Treatment of Adult Patients With Hemoglobin SC Disease (SCYTHE)

Sickle cell disease (SCD), specifically hemoglobin SC disease (HbSC), is a subtype of sickle cell disease with typically higher hemoglobin and milder or later disease complications. Sickle cell disease is a disorder in which red blood cells (RBCs) are abnormally shaped. This can result in painful episodes, serious infections, and damage to body organs. One medication used to treat sickle cell disease is hydroxyurea.

Hydroxyurea therapy offers significant benefits for infants, children, and adolescents with sickle cell anemia. These include a reduction in the frequency of pain crises and acute chest syndrome (inflammation of the lungs). Hydroxyurea has been given to many HbSC patients but HbSC patients were not included in the large clinical trials used to test hydroxyurea in SCD, so less is known about how HbSC patients respond to hydroxyurea.

The purpose of this research study is to see if hydroxyurea, a medication given to many patients with the most common type of sickle cell, those who are homozygous for the sickle mutation (HbSS), helps individuals who have HbSC. The investigators will see if it helps by giving a questionaire when the medication is started, and then every two months at a clinic visit. The questionaire, called the AdultsQLTM 3.0 Sickle Cell Disease Module, measures quality of life. The investigators will also see how hydroxyurea changes laboratory test numbers, and blood thickness.

Patients will be recruited from the patient population followed at the Texas Children's Cancer and Hematology Centers (TCC/HC)/Baylor College of Medicine (BCM) and the University of Texas Houston Hematology Center. To be eligible to participate in this study, patients must have HbSC disease, have experienced a sickle cell disease related complication, or have a score of 80 or lower on the AdultQLTM Sickle Cell Disease Module 3.0. This questionnaire will be offered to all patients with HbSC seen in our clinic that consent to this study. Patients must also agree to clinic visits every two months, and to phlebotomy, or blood removal after 6 months on the study if they meet criteria for phlebotomy.

If the patient is a sexually active female, they will be offered birth control. If the patient chooses not to initiate effective birth control, they will be tested at their scheduled visit with a urine pregnancy test. If the patient becomes pregnant they will be removed from the study.

Patients will be assessed in clinic every two months after starting treatment. Hydroxyurea will be started at 10 mg/kg/day, and increased by 5 mg/kg/day if needed to a maximum tolerated dose (MTD) of 35/mg/day. The most common side effect of the drug is a drop in infection fighting cells, or white blood cells, so the medication will be started at a low dose and the dose will be increased only if it is safe to do so. After 6 months at MTD on the study, patients will be evaluated for their response to hydroxyurea. If they have not reached their MTD after 6 months their time on the study will be increased to allow for 6 months observation at MTD. The minimum time the patients will be on the study is 12 months after starting hydroxyurea therapy with an option to participate in a 2 year observation study following the end of the study.

If the patients have had minimal or no benefit from the medication, monthly phlebotomy will be added to their treatment regimen, at 7-10 ml/kg. The first phlebotomy volume will be 7 ml/kg, but may be increased to 10 ml/kg to obtain the target Hb of 9-10 g/dL. Patients will remain on hydroxyurea and phlebotomy for six months. If their Hb is less than or equal to 9.0 g/dL on their phlebotomy visit, phlebotomy will not be performed and their phlebotomy visits will be spaced every 2 months. Patients time on the study will be increased to allow for 6 months observation to ensure that there is no late harmful effects. The minimum time patients will be on the study is 18 months after starting phlebotomy with an option to participate in a 2 year observation study following the end of the study.

Patients will be asked to allow the investigators to review information from their medical records at the start of the study, and throughout the study. If the patient would like to participate in the two year follow-up, their records will be reviewed during that period as well.

Eligibility Criteria:
Inclusion Criteria:

* Diagnosis of HbSC disease
* Score of 80 or lower on the AdultQLTM 3.0 Sickle Cell Disease Module, or any disease related complication, including, but not limited to, one or more pain events per year, proliferative sickle retinopathy, avascular necrosis, cholelithiasis, or any thrombotic event. If the subject has a score \>80, they may still enroll on the trial, and be analyzed for secondary endpoints. They will be excluded from analysis of the primary endpoint.

Exclusion Criteria:

* Failure to meet inclusion criteria
* Hydroxyurea usage in the last 3 months.
* Chronic RBC transfusion therapy
* Packed red blood cell transfusion in the last 3 months (temporary exclusion).
* Pregnancy, or refusal to use medically effective birth control if female and sexually active.
* Current phlebotomy therapy