A New Way to Assess Dynamic Response of Centrally Located Lung Cancer (CLLC) to SBRT and Conventional Radiation Therapy (CRT) šŸ“

Author: Nina Burbure, Tawfik Giaddui, Shidong Li, Curtis Miyamoto, Jeremy Price, Bin Wang šŸ‘Øā€šŸ”¬

Affiliation: FCCC at Temple University Hospital, Dept. of Radiation Oncology, Fox Chase Cancer Center at Temple University Hospital šŸŒ

Abstract:

Purpose: Higher rates of local failures and toxicities challenged radiation therapy of centrally located lung cancer (CLLC). We assessed the treatment response by measuring the early changes of PET+ nodule or mass (GTV) and surrounding targeted volume (PTV) during and after fractionated treatments to correlation with clinical outcomes and biological modeling.

Methods: Daily or weekly cone-beam CTs and/or follow-up chest CTs of patient with PET+ or biopsy-approved nodular GTVs ranged from 0.5 to 24 cc undertaking SBRT and massive GTV ranged from 2 to 1027 cc undertaking CRT were deformably co-registered with plan CT at the lung window & level settings using a commercial software. Reciprocal of GTV (or PTV) were linearly fitted as 1/GTV = aƗT + b to determine the half time T1/2 = (2-b)/a. This response time were categorized to small cell lung cancer (SCLC), squamous carcinoma (SqC), adenocarcinoma (AdC), and non-small-cell lung cancer (NSCL). Survival curves of each cell lines and patient-derived organoids was modeled for EQD2 calculation.
Results: T1/2 for CRT of SqC /SCLC GTVs and SBRT of NSCL GTVs were 3 and 4 months, respectively. Large AdC and NSCLC GTV undergone CRT and small AdC GTV undertaking SBRT had negative T1/2 or tumor growing during or post treatment. Except for large NSCL PTVs with smallest T1/2 of 1 month, most other PTVs had either large positive or negative T1/2 for slow shrinking or growing.
Conclusion: The response half times of GTV and PTV (overlapped the OARs for toxicity evaluation) demonstrated patient-specific response and large variations among different morphological cancer cell lines. SqC was more sensitive then AdC explained with lab observed survival curves and modeling. Short T1/2 for GTV shown quick response while short T1/2 for PTV apparently correlated with damage or toxicity of surrounding OARs for the CLLC.

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