The goal of this clinical research study is to learn if the level of nitric oxide you breathe out may relate to the amount of breathing complications that you may experience due to radiation treatment.

Nitric Oxide Breathing Test:

If you agree to take part in this study, you will have a nitric oxide breathing test performed before, during and after radiation therapy. You will you will have a nitric oxide breathing test 1 week before you complete radiation therapy, when you complete radiation therapy, and at each follow-up visit for 6 months.

To complete this test, you will breathe out into a device called a nitric oxide breath analyzer for 10 seconds. You will repeat this test 3 times. The results of this test will give researchers information about possible inflammation in your lungs. The results of this test will be compared with any breathing symptoms you may experience during the same time period.

For your first breath testing session and any session when your nitric oxide level is at least 1 ½ times higher than the first session, you will repeat the test for up to 5 different "breathe out rates". This additional testing will allow the researchers to find where in your lungs the nitric oxide increase is coming from.

Breathing Symptoms Questionnaire:

On the day of each breathing test, you will complete a questionnaire about your breathing and any symptoms you may be experiencing. This should take about 10 minutes. After radiation therapy is complete, some of the monthly questionnaires will be completed by the data coordinator using telephone interviews.

Length of Study:

Your participation in this study will be over after you complete the last breath testing session.

This is an investigational study. The nitric oxide breath analyzer used in this study is FDA approved and commercially available for measuring breathed out nitric oxide levels in patients with asthma. Its use to predict lung inflammation caused by radiation therapy is investigational.

Up to 150 patients will take part in this study. All will be enrolled at MD Anderson.

Inclusion Criteria:

1. Patients will sign consent for the study.
2. Patients with pathologic diagnosis of esophagus or lung cancer.
3. Patient plans to receive radiation treatment at MD Anderson.
4. Patient will receive >/= 5 weeks of thoracic radiotherapy.
5. Patients >/= 18 years of age.

Exclusion Criteria:

1. Patients who have asthma.
2. 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]) must practice effective contraception (oral, injectable, or implantable hormonal contraceptive; tubal ligation; intra-uterine device; barrier contraceptive with spermicide) throughout the study.

Lung and esphageal cancer patients receiving radiation therapy, at UT MD Anderson Cancer Center in Houston, Texas