Utilizing Clinical Features of Progression to Predict Richter's Syndrome in Patients with CLL Progressing after Ibrutinib

Background:

Aggressive lymphoma arising in the setting of chronic lymphocytic leukemia (CLL), known as Richter's syndrome (RS), is associated with poor outcomes with standard of care therapies. There is limited capacity for PET-CT to distinguish patients (pts) who develop RS after ibrutinib (Mato Haematologica 2019). Data on outcomes of pts with RS having previously received ibrutinib is limited. Here we sought to determine if clinical characteristics associated with iwCLL criteria for progression (Hallek Blood 2018) predict the risk of RS and overall survival (OS) in pts treated with ibrutinib.

Methods:

We conducted a retrospective analysis of pts with CLL treated with ibrutinib from 2010-2019 at The Ohio State University. We identified pts that progressed after ibrutinib and classified the progression by 2018 iwCLL criteria. We then identified who developed RS on or after progression. Risk of developing RS was assessed through Fine and Gray model treating death as the competing risk. OS was measured from time of progression and estimated using Cox model.

Results:

We analyzed 559 pts who had received ibrutinib for CLL, and identified 179 pts who progressed per iwCLL criteria. 94% of the pts who progressed were relapsed/refractory prior to ibrutinib. 116 pts progressed on ibrutinib, and the median time to progression from ibrutinib start was 40.8 months (mos) (range: 0.2-103.9). 63 pts progressed after stopping ibrutinib due to an adverse event or development of a resistance mutation, and the median time to progression from ibrutinib start for these pts was 28.5 mos (range: 0.7-92.9).

Of the 179 pts who progressed, 54 developed RS. Of these 54 pts; 83% had enlarging lymphadenopathy, 9% had an enlarging liver or spleen, 17% had constitutional symptoms, 31% had increasing lymphocytosis, 15%, 15%, and 2% had worsening thrombocytopenia, anemia, or neutropenia respectively. No pts had worsening of CLL in the bone marrow (BM) and 2% had new appearance of other organ involvement. As lymphadenopathy and lymphocytosis were the most common clinical features identified we analyzed them jointly; 61% had lymphadenopathy without lymphocytosis, 9% had lymphocytosis without lymphadenopathy, 22% had both, and 7% had neither.

Among pts with RS, median time from progression to RS was 0.4 mos (range: 0-49.3). Nine pts had biopsy confirmed RS on the date of progression. Median time from ibrutinib start to RS was 27.8 mos (range: 0.7-92.9). We performed a univariable analysis to determine whether clinical signs of relapse were associated with subsequent risk of RS, and found that presence of lymphadenopathy without lymphocytosis at progression was significantly associated with risk of RS (HR 3.58, 95% CI 1.44-8.88, p=0.006) (Table 1, Figure 1A).

To determine if there was an association between clinical features of progression and OS we evaluated all 179 pts that progressed; 72% had enlarging lymphadenopathy, 10% had an enlarging liver or spleen, 15% had constitutional symptoms, 46% had increasing lymphocytosis, 15%, 17%, and 2% had worsening thrombocytopenia, anemia, or neutropenia respectively, only 2% had worsening of CLL in the BM, and 1% had new appearance of other organ involvement. When analyzed jointly; 45% had lymphadenopathy without lymphocytosis, 20% had lymphocytosis without lymphadenopathy, 26% had both, and 9% had neither.

Median OS from progression was 24.4 mos (95% CI: 18.6-45.5), while median OS from RS diagnosis was 4.0 mos (95% CI: 2.1-7.1). Median OS from progression was 15.2 mos (95% CI: 7.8-24.6), and 49.9 mos (95% CI: 20.0-NR) for the lymphadenopathy without lymphocytosis and the lymphocytosis without lymphadenopathy groups respectively (Figure 1B). On univariable analysis lymphadenopathy without lymphocytosis was associated with a shorter OS (Table 1). These findings were maintained on multivariable analysis, with lymphadenopathy without lymphocytosis remaining an independent predictor of OS (HR 2.12, CI 1.17-3.87, p=0.01).

Conclusions:

Here we show that pts who have received prior ibrutinib for CLL who progress with lymphadenopathy have a higher likelihood of having RS than those pts who progress without lymphadenopathy. Furthermore, pts who progressed with lymphadenopathy without lymphocytosis have a shorter OS. Our data suggests that consideration should be given to perform a biopsy to rule out RS in any pts progressing with lymphadenopathy after receiving ibrutinib therapy for CLL.

Figure 1

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Figure 1

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