This clinical trial tests the feasibility, best dose, and effectiveness of L-theanine for supporting relaxation and mood among cancer patients in surveillance. L-theanine is a substance found in the leaves of green tea with potential to enhance mental health and well-being. It works by increasing certain chemicals within the body that have been associated with stress reduction, mood stabilization, and improved cognitive performance.

PRIMARY OBJECTIVES:

I. To determine the feasibility of L-theanine use among cancer patients in surveillance based on adherence.

II. To determine the relationship of L-theanine on relaxation and supporting mood among cancer patients in surveillance with a dose of 200mg once daily versus (vs) twice daily, as measured by Visual Analog Scale-Relaxation (VAS-R).

SECONDARY OBJECTIVES:

I. To observe the relationship of L-theanine in reducing anxiety among cancer patients in surveillance, as measured by Visual Analog Scale-Anxiety (VAS-A).

II. To observe the relationship of L-theanine on mood states as measured by Short Form of the Profile of Mood States (POMS-SF).

EXPLORATORY OBJECTIVES:

I. To determine the feasibility of L-theanine use among cancer patients in surveillance based on recruitment.

II. To observe the relationship of L-theanine in supporting sleep among cancer patients in surveillance as measured by the Pittsburgh Sleep Quality Index (PSQI).

III. To describe the side effects of L-theanine supplementation. IV. To observe the relationship between L-theanine on symptom burden among cancer patients in surveillance as measured by Edmonton Symptom Assessment Scale (ESAS).

OUTLINE: Patients are randomized to 1 of 2 arms.

ARM I: Patients receive L-theanine orally (PO) once daily (QD) for 6 weeks in the absence of unacceptable toxicity.

ARM II: Patients receive L-theanine PO twice daily (BID) for 6 weeks in the absence of unacceptable toxicity.

After completion of study intervention, patients are followed up at 14 days.

Inclusion Criteria:

• Documented informed consent of the participant and/or legally authorized representative.

  • Assent, when appropriate, will be obtained per institutional guidelines

• Willingness to comply with all study interventions including the use of L-theanine and follow-up assessments

• Age: ≥ 18 years

• Ability to read and understand English or Spanish for questionnaires

• Patients must be a cancer patient who has completed treatment and has been in surveillance for at least 6 months

• Participants must not have used any herbs or supplements in the past 30 days

• Participants must report an anxiety score of > 3 on Visual Analog Scale - Anxiety

• Participants must not have had any changes to their psychiatric medications within the past 60 days

• Women of childbearing potential (WOCBP): negative urine or serum pregnancy test. If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required

• Agreement by females and males of childbearing potential to use an effective method of birth control or abstain from heterosexual activity for the course of the study through at least 1 month after the last dose of protocol therapy.

  • Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for > 1 year (women only)

Exclusion Criteria:

• Concurrent use of other alternative medicines, including herbal agents and high-dose vitamins and minerals, unless taken to correct a documented vitamin or mineral insufficiency
• Chemotherapy, radiation therapy, biological therapy, immunotherapy, or any other systemic treatment excluding hormonal therapy (must be on a stable dose of hormonal therapy for at least 60 days)
• Any patients taking bortezomib, as L-theanine can decrease effectiveness
• Any patients currently enrolled in other clinical trials that might interfere with the results of this study
• History of allergic reactions attributed to compounds of similar chemical or biologic composition to study agent
• Any patients with an ongoing active/unstable psychiatric condition, depressive/bi-polar related disorders, anxiety, psychosis disorders, or substance use that may interfere with the ability to participate in the study as outlined in the study procedures section of the protocol
• Any patients with chronically unstable blood pressure or chronic low blood pressure
• Diagnosis of Gilbert's disease
• Females only: Pregnant or breastfeeding
• Any other condition that would, in the Investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
• Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)