Spontaneous Remission of Chronic Lymphocytic Leukemia, Possibly More Rare Then Previously Reported?

Spontaneous remission of chronic lymphocytic leukemia (SRCLL) has occassionaly been reported since the 1950s. About 40–50 cases have been reported in the English literature. The often quoted incidence of such a phenomena is estimated to be 1% of all CLL cases (Table 1). However, a review of these reports which have determined this incidence suggests that many patients did not have a true SRCLL. The authors have conducted a systemic search within their own institution database to determine the true incidence of SRCLL.

After obtaining appropriate IRB approval, a systemic search was performed within the our institution's hematopathology databases for the diagnosis of chronic lymphocytic leukemia from year 2000 to 2012. Records and laboratory findings were reviewed for all cases. Records for patients with laboratory data suggestive of remission were reviewed to determine if they had received any form of therapy. All cases were included in the review if the diagnosis of CLL was firmly established by flow cytometry. SRCLL was defined as: 1) the patient's elevated lymphocyte number at diagnosis was >5 × 10⁹/L and persisted for >6 months confirming the initial diagnosis of CLL, 2) the lymphocyte number subsequently normalized to <5 × 10⁹/L, the lymphocyte count remained normal for greater than 9 months, 3) resolution of other features of CLL such as lymphadenopathy, and 4) no intervening treatment was given to patients, including radiation therapy or steroids.

After reviewing 167 cases, only one case met our inclusion criteria, with an estimated incidence of 0.6%.

Spontaneous remission of CLL is a rare phenomenon. This review suggests that the incidence of SRCLL is less then the previously often quoted incidence of 1% and may more appropriately approximate 0.6%.

No relevant conflicts of interest to declare.