Orlandi et al report on 137 patients with chronic lymphocytic leukemia and deletion 13q followed between 2001 and 2009, 16 of whom were biallelic. The median percentage of abnormal nuclei was higher in patients with a biallelic pattern (73% vs 49%). We evaluated our patients in light of this letter. Similarly to other pretreatment factors that we examined, we did not see any difference between the 2 groups. The median number of abnormal nuclei in the biallelic group was 32.5% (range, 7%-78.5%) versus 34% (range, 8.5%-89.5%) in the monoallelic group. Orlandi et al also report that the baseline percentage of abnormal nuclei was related to progression. We did report that the median percentage of 13q deletion was higher in both groups for those subsequently requiring treatment, but that it did not reach statistical significance. Because the trend was the same in each of the groups, we reexamined this by combining the data from all patients (biallelic and monoallelic). The median number of abnormal nuclei was 44.5% (range, 8.5%-89.5%) in the 46 patients subsequently progressing. In the 130 patients who had not required treatment, the median number of baseline abnormal nuclei was 31.5% (range, 7%-85%; P = .17). As reported in our paper, in the patients (n = 12) in whom fluorescent in situ hybridization (FISH) was performed at the time of treatment, the median percentage of positive cells had increased from 35% to 79%. We examined the data using the cutpoints described in the large series by Van Dyke et al.1 One hundred forty-seven patients had ≤65.5% abnormal nuclei; 34 patients required treatment. Twelve of 29 patients having >65.5% abnormal nuclei required treatment (P = .041). The median time to treatment in the group with <65.5% abnormal nuclei was not reached versus 25 months (P = .021) in the other group. So although the median percentage of abnormal nuclei did not differ, those with a markedly higher percentage of abnormal nuclei at baseline were more likely to progress to treatment and progressed more quickly.
The decision to treat was made using standard criteria and was irrespective of FISH results. Thus, it is unclear what the benefit of frequent monitoring would be, as this would not change the current approach to therapy.