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Adequate adjuvant radiation therapy dose found for Merkel cell carcinoma

Patients with Merkel cell carcinoma experienced satisfactory overall survival results following an adjuvant radiation therapy dose ranging from 40 Gy to lower than 50 Gy.

Researchers conducted a retrospective review of 2,093 patients identified using the National Cancer Database. The patients had stage I to stage III Merkel cell carcinoma of the extremities and/or trunk, and had been treated between 1998 and 2011.

Radiation doses were categorized by dose, with a range of 30 Gy to < 40 Gy; 40 Gy to < 50 Gy; 50 Gy to 55 Gy; or > 55 Gy to 70 Gy.

Overall survival served as the primary outcome measure. The median follow-up duration was 37 months.

There were 904 deaths reported during follow-up.

Results indicated a 3-year overall survival rate of 41.8% for the lowest radiation therapy dose group, compared with 69% for the second group, 69.2% for the third group, and 66% for the highest dose group (omnibus P < .001).

The researchers compared overall survival for patients in the 50 Gy to 55 Gy arm with those seen in the 40 Gy to < 50 Gy group and found that they were equivalent (adjusted HR = 0.89; P = .52). Overall survival was also equivalent for the 50 Gy to 55 Gy dose and the > 55 Gy to 70 Gy dose (adjusted HR = 1.18; P = .17), but worse for the > 30 Gy to < 40 Gy dose when compared with the > 55 to 70 Gy dose (adjusted HR = 2.63; P < .001). – by Rob Volansky

Disclosure: The researchers report no relevant financial disclosures.