The goal of this clinical research study is to learn if the radiation that you will receive for esophageal cancer may cause the heart to create more proteins called cardiac biomarkers.

When cardiac biomarkers are above normal levels, there may be heart damage. The relationship between cardiac biomarkers and radiation therapy has not been well studied. Learning more about this relationship may lead to better ways to check the heart during radiation therapy and predict heart problems.

If you are found to be eligible and you agree to take part in this study, you will have baseline tests. The following tests and procedures will be performed within 1-2 weeks from the start of radiation:

• You will be asked about any other health problems you may have.
• Your performance status will be recorded.
• Blood (about 2 teaspoons) will be drawn for routine tests.
• Blood (about 1 teaspoon) will be drawn to measure cardiac biomarkers.
• You will have an electrocardiogram (ECG) to check your heart function.
• If the study doctor thinks it is needed, you will have an exam by a cardiologist (a doctor who diagnoses and treats heart problems) who will check the results of your ECG.

Study Visits:

Blood (about 1 teaspoon) will be drawn to measure cardiac biomarkers at the following time points:

• Within 12-24 hours of the start of radiation
• One (1) time during the third week of radiation
• Within 48 hours after completion of radiation

Follow-Up:

About 1 to 2 months after you complete radiation therapy, depending on when you and your doctor decide, you will return to the clinic. The following tests and procedures will be performed:

• Blood (about 1 teaspoon) will be drawn to measure cardiac biomarkers.
• You will have an ECG.

Length of Study Participation:

You will be off study after your follow-up visit.

You will no longer be able to take part in the study if the disease gets worse, if intolerable side effects occur, or if you are unable to follow study directions.

This is an investigational study. Using cardiac biomarkers to check the heart during radiation therapy to predict future heart problems is considered investigational.

Up to 100 patients will be enrolled in this study. All will be enrolled at MD Anderson.

Inclusion Criteria:

1. Patients with histologically proven esophageal cancer to be treated with RT with concurrent chemotherapy to a final dose of >/=40 Gy will be included in this study.
2. Patients with mid thoracic, distal esophageal, and gastroesophageal junction tumors.
3. All patients must sign a study-specific informed consent form. If the patient's mental status precludes his/her giving informed consent, written informed consent may be given by the patient's legal representative.
4. Age >/= 18
5. Women of childbearing potential (A woman of child-bearing potential is a sexually mature woman who has not undergone a hysterectomy or who has not been naturally postmenopausal for at least 24 consecutive months [i.e., who has had menses at any time in the preceding 24 consecutive months]. For women of childbearing potential, a blood pregnancy test must be performed within 72 hours prior to the start of protocol treatment.
6. Induction chemotherapy allowed.
7. Being able to meet radiation dose constraints of at-risk organs.

Exclusion Criteria:

1. Patients who receive cardiotoxic drugs, such as trastuzumab or adriamycin as part of their chemotherapy regimen.
2. Patients with recent myocardial infarction in the past month, decompensated heart failure or myocarditis/pericarditis in the past month.
3. Patients with renal failure indicated by a glomerular filtration rate (GFR) < 30 mL/min/1.73sq.m.
4. Patients in the intensive care unit (ICU).
5. Patients with systemic sepsis.
6. Patients with acute pulmonary embolism in the past month.
7. Women who are pregnant or nursing are not eligible as treatment involves unforeseeable risks to the fetus or child.
8. Inability to obtain histologic proof of malignancy.
9. Patients with proximal / cervical esophageal cancer.

Patients with histologically proven esophageal cancer to be treated with radiation therapy with concurrent chemotherapy to a final dose of >/=40 Gy included in this study at UT MD Anderson Cancer Center in Houston, Texas.