Optical coherence tomography and quantitative optical imaging of brain cancer

Surgery is an essential component of brain cancer management. Glioma is the most common adult primary brain cancer, with inevitable recurrence and fnite survival times (Stupp et al. 2005; McGirt et al. 2008, 2009; Chaichana et al. 2010a, b, 2012). While glioma treatment consists of a combination of surgery, radiation, and chemotherapy, surgery remains the frst-line therapy and the most common initial step for glioma treatment. Recent studies have consistently demonstrated the signifcant long-term benefts of safe, maximum cancer resection, including improved overall surgical and delayed cancer recurrence for both low-grade and high-grade gliomas (Karim et al. 1996; Sanford et al. 2002; Laws et al. 2003; Stummer et al. 2006; McGirt et al. 2008, 2009; Smith et al. 2008; Chaichana et al. 2011, 2012, 2013a, b, 2014; Sanai et al. 2011; Jakola et al. 2012; Markert 2012; Chaichana and Quinones-Hinojosa 2013, 2014; Almeida et al. 2015). Currently, the surgical paradigm is to resect as much cancer as possible, while avoiding new neurological defcits and preserving critical neurological functions such as motor function and speech. As recent studies have elucidated, the surgical extent of resection (EOR) is critical in prolonging progression-free and overall survivals for high-grade glioma patients (Laws et al. 2003; Stummer et al. 2006; McGirt et al. 2009; Chaichana et al. 2011, 2012, 2013a, b, 2014; Sanai et al. 2011; Chaichana and Quinones-Hinojosa 2013, 2014; Almeida et al. 2015). Sanai et al. conducted a systematic study with 500 glioblastoma (i.e., GBM, or high-grade glioma) patients and reported signif-cant improvements in survival for patients with ≥78% EOR (Sanai et al. 2011); furthermore, GBM patients with gross total resection had a 1.6-fold increase in survival when compared with patients with subtotal resection. Similarly, Chaichana et al. reported a 70% EOR threshold that is associated with increased progression-free and overall survivals and that every 5% increase in resection decreases the risk of death by 5.2% for glioblastoma patients (Chaichana et al. 2013a). Finally, the same trend can be found in low-grade glioma patients. Of the patients with low-grade glioma, 50%-75% die from recurrence or progression to a malignant (i.e., higher grade) glioma (Keles et al. 2001). Maximal EOR in low-grade glioma is also signifcantly associated with improved survival and delayed recurrence (Karim et al. 1996; Sanford et al. 2002; McGirt et al. 2008; Smith et al. 2008; Jakola et al. 2012; Markert 2012). Berger et al. demonstrated that patients with a residual tumor volume of less than 10 cm³ have a progression-free survival when compared with patients with >10 cm³ residual tumor volume (50 vs. 30 months) (Berger et al. 1994); similarly, McGirt et al. have reported that gross total resection is associated with increased overall survival and progression-free survival (when compared with subtotal resection); similarly, Smith et al. reports that a >90% EOR (vs. <90% EOR) is associated with over 50% increased overall survival at the 5-8-year time points (McGirt et al. 2008; Smith et al. 2008). In summary, surgery is critical to brain cancer management and there is a clear clinical need to maximize cancer resection, which delays recurrence, improves response to adjuvant therapies (such as chemotherapy and radiation treatments), and increases survival. The tools used in the operating room (OR) are evolving, and in this review, we discuss the present and future adjuvant tools that will aid the surgeon in maximizing resection while preserving maximal function, so that the patients can enjoy the survival benefts in increased resection and achieve a high quality of life.