These are rare neuroendocrine tumours arising from the mechanoreceptors of the basal epidermis that are particularly aggressive with a propensity for head and neck and the extremities. Causative factors include exposure to sunlight and immunosuppression. The tumour has many similarities to small cell carcinoma of the lung, with intrinsic sensitivity to radiotherapy and chemotherapy and an aggressive metastatic potential.
- I.A Disease confined to skin and less than 2 cm in diameter.
- I.B Disease confined to skin and more than 2 cm in diameter.
- Involvement of regional lymph nodes.
- III. Metastatic disease.
Surgery is the initial treatment of choice. Most groups advocate a 2 to 3 cm tumour-free margin around the primary lesion when technically possible (no controlled trials comparing different margins), but this is often difficult to achieve in the head and neck region. Many authors recommend postoperative radiotherapy on the basis of retrospective comparison of patients treated with surgery alone with those treated with surgery and post operative radiotherapy 8, 9. The addition of radiotherapy reduced the local failure from 39% to 26% and the regional failure from 46% to 22%. Radiation volumes have included the GTV with generous margins to ensure that the dermal lymphatics surrounding the primary are treated to full dose. The doses used have varied from 45 to 60 Gy, with higher doses being applied to areas of bulky disease.
Treatment of regional draining lymph nodes has been recommended, although prophylactic node dissection or radiotherapy has not shown to influence overall survival. Sentinel node biopsy has been proposed to identify risk of recurrence and minimise need for node dissection.
The presence of distant metastases carries a grave outlook, with median survival being only 9 months. Treatment intent is purely palliative. Radiation can be used to palliate bone and brain secondaries and for advanced cutaneous deposits that are bleeding or fungating.
The role of adjuvant chemotherapy remains undefined. Overall response rates to combination chemotherapy (usually platinum based) for surgically unresectable distant metastatic disease are generally high, although responses are transient.
- Radical: Photons are used depending on depth, site and size of lesion to be treated. PTV=GTV + 3 to 5 cm.
- Radical: 45 to 60 Gy over 5 to 6 weeks (higher doses for residual or bulky disease).
- Palliative: 20 Gy in 5# over 1 week.