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Purpose This provides a benchmark of dosimetric benefit and clinical cost of cone‐beam CT‐based online adaptive radiotherapy (ART) technology for cervical and rectal cancer patients. Methods An emulator of a CBCT‐based online ART system was used to simulate more than 300 treatments for 13 cervical and 15 rectal cancer patients. CBCT images were used to generate adaptive replans. To measure clinical resource cost, the six phases of the workflow were timed. To evaluate the dosimetric benefit, changes in dosimetric values were assessed. These included minimum dose (Dmin) and volume receiving 95% of prescription (V95%) for the planning target volume (PTV) and the clinical target volume (CTV), and maximum 2 cc's (D2cc) of the bladder, bowel, rectum, and sigmoid colon. Results The average duration of the workflow was 24.4 and 9.2 min for cervical and rectal cancer patients, respectively. A large proportion of time was dedicated to editing target contours (13.1 and 2.7 min, respectively). For cervical cancer patients, the replan changed the Dmin to the PTVs and CTVs for each fraction 0.25 and 0.25 Gy, respectively. The replan changed the V95% by 9.2 and 7.9%. The D2cc to the bladder, bowel, rectum, and sigmoid colon for each fraction changed −0.02, −0.08, −0.07, and −0.04 Gy, respectively. For rectal cancer patients, the replan changed the Dmin to the PTVs and CTVs for each fraction of 0.20 and 0.24 Gy, respectively. The replan changed the V95% by 4.1 and 1.5%. The D2cc to the bladder and bowel for each fraction changed 0.02 and −0.02 Gy, respectively. Conclusions Dosimetric benefits can be achieved with CBCT‐based online ART that is amenable to conventional appointment slots. The clinical significance of these benefits remains to be determined. Managing contours was the primary factor affecting the total duration and is imperative for safe and effective adaptive radiotherapy.

TPS5624 Background: Early stage invasive squamous cell carcinoma of the vulva is treated by radical excision of the primary tumor combined with a sentinel node (SN) procedure for the groins. GROINSS-VI and GOG-173 demonstrated that if there is no metastasis to the SN, then standard of care is observation. GROINSS-VII/GOG-270 demonstrated that micrometastatic disease ( 2mm) required IFL in order to have an acceptably low groin recurrence rate. However, IFL is associated with significant morbidity such as lymphedema, wound healing issues, and recurrent infections. It is hypothesized that for those with macrometastasis ( > 2 mm) in the SN, the efficacy of treatment can be increased by giving a higher dose of radiotherapy along with chemosensitization. Methods: This is an international multicenter single-arm phase II prospective clinical trial. The primary objective is to investigate the safety of replacing IFL by chemoradiation in early-stage vulvar cancer patients with a macrometastasis ( > 2mm) and/or extracapsular extension in the SN. The primary endpoint is the groin recurrence rate in the first two years after primary treatment. Secondary endpoints are short and long-term morbidity associated with the SN procedure and chemoradiation and quality of life as measured by EORTC-QLQc30. Patients with invasive ( > 1mm) squamous cell carcinoma of the vulva, stage T1, tumor size < 4 cm diameter and no suspicious lymph nodes by imaging of the groins will proceed with SN detection. Institutions enrolling patients must demonstrate prior surgical experience with SN detection with the submission of at least 10 successfully completed cases in vulvar cancer. Patients with SN metastases > 2mm and/or with extracapsular extension or those with > 1 SN with micrometastases will be eligible for this study. Treatment will consist of chemoradiation with a dose of 56 Gy to the groin combined with weekly cisplatin 40 mg/m2 IV on days 1, 8, 15, 21 and 29 of radiotherapy. One hundred and fifty-seven patients in Europe, United States and Canada will be enrolled. The study includes continuous monitoring of groin recurrences with stopping rules. Results of this trial may be practice changing and eliminate the need for IFL in all women with clinically early stage vulvar cancer. The study is currently open for enrollment. Clinical trial information: NCT05076942.

INTRODUCTION: Brain metastasis velocity (BMV) is a prognostic metric that describes the recurrence rate of new brain metastases after initial treatment with radiosurgery (SRS). We have previously risk stratified patients into high, intermediate, and low-risk BMV groups, which correlates with overall survival (OS). We sought to externally validate BMV in a multi-institutional setting. METHODS: Patients from nine academic centers were treated with upfront SRS; the validation cohort consisted of data from eight institutions not previously used to define BMV. Patients were classified by BMV into low (< 4 BMV), intermediate (4–13 BMV), and high-risk groups (>13 BMV). Time-to-event outcomes were estimated using the Kaplan-Meier method. Cox proportional hazards methods were used to estimate the effect of BMV and salvage modality on OS. RESULTS: Of 2829 patients, 2092 patients were included in the validation dataset. Of these, 921 (44.0%) experienced distant brain failure (DBF). Median OS from initial SRS was 11.2 mo. Median OS for BMV < 4, BMV 4–13, and BMV > 13 were 12.5 mo, 7.0 mo, and 4.6 mo (p < 0.0001). Compared to initial salvage with WBRT, salvage SRS was associated with improved OS following DBF for BMV < 4 (p = 0.05), BMV 4–13 (p = 0.002) and BMV > 13 (p = 0.0001). CONCLUSIONS: This multi-institutional dataset validates BMV as a predictor of OS following initial SRS. BMV is being utilized in upcoming multi-institutional randomized controlled trials as a stratification variable for salvage whole brain radiation vs salvage SRS after DBF.

Nutrition is important for patients with esophageal cancer because dysphagia can be exacerbated by chemoradiotherapy. Some centers suggest routine enteral tube placement (TF) to facilitate nutrition. This investigation was to evaluate the use of TF access for patients undergoing multimodality therapy for esophageal carcinoma. This retrospective study analyzed 113 patients who underwent esophagectomy and 97 patients who underwent definition chemoradiotherapy for esophageal cancer between 2001 and 2013. Throughout this time period, a strategy for selective tube placement was used. Nutrition was assessed through absolute lymphocyte counts, protein, and albumin levels. A total of 28 (30%) patients during preoperative chemoradiotherapy and 31 (32%) of those undergoing definitive chemoradiation received TFs. There were 16 Dobhoff tubes, 28 gastrostomy tubes, and 15 jejunostomies. Tubes were maintained an average of 3.9 months with 20 (34%) of these patients reporting tube-related complications. At the time of surgery, there was no statistical difference in any of the nutritional assessments between those patients who received TF and those who did not. Both groups experienced similar total postoperative complication rates (64% vs 65%) and similar median length of hospital stay (12 to 13 days). Chemoradiotherapy resulted in decreased nutritional parameters; however, there was no difference in the degree of reduction between those who underwent TF and those who did not. The data show that routine placement of enteral access is not necessary for esophageal carcinoma. In fact, the risks of placing enteral access may outweigh the benefits. Administration of TF should be restricted to select patients during chemoradiotherapy or before esophagectomy.