Inclusion Criteria:

- patients > 18 years of age with primary lung, esophageal or rectal cancer receiving
neo-adjuvant chemoradiotherapy before planned resection

- patients with clinically localized prostate cancer receiving definitive radiation
therapy with external beam treatment. brachytherapy as a boost and/or hormonal
therapy are allowed.

- patients with head and neck, lung, esophageal or cervical cancer who will receive
definitive radiotherapy

Exclusion Criteria:

- prior history of chemotherapy given within 6 months before enrollment.

- prior radiotherapy or radionuclide treatment and/or brachytherapy within 6 months
prior to enrollment.

- unwillingness to comply with tests, protocol, or informed consent.

- concurrent enrollment on any protocol that would require non-compliance with
treatment procedures.

- chemotherapy required within 2 hours following first dose of XRT.

- PET scan done within 48 hours of first blood draw.

- nuclear medicine exposure within 4 days prior to first draw.