Does Volumetric Resection Matter in Non-functioning Macroadenomas?

Introduction: Resection volume has a statistically significant survival advantage in gliomas. It has been observed in pituitary macroadenomas (PMA), especially large tumors, that endoscopic resection offers an advantage to resect more tumor than microscopic approaches. However, it is not known whether increased resection leads to a reduction in additional treatments long-term or outcome. Therefore, we assessed whether volumetric resection impacted further treatment in a cohort of patients with prolonged follow-up.

Methods: Electronic records were reviewed from 1997–2008 for patients with PMA that were either null cell or non-secreting and greater than 2cm. Inclusion criteria were at least four years of follow-up (unless there was recurrence prior to four years) and pre and postoperative MRI available for review. We specifically used an older cohort of only microscopic cases so the treatment was uniform and recurrence would likely be observed in the time period. Ninety-seven patients met inclusion criteria, all of whom underwent maximally safe resection as treatment intent. Collected data included patient characteristics, MRI measurements, adjuvant treatment, subsequent growth and treatment, and follow-up. All MRI calculations were performed by a board-certified neuro-radiologist. Volume was calculated by the following formula: 4/3*π*axial cm*coronal cm*sagittal cm= cm3. Percent resected volume(PRV) was also calculated. A gross-total resection (GTR) was defined by absence of definite tumor on post-operative imaging. Statistics included Chi-squared, t-test, and uni- and multivariate logistic regression.

Results: Mean age was 56.5 ± 13.9(19–85); sixty-nine(70%) were male. Median follow-up was 113(30–207) months. Sixty patients(61%) had no tumor growth at a median time of 106.5(48–203)months; 32 had GTR and 28 STR. Eleven(11%) patients had planned adjuvant radiation; none had tumor growth. Thirty-seven(43%) patients had recurrence or tumor growth with a median time of 43(8 –110)months; 9 patients had GTR and 28 STR. Four patients were observed. Treatment(n = 33) included confocal field radiation(n = 5), gamma knife radiosurgery(n = 19), and repeat surgery(n = 9).

Comparing patients that had no further treatment(n = 64) versus treated growth(n = 33), there was a statistically significant differences in age[mean 59.1 ± 14.2(19 –85)v51.6 ± 12.2(20–74),p = 0.012], but not sex or Knosp-Steiner grades. The mean preoperative and postoperative volumes were 667.0 ± 681.5 (551.2–4063.0) v 741.9 ± 558.3 (140.5–2804.7) cm³ and 116.0 ± 367.8 (0–2816.6) v 121.7 ± 133.5 (0–464.9) cm³, respectively (p > 0.05), while PRV was 89.7 ± 17.6 (22.2–100)% v 79.8 ± 21.4 (8.1–100) % (p = 0.015). On univariate analysis, sex, Knosp-Steiner grade, preoperative and postoperative volumes were not statistically significant. Age [OR: 14.9 (95% CI: 1.83–148.4), p = 0.015] and PRV [OR: 13.9 (95% CI: 1.6–150.4), p = 0.017] were statistically significant and remained significant on multivariate analysis [age OR: 13.0 (95% CI: 1.5–134.6), p = 0.023); PRV OR 10.1 (95% CI: 1.3–152.5), p = 0.028]. Examining only patients that had subtotal resection, percent resection was not significant for tumor growth on univariate analysis [OR: 2.77 (95% CI: 0.2–39.2), p > 0.05].

Conclusion: Volumetric resection was significant in the entire cohort when including patients with both GTR and STR, but was not significant in patients with only STR. This difference could be due to the approximating formula instead of a more exact volumetric analysis or a larger cohort is needed to detect a difference. Surgeons able to achieve gross total resection resulted in fewer future treatments in this cohort. However, given the effectiveness of adjuvant treatments, those with residual tumor are well-treated when aggressive maximally safe resection is practiced.