Advances in the Treatment of LEUKEMIA
Thanks to advances in pharmaceutical treatment and other research, the survival rate of people with leukemia has tripled in the last 40 years.
In leukemia, the bone marrow produces abnormal white blood cells—the leukemia cells, which in time may crowd out normal white blood cells, red blood cells, and platelets. Types of leukemia vary according to which type of blood cells are affected, how developed the cancer cells are at the time of diagnosis, and how different they are from normal cells.151 According to the National Cancer Institute, there were 30,600 new cases of leukemia in the United States in 2003.152
Patient Perspective: The Wave of the Future Brings Hope
Ancient Medicinal Offers New Hope to Young Adults
Contrary to images people may conjure up when hearing "arsenic," it actually has given new hope to patients with acute promyelocytic leukemia (APL), which is most common in young adults and causes fatigue and tendency to bleed. Arsenic-containing preparations, dating back more than 2,000 years, were used more than 100 years ago for leukemia therapy but were replaced by modern chemotherapy. Because some Chinese arsenic-containing treatments showed effectiveness against leukemia, attention again turned to arsenic."153
Arsenic trioxide was approved in 2000 to treat APL patients whose disease has recurred or failed to respond to standard treatment (about 400 of the 1,500 diagnosed cases per year).154 About 75 percent of APL patients can be cured with other combination therapies, but those who do not achieve remission or who relapse can now be treated with arsenic trioxide.155
From Texas Soil to New Class of Anticancer Therapy
The story of gemtuzumab began with a soil sample gathered in Kerrville, Texas, in 1981 and finally burst to the forefront of oncology in 2000 as the first in a new class of drugs, "antibody-targeted chemotherapy." Scientists studying the soil discovered a powerful cancer-fighting substance, calicheamicin, which destroyed the DNA of cancer cells and proved to be stronger than any anticancer drugs at the time. But it was up to 10,000 times more toxic to normal cells than other anticancer drugs. Researchers discovered that by attaching calicheamicin to an antibody (immune system protein), they could safely bring it directly to the tumor, bypassing most normal cells. In May 2000, the FDA approved the first antibody-targeted chemotherapy, gemtuzumab, for use in patients over age 60 with relapsed acute myeloid leukemia (AML).
In patients with AML, unhealthy white and red blood cells and platelets build up in the bone marrow, blood, and other parts of the body leading to infections, easy bleeding, and anemia. AML quickly worsens if not treated.156 It is estimated that in 2005, 11,960 cases of AML will be diagnosed and will cause 9,000 deaths.157 Gemtuzumab was found to cause remission in about 30 percent of AML sufferers and produces fewer side effects than traditional chemotherapies.158
A Powerful Attack and a True Trailblazer
The approval of imatinib mesylate in 2001 proved that a targeted therapy—one that directly turns off the signal of a protein known to cause cancer—could powerfully attack cancer with few side effects.159 Imatinib not only benefits patients with chronic myeloid leukemia (CML), but its success proves that the targeted therapies scientists dreamed of do work. With this proof-of-concept, scientists may be able to create strong, effective targeted therapies for other cancers. Clinical trials showed imatinib's remarkable efficacy, as most patients receiving the new drug were experiencing complete normalization of their blood counts.160
In patients with CML, the bone marrow produces too many stem cells which develop into a type of white blood cell called granulocytes. Some of these cells never become mature white blood cells; these are called blasts. Over time, the granulocytes and blasts crowd out the red blood cells and platelets in the bone marrow. CML usually occurs in middle-aged or older adults.161 It is estimated that 4,600 new cases of chronic myeloid leukemia will be diagnosed this year, and 850 people will die from the disease.162
First For-Kids-Only Leukemia Drug in 10 Years
For 10 years, oncologists treating pediatric patients with acute lymphoblastic leukemia (ALL) treaded water as therapy for the most common childhood leukemia had hit a plateau.163 Finally, the 2004 approval of clofarabine presented a new option for children aged 1 to 21 with ALL who had relapsed or were unresponsive to other treatments. Clofarabine produces remissions and allows some patients to proceed to bone marrow transplant, the best chance for long-term survival.164
About 3,830 Americans are diagnosed with ALL, the most common type of leukemia in patients under age 19, each year.165 In ALL, abnormal blood cells called lymphoblasts accumulate, while fewer normal red and white blood cells are produced.
