The authors of the IMPACT study published in this week's NEJM found no outside variable, including use of the chemotherapy drug Taxotere, explains away the survival difference favoring Provenge. Provenge is priced at $93,000 per course of treatment, which Longo labels as a "concern." "The high cost may affect use. It is also uncertain what role sipuleucel-T Provenge will ultimately play in the treatment of prostate cancer, given the other promising treatments in development," he writes. Longo goes on to mention other prostate cancer drugs in late-stage clinical trials, including Johnson & Johnson's ( JNJ) abiraterone and Medivation's ( MDVN) MDV3100. "The prospects for improved therapy for prostate cancer have never been so encouraging, " Longo concludes at the end of his editorial. "The poor prognosis for men with prostate cancer will probably be substantially improved by the findings that emerge from ongoing clinical research." David Miller of Biotech Stock Research, an independent biotech investment newsletter and a long-time follower of Dendreon, dismissed Longo's arguments as "mostly tired, ignorant or wrong." Meantime, Dendreon will report financial results for the second quarter on Aug. 3. Analysts are expecting Provenge sales of approximately $4 million in the drug's first quarter since launch. -- Reported by Adam Feuerstein in Boston. Follow Adam Feuerstein on Twitter.