2. Case presentation
A 72-year-old man presented to our hospital with a left parotid mass and
cutaneous tumor on the chest wall. The parotid tumor was pathologically
diagnosed as an adenocarcinoma. Additionally, the cutaneous tumor was
considered a metastasis from the parotid gland carcinoma. The tumor
tissues were positive for androgen receptors and human epidermal growth
factor receptor 2 (HER2). Cutaneous metastases spread from the midline
precordium to the left chest and shoulder, accompanied by exudate and
bleeding (Figure 1A). The patient also had edema of the left upper
extremity. Computed tomography showed cutaneous, multiple lymph node
(neck, subclavian, and axilla), and intramuscular metastases (Figure
2A). Upper extremity edema was considered to be due to
axillary/subclavian lymph node metastasis.
Chemotherapy consisting of 5-fluorouracil, cisplatin, and pembrolizumab
administered every 4 weeks (5-fluorouracil:1000 mg/m2, day 1-4;
cisplatin:100 mg/m2, day 1; pembrolizumab:200 mg, day 1) was selected as
the initial treatment. Simultaneously, radiation therapy using the Quad
Shot regimen (2 days of twice-daily fractionation with a fraction size
of 3.5 Gy) was performed for the cutaneous and axillary/subclavian lymph
node metastases with a combination of electrons and X-rays (Figure 3).
Similar radiation therapy was repeated three cycles at 3-week intervals
(Figure 4).
Four weeks after the first Quad Shot, the exudate and bleeding
significantly decreased. As the treatment progressed, the cutaneous
metastases shrank and flattened (Figure 1B, C, D). Computed tomography
showed tumor shrinkage. However, intramuscular metastases outside the
irradiation increased, and a left pleural effusion appeared (Figure 2B).
Grade 1 dermatitis (according to the Common Terminology Criteria for
Adverse Events, version 5) was identified as an acute adverse event of
radiation therapy. Grade 3 leukopenia and grade 1 thrombocytopenia were
determined as chemotherapy-related adverse events. After the second
course of chemotherapy, the patient developed grade 2 pituitary
dysfunction, which was considered an immune-related adverse event caused
by pembrolizumab.
Chemotherapy with 5-fluorouracil, cisplatin, and pembrolizumab was
continued for five courses, but the disease progressed. As second-line
chemotherapy, docetaxel (80 mg every 3 weeks) was started. From the
fourth course, trastuzumab (400 mg every 3 weeks) was added to docetaxel
because HER2 positivity in the tumor was confirmed by dual-color in situ
hybridization. After changing the chemotherapy regimen, a reduction in
tumor lesions was observed. Seven months after treatment initiation, the
irradiated cutaneous metastases remained free of regrowth.