The goal of this clinical trial is to investigate the effectiveness of Methylene Blue (MB) as a radiosensitizer in treating head and neck squamous cell carcinoma (HNSCC) that has recurred locally and is resistant to radiation therapy. It will also assess the safety of Methylene Blue. The main questions it aims to answer are:

Does Methylene Blue improve the outcomes for patients with recurrent HNSCC receiving radiation therapy? What side effects do participants experience while receiving Methylene Blue?

Participants will:

Receive weekly injections of Methylene Blue or placebo into the tumor over six weeks.

Undergo six weeks of concurrent radiation therapy. Be monitored regularly for treatment effects and document any side effects experienced during the trial.

This single-center clinical trial intends to recruit 10 eligible patients diagnosed with locoregional recurrence of HNSCC that is resistant to previous radiotherapy.

Inclusion Criteria:

1. . Histologically confirmed squamous cell carcinoma of head and neck.
2. . Locoregional recurrence.
3. . After standard treatment of R/M HNSCC.
4. . Measurable disease. Defined as presence of at least one lesion as being ≥10 mm in at least one dimension measured with conventional computed tomography (CT) or ≥10 mm in at least one dimension measured with spiral CT scan or magnetic resonance imaging (MRI).
5. . Lesion selection criteria - at least 1 lesion to be injected must be measurable and greater than or equal to 1.5 cm and longest diameter not exceed 10 cm in principle.
6. . ECOG performance status ≤2.
7. . Age ≧20 years old; and life expectancy of at least 12 weeks.
8. . Prior treatments with radiation therapy for palliative management of non-target lesion metastatic disease is permitted provided that at least 2 weeks have elapsed since the last fraction of radiation therapy, disease progression has been documented and all treatment related adverse events are ≦ grade 1 at the time of registration.
9. . Must not have received anticancer therapy used with an antineoplastic intent, including chemotherapy, immunotherapy, biologic, or any investigational therapy within 14 days prior to the first dose of study drug.
10. . No history of allergic reactions attributed to methylene blue.
11. . Patient consent must be obtained.
12. . Negative pregnancy test, Fertile patients must use effective contraception.

Exclusion Criteria:

1. . Presence of central nervous system (CNS) metastases.
2. . The organ function measured within 14 days prior to study entry as defined below: Absolute neutrophil count (ANC) less than 1,000/mm3, or platelets less than 100,000/mm3; serum bilirubin greater than 1.5 times the upper limit of normal range (ULN); alanine aminotransferase (ALT) or aspartate aminotransferase (AST) greater than 2.5 times the ULN if no demonstrable liver metastases, or greater than 5 times the ULN in the presence of liver metastases; creatinine clearance ≤40 ml/min.
3. . Concomitant illness including uncontrolled infection or other active, uncontrolled disease such as congestive heart failure, angina pectoris, respiratory insufficiency, and arrhythmia.
4. . Documented hypersensitivity to methylene blue compound or compounds of similar chemical or biologic composition.
5. . Pregnant or lactating women.