Lung Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_33_3643 - Pre-treatment Serum Bicarbonate Predicts for Local Failure after Stereotactic Body Radiation Therapy (SBRT) in Patients with Localized Non-Small Cell Lung Cancer

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Pre-treatment Serum Bicarbonate Predicts for Local Failure after Stereotactic Body Radiation Therapy (SBRT) in Patients with Localized Non-Small Cell Lung Cancer
N. Sebastian1, T. Wu2, X. Mo3, J. G. Bazan1, M. X. Welliver4, K. E. Haglund1, and T. M. Williams1; 1The Ohio State University Wexner Medical Center, Department of Radiation Oncology, Columbus, OH, 2The Ohio State University College of Medicine, Columbus, OH, 3The Ohio State University Wexner Medical Center, Department of Biostatistics, Columbus, OH, 4Department of Radiation Oncology, The Ohio State University Comprehensive Cancer Center, Columbus, OH

Purpose/Objective(s): Tumor hypoxia is known to promote radiation resistance. Tissue oxygenation and acid-base balance are intricately linked and intertwined through complex physiological pathways with oxygen-hemoglobin dynamics, pulmonary vasoconstriction, and cardiopulmonary circulation, all of which could affect oxygen delivery to the pulmonary tumor microenvironment. Although acid-base and respiratory status are ideally ascertained by arterial blood gas, venous chemistries, may be a reasonable surrogate. We hypothesized that relatively high vs low levels of serum bicarbonate (HCO3) could be associated with differential primary tumor control in NSCLC patients treated with SBRT.

Materials/Methods: We retrospectively reviewed outcomes for patients with localized NSCLC treated at our institution between 2008 and 2017. Pre-treatment serum HCO3 was recorded and obtained from the most recent basic metabolic panel (BMP) within 3 months prior to initiation of SBRT. The primary endpoint evaluated was primary tumor failure (PTF), defined as recurrence of the primary tumor. Additional secondary endpoints include overall survival (OS); regional failure (RF), defined as recurrence in regional N1-N3 nodes; and distant metastasis (DM), defined as recurrences outside of the lobe and regional nodes. Cox regression was used to test association between endpoints and pre-treatment serum HCO3, which was dichotomized as high and low by the median.

Results: A total of 117 patients and 122 treated tumors were included. Median follow up was 14.3 months. Males comprised 67.5% (79) of the cohort and females comprised 32.5% (38). Median age was 71 (range 46-92). The majority of tumors were early-stage, with 82 (67.2%) T1 and 29 (23.8%) T2 tumors. A small minority of tumors (7 (5.7%) T3 and 4 (3.3%) T4) were included due to multiple nodules thought to be from the same primary. Adenocarcinomas, squamous cell carcinomas, and undifferentiated/unspecified NSCLC represented 40.2% (49), 51.6% (63), and 8.2% (10) of the cohort, respectively. Median SBRT total dose, dose per fraction, and number of fractions was 50 Gy, 10 Gy, and 5 fractions respectively. Median HCO3 level was 27 mEq/L (range 7 to 43 mEq/L). Univariate cox regression analysis indicated lower serum HCO3 was significantly associated with primary tumor failure (HR=4.09; CI 95% 1.32-12.71, p=.015). PTF at 2 years was 4.4% (CI:1.2%-16.7%) and 24.1% (CI:13.8-40.2%) for high and low HCO3 cohorts, respectively. Median time to PTF was 10.3 and 14.1 months, respectively. There was no association between pre-treatment serum HCO3 and OS, RF, and DM.

Conclusion: Serum HCO3, as measured on a routine BMP, may be a simple, inexpensive biomarker for identifying patients at risk for PTF after treatment with SBRT. These findings necessitate validation using a large, independent cohort.

Author Disclosure: N. Sebastian: None. T. Wu: None. J.G. Bazan: None. M.X. Welliver: None. T.M. Williams: Research Grant; Varian Medical Systems, Inc. Developmental Therapeutics Working Group; NRG Oncology. Co-Leader; National Cancer Institute. Member; National Cancer Institute.

Send Email for Nikhil Sebastian


Assets

TU_33_3643 - Pre-treatment Serum Bicarbonate Predicts for Local Failure after Stereotactic Body Radiation Therapy (SBRT) in Patients with Localized Non-Small Cell Lung Cancer



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Pre-treatment Serum Bicarbonate Predicts for Local Failure after Stereotactic Body Radiation Therapy (SBRT) in Patients with Localized Non-Small Cell Lung Cancer