There is continued interest in the use of bevacizumab (Avastin) for treatment of NF2 vestibular schwannomas (VS) due to reports indicating that the drug can reduce the size of these tumors, in some cases sufficient to restore hearing ability. A recent report* on 2 treated individuals from Dr. Victor-Felix Mautner and colleagues in Hamburg, Germany suggests that these effects of Avastin on NF2 VS relies on continued use of the drug; and that once drug treamtent is stopped the tumor will return to its original size. However, it may be possible to obtain continued benefits from Avastin over long periods by i) lowering the dose used and by ii) dosing with the drug at less frequent intervals.
The first individual reported received 5mg/kg every 2 weeks for 1 year then stopped taking drug. During treatment the tumor shrank by over 40% and hearing improved. However 5 months after stopping drug the tumor the tumor had regained 50% of the shrinkage. The individual resumed taking Avastin.
The second individual received 5mg/kg every 2 weeks for 1 year. The tumor shrank significantly but the individual developed hypertension (a side efect of Avastin) during the first year of treatment. The dose was reduced to 70%, and given every 2-3 weeks; then dose was reduced to 50%, snd given every 4 weeks. The tumor has shrunk significantly and remained stable.
Though a report from only 2 individuals, which may not reflect the greater population of those with NF2, these are tremendously interesting observations. They support the idea that Avastin’s main effect is to strengthen blood vessels and thereby reduce edema (therefore volume) in the tumor. This keeps tumor size at bay. The challenge perhaps is to find a low, safe dose of Avastin that can be dosed in an ongoing manner, and introduce further drugs that can target and kill the tumor cells.
* Mautner VF, Nguyen R, Knecht R, Bokemeyer C. Radiographic regression of vestibular schwannomas induced by bevacizumab treatment: sustain under continuous drug application and rebound after drug discontinuation. Ann Oncol.2010 Sep 22. [Epub ahead of print]
