Friday leukemia: myth or reality?

To the editor:

“I let him know his name should be Friday, which was the day I saved his life: I called him so for the memory of the time.”^1p177 We wonder if Robinson Crusoe could have been an oncologist, since not only in classic literature but also in modern medicine, some encounters with misfortune seem to favor a Friday. Undoubtedly, most hematologists are familiar with the subgroup of acute leukemias that first present on a Friday. Diagnostic and therapeutic efforts in caring for these patients are some of the most time- and work-intensive procedures in oncology today, and these patients are felt to present on a Friday afternoon, prompting a flurry of activity at the onset of the upcoming weekend. Clearly, we feel that, especially in hematology, all efforts at optimal processing of fresh material from blood and bone marrow in hospitals and study groups organizing multicenter clinical trials are mandatory regardless of the weekday.

The latest revision of the World Health Organization classification of leukemias, however, did not include this category of acute leukemias.²  Moreover, searching the Medline database for “Friday AND leukemia” does not deliver a single relevant article. Since prevalence, prognosis, and clinical characteristics of this entity remain obscure, we here report on our single center's experience with the acute leukemia that we call “Friday leukemia.”

We retrospectively identified 197 patients with newly developed acute myelogenous leukemia referred to our institution between March 1996 and July 2009.

Figure 1A depicts the distribution of these patients according to the weekday of their first admission. Indeed, statistical analysis substantiates the gut feeling of hematologists around the world, since Friday was significantly overrepresented compared with admissions on other working days in our patient cohort (P = .03, χ² test). Since biochemists hitherto have failed to show weekday-dependent growth kinetics of malignant cells, it can be speculated that factors pertaining to the patients or the health care system play a leading role. It is conceivable that primary care physicians and hospitals not specializing in hematology become apprehensive with a weekend approaching, and therefore transfer patients at risk at the eleventh hour. In light of this, Friday leukemia might be associated with a poorer outcome. To our surprise (and major relief), overall survival was not statistically different from the group of leukemias presenting on the remaining weekdays in our patient cohort (Figure 1B). In addition, we found no significant differences in the cytogenetic risk group, age, initial leukocyte count, hemoglobin, platelet count, and lactate dehydrogenase.

In summary, our results indicate that Friday leukemia, despite appearing as a discrete disease entity with regard to incidence, failed to demonstrate distinct biologic or prognostic features and was not characterized by impaired survival at our institution. Thus, we hesitate for now to propose the inclusion of this subgroup in the upcoming revision of the World Health Organization classification. Nonetheless, since other medical specialties might also harbor their own specific Friday diseases, we feel that an interdisciplinary effort for further evaluation is clearly warranted.