Study of Nab-Paclitaxel in High Risk Early Breast Cancer

The Norton-Simon-Hypothesis on log cell kill suggests that chemotherapy should be given at maximum dosages at minimum intervals. Combination chemotherapy, which always has to make compromises regarding the doses of each drug and treatment intervals due to acute as well as cumulative toxicities, does therefore not comply with this theory. Sequential application of monotherapies, however, allows very high single agent doses and dose-dense treatment intervals. Regimens designed according to the Norton-Simon-Hypothesis have shown to be highly active as adjuvant treatment for early breast cancer. As the number of cycles of each agent can be restricted to 3, as previously done in the AGO ETC trial by Möbus et al., cumulative toxicities do not really occur. Two large scale trials of dose-dense chemotherapy have proven very high protective activity against tumor recurrence (AGO ETC (Ref.1) and CALGB 9741 (Ref.2)). Especially the ETC trial (epirubicin, solvent-based paclitaxel, and cyclophosphamide) showed an impressive superior DFS and OS in 1284 high-risk breast cancer patients with \> 4positive lymph nodes. The doses used are exceptional at maximum dosage and minimum intervals with epirubicin 150 mg/m², Paclitaxel 225 mg/m² and cyclophosphamide 2.5 g/m² given every 2 weeks based on the above described Norton-Simon-Hypothesis. However, as each drug was given only 3 times at intervals of 2 weeks, this regimen is feasible and safe with primary support of G-CSF and ESF. The ETC schedule is today considered standard of care for high-risk breast cancer patients in Germany. However, both trials, ETC and CALGB 9741, compared the dose-dense concept against EC-P q3w which is nowadays considered to be an inferior regimen compared to EC-P weekly or EC-Doc. The GAIN trial had a 2x2 factorial design and explored ETC versus EC-TX and ibandronate vs. observation. The trial closed recruitment after 3023 pts in July 2008. In the Panther trial, a joint effort of SBG, ABCSG, AGO-B and GBG, the tailored, dose-dense EC-Doc (dtEC-dtD) regimen was tested against conventional dosed FEC-Doc. Efficacy results are to be awaited, safety results will be published in 2012. Nab-paclitaxel (nP) provides a better toxicity profile and a higher efficacy compared to solvent based taxanes (paclitaxel and docetaxel). It might therefore be the preferred component in an intense dose-dense regimen. Assuming that the corresponding dose of nab-paclitaxel to 175 mg/m² paclitaxel is 260 mg/m², an appropriate dose would be 330 mg/m² nab-paclitaxel to substitute paclitaxel at 225 mg/m². So far, no experience with such a dose of nab-paclitaxel is available. However, initial experience with 300mg/m² q3w and 150mg/m² weekly (in 3 out of 4 weeks) showed a good safety profile even when given for a median of 8 cycles (Ref.3). Another pilot study showed a good tolerability of 260 mg/m² nab-paclitaxel given q2w for 4 cycles (Ref.4+5). The GAIN-2 trial will allow for comparing the toxicity and effectiveness of a predefined intense dose-dense regimen (EnPC) vs. a dose-dense regimen with modification of single doses depending on individual haematological and non-haematological toxicities. The primary aim of the GAIN-2 trial will be to compare the invasive disease-free survival after adjuvant chemotherapy with EnPC or dtEC-dtD in patients with primary node-positive or high risk node negative breast cancer. To explore the maximum dose of nab-paclitaxel in this setting, a run-in phase with varying doses of nab-paclitaxel is included in the study design.