REPORTING FROM THE 2018 GI CANCERS SYMPOSIUM

SAN FRANCISCO (FRONTLINE MEDICAL NEWS) – Two new therapies that target vascular endothelial growth factor signaling are efficacious and may expand the treatment armamentarium for intermediate and advanced hepatocellular carcinoma, data from a pair of randomized trials suggest.

In the phase 2 TACTICS (Transcatheter Arterial Chemoembolization Therapy in Combination With Sorafenib) trial, median progression-free survival, using a new, more narrow definition of progression, was almost a year longer when the oral tyrosine kinase inhibitor sorafenib (Nexavar) was added to transarterial chemoembolization (TACE) for unresectable hepatocellular carcinoma (HCC), translating to a 41% reduction in risk of events. This benefit came at the price of higher rates of certain grade 3 adverse events, but the combination was overall feasible and safe.

In the phase 3 CELESTIAL trial , median overall survival was about 2 months longer with the oral tyrosine kinase inhibitor cabozantinib(Cabometyx, Cometriq) than with placebo among patients with advanced HCC who had previously received sorafenib, translating to a 24% reduction in risk of death. The rate of grade 3 or 4 adverse events was about twice as high with cabozantinib, but treatment discontinuation because of events was uncommon.

Results of both trials were reported at the 2018 GI Cancers Symposium, sponsored by the American Gastroenterological Association, the American Society for Clinical Oncology, the American Society for Radiation Oncology, and the Society of Surgical Oncology.

As welcome as such new therapeutic options are, they will likely increase the complexity of the treatment landscape for HCC and could muddy the ability of future trials to establish survival benefit, Jordi Bruix, MD, PhD , cautioned in an invited discussion. In addition, patients who cannot receive anti–vascular endothelial growth factor (VEGF) therapy because of comorbidities still represent an unmet need, underscoring the importance of continued research on other fronts.

TACTICS trial

“Because TACE has been shown to lead to a spike in the intratumoral concentration of VEGF, blockade of VEGF receptors may prevent the effects of a surge in proangiogenic factors,” said TACTICS lead investigator Masatoshi Kudo, MD, professor and chairman of the department of gastroenterology and hepatology at Kindai University, Osaka, Japan. “Since TACE and sorafenib have been shown to prolong survival in patients with unresectable HCC, their combination may improve clinical outcomes.”

The 156 patients enrolled in the TACTICS trial, sponsored by the Japan Liver Oncology Group, had unresectable HCC, a Child-Pugh score of 7 or lower, and no vascular invasion or extrahepatic spread.

They were randomly assigned to as-needed TACE alone or TACE plus sorafenib, which inhibits VEGF receptors, platelet-derived growth factor receptors, and Raf kinases, reducing growth signaling and angiogenesis. Sorafenib therapy was interrupted only for several days before and after each TACE session.

In the trial, new intrahepatic lesions were not considered to be progression signaling treatment failure, but rather the natural biology of HCC, Dr. Kudo explained.

With a median follow-up of 2.4 years, median progression-free survival using a new definition of progression – either untreatable “unTACEable” disease or TACE failure/refractoriness (by Japanese Society of Hepatology criteria) – was 25.2 months with TACE plus sorafenib compared with 13.5 months with TACE alone (hazard ratio, 0.59; P = .006). Benefit was similar across patient subgroups.

Overall survival results are not yet mature, according to Dr. Kudo. Overall response rate and disease control rate did not differ significantly between groups.

Adding sorafenib to TACE led to higher rates of certain grade 3 adverse events, including thrombocytopenia (12.8% vs. 2.8%), hand-foot skin reaction (5.1% vs. 0%), and hypertension (10.3% vs. 4.2%). But there were no unexpected events.

The trial’s positive results contrast with those of the earlier randomized Post-TACE trial, SPACE trial, and TACE 2 trial, noted Dr. Kudo. This may be due to both the new, narrower definition of progression and the longer duration of sorafenib therapy in TACTICS (median 38.7 weeks) as compared with those trials (17.0-21.0 weeks).

“The TACTICS trial clearly showed TACE in combination with sorafenib is a treatment option to improve clinical outcome and may be a standard of care in patients with intermediate-stage HCC,” he concluded.

CELESTIAL trial

The 707 patients in the phase 3 CELESTIAL trial, sponsored by Exelixis, had advanced HCC with Child-Pugh class A and had previously received sorafenib. About 70% had received only one prior systemic regimen for their advanced disease, according to lead investigator Ghassan K. Abou-Alfa, MD , a medical oncologist at the Memorial Sloan Kettering Cancer Center, New York.

