Fluorescent Aided Resection and Evaluation of Soft Tissue Sarcomas (FLARES)

Inclusion Criteria:

* Histological confirmation of any subtype of primary Grades 2 or 3 soft tissue sarcomas (STS), per biopsy evaluation by a pathologist, according to Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC).
* Treatment decision includes planned surgical resection of STS.
* Age ≥18 years at time of consent.
* ECOG Performance Status 0 - 1 (see Appendix)
* Hematology and blood chemistry parameters defined by:

  * Leukocytes ≥ 3 × 109/L
  * Absolute neutrophil count ≥ 1.5 × 109/L
  * Platelets ≥ 100 × 109/L, transfusions may be used to raise platelets to ≥ 100 × 109/L (no washout required)
  * Hemoglobin ≥ 9 g/dL, transfusions may be used to raise Hgb to ≥ 9 g/dL (no washout required)
  * Total bilirubin ≤ 1.5 × institutional upper limit of normal (ULN)
  * Aspartate transaminase (AST) / alanine transaminase (ALT) ≤ 2.5 × institutional ULN
  * Creatinine within normal institutional limits OR creatinine clearance ≥ 30 mL/min/1.73 m2 for patients with creatinine above institutional ULN
* Participants of reproductive potential must agree to using adequate contraception (e.g., hormonal or barrier method of birth control; abstinence, an intrauterine device) for the duration of study participation (including dosing interruptions) and up to 42 days after end of study intervention; or be surgically sterilized (e.g., hysterectomy, tubal ligation, or vasectomy).
* Ability to swallow study agent.
* Ability to understand and willingness to sign an informed consent form.
* Ability and stated willingness to adhere to the study visit schedule and other protocol procedures/requirements for the duration of the study.

Exclusion Criteria:

* Acute/chronic forms of porphyria.
* Uncontrolled, known concurrent illness, including but not limited to ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness.
* Patient has had chemotherapy, tumor resection, or radiation treatment ≤ 21 days prior to surgery.
* Simultaneous participation in another clinical trial ≤ 21 days of enrollment or during the duration of the study period.
* Planned use of other potentially phototoxic substances (e.g., St. John's wort, griseofulvin, thiazide diuretics, sulfonylureas, phenothiazines, sulfonamides, quinolones and tetracyclines), and topical preparations containing aminolevulinic acid (5-ALA) for 24 hours during the perioperative period (defined as 24 hours prior to surgery to up to 24 hours post surgery).
* Pregnant or planning to become pregnant during study participation or breastfeeding.
* Any condition that in the opinion of the investigator would prohibit the understanding or rendering of informed consent or interfere with the participant's safety or compliance while on trial.