A retrospective study by Stern et al., of 1,373 patients concluded that there was an increase in skin cancers in those receiving repeated Goeckerman treatments compared to the control group.[10] This has been refuted by other authors, including Pittelkow et al., who state there has not been an increase in skin cancers among those treated compared to the general population[11] and Menter and Cran, who felt that the Stern study was too crude to have validity and felt a 10-year prospective study would be needed to confirm safety concerns.[5]