Clofarabine is an antimetabolite, a drug that prevents cancer cells from growing by disrupting the synthesis of nucleic acids, which are needed to produce DNA and RNA.
One in every 10 individuals in this country has received a diagnosis of a
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151 C. Lewis, "Living with Leukemia," FDA Consumer Magazine (March-April 2002), http://www.fda.gov/fdac/features/2002/202_leuk.html (accessed 27 September 2005).
152 National Cancer Institute, SEER Cancer Statistics Review, 1975-2000 (2003), http://seer.cancer.gov/csr/1975_2000 (accessed 27 September 2005).
153 Food and Drug Administration, "FDA Approves Arsenic Trioxide for Leukemia Treatment in Record Time for a Cancer Drug Development Program," 26 September 2000, http://www.fda.gov/bbs/topics/ANSWERS/ANS01040.html (accessed 25 July 2005).
154 Food and Drug Administration, Consumer Drug Information: Trisenox®, http://www.fda.gov/cder/consumerinfo/druginfo/Trisenox.HTM (accessed 27 September 2005).
155 "Definition of Acute promyelocytic leukemia, MedicineNet.com, http://www.medterms.com/script/main/art.asp?articlekey=19758.
156 National Cancer Institute, "General Information About Adult Acute Myeloid Leukemia," National Cancer Institute, http://www.nci.nih.gov/cancertopics/pdq/treatment/adultAML/patient (accessed 4 August 2005).
157 American Cancer Society, Inc., "Overview: Leukemia—Acute Myeloid. How Many People Get Acute Myeloid Leukemia?" American Cancer Society, http://www.cancer.org/docroot/CRI/content/ (accessed 26 August 2005).
158 Pharmaceutical Research and Manufacturers of America, "Innovator Stories," Innovation.org, http://www.innovation.org/microsite/people_health/innovator_stories_mylotarg.htm (accessed 27 September 2005).
159 National Cancer Institute, "Gleevec," National Cancer Institute, http://www.cancer.gov/clinicaltrials/digestpage/gleevec (accessed 27 September 2005).
160 Novartis Pharmaceuticals Corporation, Prescribing Information, Gleevac®, http://www.pharma.us.novartis.com/product/pi/pdf/gleevac_tabs.pdf (accessed 20 January 2006).
161 National Cancer Institute, "General Information About Chronic Myelogenous Leukemia," http://www.nci.nih.gov/cancertopics/pdq/treatment/CML (accessed 4 August 2005).
162 American Cancer Society, Inc., "Detailed Guide: Leukemia—Chronic Myeloid (CML): What Are the Key Statistics About Chronic Myeloid Leukemia (CML)?" American Cancer Society, http://www.cancer.org/docroot/CRI/ (accessed 26 August 2005).
163 Genzyme, "First Leukemia Drug Approved Initially for Children in More Than a Decade," press release, 29 December 2004, http://www.genzyme.com/home/search_corp_results.asp (accessed 5 October 2005).
164 Genzyme Corporation, Prescribing Information, Clolar®, http://www.fda.gov/cder/foi/label/2004/021673lbl.pdf (accessed 20 January 2006).
165 Leukemia & Lymphoma Society, "Acute Lymphocytic Leukemia," Leukemia & Lymphoma Society, http://www.leukemia-lymphoma.org/all_page?item_id=7049 (accessed 27 September 2005).
166 National Organization for Rare Disorders, http://www.rarediseases.org./info/about.html.
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