3. Discussion
Herein, we report a case in which radiation therapy using the Quad Shot
regimen was effective in the treatment of cutaneous metastasis from
parotid gland cancer. The most common sources of cutaneous metastases
have been reported to be breast cancer, colorectal cancer, and melanoma
in women and melanoma, lung cancer, and colorectal cancer in
men.1 Cutaneous metastasis from salivary gland cancer
similar to this case is uncommon.6-8
The optimal treatment of cutaneous metastases has not yet been
established. Wong et al . recommended surgical excision of
metastasis, which would result in a significant decrease in total tumor
burden, improve quality of life, or result in increased
functionality.1 They also indicated that therapy in
patients with widespread unresectable cutaneous and subcutaneous
metastases is limited to other types of palliative therapy such as
radiation therapy, systemic chemotherapy, cryotherapy, laser ablation,
or radiofrequency ablation.
Radiation therapy is an effective treatment method for cutaneous
metastasis. However, its optimal dose and fractionations remain unclear.
Arase et al . reported a case of cutaneous metastasis to the chest
wall from prostate adenocarcinoma. In the case, durable tumor shrinkage
and symptom relief was achieved after radiation therapy using 18 Gy in 3
fractions using electron.9 Oike et al . reported
a case of cutaneous metastasis of non-small cell lung cancer to the arm.
In that case, photon radiation therapy at 45 Gy in 15 fractions led to
complete tumor remission and improved the patient’s quality of
life.3
The Quad Shot regimen, which consisted of 2 days of twice-daily
fractionation with a fraction size of 3.5–3.7 Gy (14.0–14.8 Gy per
cycle) repeated at 3–6-week intervals for a total of three cycles, was
originally devised for advanced pelvic malignancies (RTOG
8502).10 Recently, the Quad Shot regimen has been
successfully adapted for palliative treatment of head and neck
cancer.4,5 The Quad Shot regimen for head and neck
cancer has been reported to achieve a tumor response rates of 53–77%
and palliation rates of over 80% with minimal
toxicity.11 Some reports showed the efficacy of the
Quad Shot regimen for primary skin cancer.12,13However, to the best of our knowledge, there is no report of using the
Quad Shot regimen in patients with cutaneous metastasis.
In this case, cutaneous metastasis was widespread and surgical resection
was difficult. Radiation therapy was administered using the Quad Shot
regimen for extensive cutaneous metastasis of the chest wall. The
treatment resulted in significant tumor shrinkage and relief of symptoms
including exudate and pain. Only grade 1 dermatitis was observed as a
radiation-induced adverse event; no severe adverse events were observed.
Thus, the Quad Shot regimen may be a safe and effective treatment option
for cutaneous metastases.
Some studies have shown that palliative radiation therapy using the Quad
Shot regimen in combination with chemotherapy was effective in symptom
relief and well-tolerated.14,15 In this case,
radiation therapy using the Quad Shot regimen was performed concomitant
with chemotherapy consisting of 5-fluorouracil, cisplatin, and
pembrolizumab. The treatment resulted in favorable symptom relief effect
was and could be safely completed with no serious adverse events.
In conclusion, the Quad Shot regimen may be a safe and effective
treatment option for cutaneous metastases.