antitumour activity was observed at all dose-levels with two complete responses, five partial responses (PRs), and 20 disease stabilisations (seven unconfirmed PR). At the MTD, 21 patients were evaluable for efficacy. The ORR was 23.8% (95% CI: 8.2-47.2%). The median response duration was 3.1 months (95% CI: 2.1-8.4 months), with four of five lasting for more than 3 months. Median time to progression was 4.9 months.

CONCLUSIONS

Cabazitaxel combined with capecitabine is active, has a safety profile consistent with a taxane plus capecitabine combination and warrants further investigation in patients with MBC.