IMRT reduces acute hematologic and GI toxicity compared with standard treatment, with promising therapeutic outcomes. Positron emission tomography IG-IMRT reduces the incidence of acute neutropenia.
Purpose
To demonstrate an efficient method for training and validation of a knowledge-based planning (KBP) system as a radiotherapy clinical trial plan quality control (QC) system.
Methods
We analyzed 86 stage IB-IVA cervical cancer patients treated with intensity modulated radiotherapy (IMRT) at two institutions according to XXXXX multi-institutional protocol standards. The protocol utilized a planning target volume (PTV) and two primary organs-at-risk (OARs): pelvic bone marrow (PBM) and bowel. Secondary OARs were rectum and bladder. Initial UNFILTERED dose-volume histogram (DVH) estimation models were trained using all 86 plans. REFINED training sets and DVH-estimation models were constructed by identifying 30/86 plans emphasizing PBM-sparing (comparing protocol-specified V10 and V20 with UNFILTERED predictions), and another 30/86 plans emphasizing bowel sparing (comparing V40 and V45, 9 in common with PBM set). To obtain deliverable KBP plans, REFINED models must inform patient-specific optimization objectives/priorities (an auto-planning “routine”). Four candidate routines emphasizing different tradeoffs were composed and a script was developed to automatically re-plan multiple patients with each routine. After selection of the routine best meeting protocol objectives in the 51-patient training sample (KBPFINAL), protocol-specific DVH metrics and normal tissue complication probability (NTCP) were compared for original vs. KBPFINAL plans across the 35-patient validation set. Paired t-tests tested differences between planning sets.
Results
KBPFINAL plans outperformed manual planning across the validation set in all protocol-specific DVH cutpoints. The mean NTCP for GI toxicity was lower for KBPFINAL vs. validation-set plans (48.7% vs. 53.8%, p<.001). Similarly, the estimated mean white blood cell count (WBC) nadir was higher (2.77 vs 2.49, p<.001) with KBPFINAL plans, indicating lowered probability of hematologic toxicity.
Conclusions
This work demonstrates that a KBP system can be efficiently trained and refined for use in radiotherapy clinical trials with minimal effort. This patient-specific plan QC resulted in improvements on protocol-specific dosimetric endpoints.
Our study suggests that perioperative HDR BT is a promising method for achieving high biological doses with good LC in the postoperative radiotherapy of STS and that combination of BT and EBRT provides better tumor control than BT alone.
Sufficient dose coverage of target volumes was not achieved for all patients. Reducing of safety margin is not acceptable. Initial rectal and bladder volumes cannot be considered representative for subsequent treatment.
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