Is O-FC as good as FCR?

The MDACC lot have published the results of a phase 2 trial of FC with Ofatumumab in 61 previously untreated CLL patients. The question we all want to know is whether O-FC is likely to be an improvement on FCR.

The problem with a phase 2 study is that there is no comparison that is valid. All you can do is look at other phase 2 studies and make a rough judgement.

So what is the competition like? The CALGB 9712 trial reported at CR rate of 47% and an OR rate of 90% for FR. The MDACC FCR response rate was 72% CR and 95% OR. The Spanish FCM-R rates were 82% CR and 93% OR. But the German CLL8 study reported a more realistic 44% CR rate and 95% OR, All these studies were in relatively young and fit patients.

However, the O-FC study was a bit more stringent in some respects, though not all. The patients were still young with a median age of 56, but they included 13% with a del 17p and 16% with del 11q. 64% had a Beta-2M level greater than 3.5. 47% were unmutated and 20% had a raised CD38. Of particular note was the OR of 63% and CR rate of 13% in del 17p patients.

The overall incidence of toxicity and failure to complete treatment was similar to the MDACC experience with FCR.

The FC was given in standard doses but the O was given as either 500 or 1000 mg (not per sq m). The OR rate was 77% and 73% for the two doses respectively (ie not statistically different) but the CR rate was 50% for the higher dose and 32% for the lower (not statistically different, though because of small numbers). By univariate analysis the factors determining response were completion of sufficient courses of treatment and the Beta-2M level.

What can we say then, is O-FC as good as FCR? This small study is unable to say more than it might be. We shall have to await head to head comparisons.