They were randomized 2:1 to cabozantinib or placebo. Cabozantinib inhibits VEGF receptors, as well as MET and AXL, which are associated with resistance to VEGF receptor–targeted therapy.

Median overall survival was 10.2 months with cabozantinib and 8.0 months with placebo (HR, 0.76; P = .0049). Median progression-free survival was 5.2 months and 1.9 months, respectively (HR, 0.44; P less than .0001). For both outcomes, benefit was similar across most patient subgroups and among patients whose only prior therapy was sorafenib.

The objective response rate was 4% with cabozantinib (all partial responses) and 0.4% with placebo. Median time to subsequent systemic anticancer therapy – most commonly cytotoxic chemotherapy – was 6.6 months with the drug and 3.3 months with placebo.

Median duration of treatment was 3.8 months and 2.0 months, respectively. The rate of discontinuation from treatment-related adverse events was 16% and 3%.

Grade 3 or 4 adverse events occurred in 68% of patients in the cabozantinib group (mainly hand-foot syndrome, hypertension, and gastrointestinal events) and 36% in the placebo group. Six patients in the former group and one in the latter group had grade 5 treatment-related adverse events, most due to worsening of hepatic function.

“Cabozantinib represents a new treatment option for advanced HCC patients after prior systemic anticancer therapy,” concluded Dr. Abou-Alfa.

New treatments increase options, complexity

The new endpoint of unTACEable progression used in TACTICS “is an interesting potential surrogate endpoint for survival. It probably needs to be refined. I would not follow exactly the Japanese methodology,” said Dr. Bruix, the invited discussant.

“More importantly, it needs to be validated,” he added. “The survival data need to be there to see what is the value of the surrogate intermediate endpoint.”

The pattern of overall survival thus far suggests that an early advantage from adding sorafenib to TACE is lost over time. “Potentially, what we have here is the treatment maintained a bit beyond what would be recommended in the Western guidelines,” proposed Dr. Bruix, professor of medicine at the University of Barcelona and director of the Barcelona Clinic Liver Cancer Group. “The longer duration of sorafenib obviously may be related to the specific management in Japan, but also to the fact that progression recognition is delayed. If you delay recognition, you delay the definition of treatment interruption.”

Results of TACTICS probably will not lead to incorporation of sorafenib in clinical practice at this time, he concluded. “This will take a while. There is lots of noise in the chemoembolization trials, there are lots of discussions about what should be done.” In addition, “this should be studied in the West and in a large sample size.”

In the CELESTIAL trial, it would have been helpful to see biomarker data (given that tumor MET status may influence benefit from cabozantinib) and patient stratification according to reason for stopping prior sorafenib (intolerance versus progression), according to Dr. Bruix.

Furthermore, pattern of progression was not reported. “What drives a poorer outcome [in HCC] is the extrahepatic dissemination, meaning vascular invasion or extrahepatic spread. The trials, at least as a post hoc analysis, should have nowadays this kind of analysis that I think is not going to be available in the cabozantinib trial,” he said.

The fact that time to progression with cabozantinib was longer than time on the drug hints at possible safety and tolerability issues, according to Dr. Bruix. “This makes me suspect that some patients had something prior to progression that primed treatment interruption. This is something that I would like to see better explored … to understand to what extent the drug is safe, can be managed, or whether there are too many treatment interruptions that can lead to this discrepancy.”

All of the emerging systemic therapies for first- and second-line therapy in HCC, now also including immune checkpoint inhibitors, are likely to complicate the treatment landscape in the next few years, he cautioned. “The positioning of agents and the sequencing of treatments is different across the world. So there may be confusion in the field and that will affect all the trials that are going to be run by different companies, because if we do not maintain the discipline, patients will jump from one trial to the other and the follow-up after progression will be contaminated.” Ultimately, this could lead to noninformative trials.

Finally, “something that needs to be stated is that all the agents that are positive act on the VEGF pathway. This leaves a proportion of patients that cannot benefit from these agents because of comorbidity that are still in need of something that improves survival,” Dr. Bruix concluded. “We all should focus beyond VEGF and try to develop new strategies.”

op@frontlinemedcom.com

SOURCE: Kudo M et al. GI Cancers Symposium, Abstract 206. Abou-Alfa GK et al. GI Cancers Symposium, Abstract 207.

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