As the saying goes, "if at first you don't succeed, try, try again." Genentech (NYSE:DNA) is doing just that, announcing Friday its second attempt to gain FDA approval to use its cancer antibody Avastin as a treatment for breast cancer.

In September of last year, the FDA issued an "approvable letter" after Genentech's first attempt, citing the need for an independent review of the company's statistical results from a 722-person phase 3 study. The company now has that review. An FDA response to the application is expected within six months.

Most oncology-related studies have progression-free survival results independently reviewed as the variables determining whether a patient's cancer has spread can be somewhat subjective and open to interpretation.

While there surely is much better drama to tell than Genentech did publicly, it claims that the FDA initially "communicated" that it was OK with how Genentech counted its progression-free survival (PFS) statistics in its initial marketing application, but then changed its opinion following the review of the potential label-expanding application.

Avastin helps cancer patients by targeting a part of cancer cells that is crucial for the disease to grow. It has the potential to be used in a wide variety of cancers and has become a blockbuster compound with sales of $1.7 billion in the U.S. last year. It is currently approved to treat non-small cell lung cancer and colorectal cancer, where it competes with compounds like ImClone Systems' (NASDAQ:IMCL) Erbitux. 

Whatever the outcome of the Avastin marketing application, Genentech's saga with the FDA serves as a reminder of the fickle nature of the government agency and how often the agency baffles investors and drugmakers with its decisions. It's also important to keep in mind that some unscrupulous drugmakers like to blame the agency for their mistakes or dishonest actions. Genentech is without a doubt not one of those drugmakers, so it deserves a pass for the delayed timeline in getting Avastin on-label approval to treat breast cancer.

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Fool contributor Brian Lawler does not own shares of any company mentioned in this article. The Fool has a disclosure policy.