Temozolomide treatment duration and secondary hematological neoplasms: A review of the literature and implications for patients with neuroendocrine tumors.

Abstract

510 Background: Evidence-based recommendations for the optimal duration of temozolomide-based treatment in advanced neuroendocrine neoplasms are lacking. Because of the relatively long median survival of NEN and the potential long-term myelotoxicities of temozolomide, suggestions have been made to optimize the duration of temozolomide-based therapy. Here, we have conducted a systematic review of the literature for a descriptive analysis of temozolomide-associated myelodysplasias and leukemias to guide treatment planning. Methods: A database search of PubMed and Embase was conducted to identify case reports and/or case series reporting secondary myelodysplasias or leukemias in the setting of temozolomide therapy. Key data items extracted from the studies were the temozolomide dose and duration, latency to hematologic disorder, type of secondary malignancy and cytogenetics. Reported cases were summarized graphically and descriptively analyzed. Results: A total of 14 studies with 25 patient cases of therapy-related hematologic neoplasms were identified, all of which were case reports or case series. The median treatment duration and cumulative dose were 15 months and 18000 mg/m 2 respectively. Most patients (20/25) were diagnosed on or after 12 months while only one patient was diagnosed before 6 months of treatment. Majority of the patients were diagnosed while still on treatment with temozolomide. Graphically, cases clustered around a cumulative dose of 10,000 to 30,000 mg/m 2 and a latency period of 10 to 40 months which translates to an approximate treatment duration of 12.5 – 37.5 months. Conclusions: Taken together, treatment-related hematologic neoplasms appear to develop beyond the 12-month mark while still on treatment with temozolomide. We suggest an approach to optimizing treatment duration by establishing disease response at 6 months before continuing further treatment and restricting treatment to 12 months or establishing closer vigilance beyond 12 months.