I believe viral vectors were being tested over 10 years ago, and adenovirus had some favorable characteristics (like being well tolerated and not integrating in the genome). Adenovirus is being used in several researches, including Ziopharm and U of Mich (https://clinicaltrials.gov/ct2/show/NCT01811992).
If anything I would like to see VB-111 dripped into a tumor during surgery (similar to Duke's modified polio virus) and see if that mode of delivery improves effectiveness.