Isn't Leukemia Still Cancer?
Approaching leukemia today as only a “liquid” cancer in all cases is to overlook knowledge long available about its tumor phenotype.
Leukemia was separated from other cancers in the late 1960s, when effective drugs started to return some leukemic marrows to normal, and patients to normal lives — if only temporarily. No similarly effective drugs existed then for solid tumors not cured surgically.
In 1968, Dr David A. Karnofsky envisioned that a reliable evaluation of tumor drugs would require a “curative approach” to start with mapping out the full extent of every patient's disease using available tests and radiology — and he foresaw the development of metabolic scans for that purpose.1
Although leukemia was known to have the capacity to form “bulky tumors, destructive local infiltrations, and distant metastases,” these observations were forgotten when early success led to anticipation that leukemia, the “liquid” malignancy, would be cured with chemotherapy.
For 50 years, Karnofsky's extent-of-disease workup has been routine in our approach to every solid tumor, lymphoma, and myeloma, and now uses the PET/CT technology he predicted. Leukemia remains the only cancer in which body scanning is not routine, even after an extramedullary tumor is found.
If involvement is isolated to one area, tumor excision or radiation followed by chemotherapy to protect the bone marrow has aborted metastasis and resulted in many lengthy survivals. Yet leukemia's relapse rate remains high, the principal acute leukemia drugs remain those of the 1960s, and the possibility that an occult tumor could explain refractory marrow or minimal residual disease remains inadequately explored.