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Background A recent randomized phase II trial evaluated stereotactic ablative radiotherapy (SABR) in a group of patients with a small burden of oligometastatic disease (mostly with 1–3 metastatic lesions), and found that SABR was associated with a significant improvement in progression-free survival and a trend to an overall survival benefit, supporting progression to phase III randomized trials. Methods Two hundred and ninety-seven patients will be randomized in a 1:2 ratio between the control arm (consisting of standard of care [SOC] palliative-intent treatments), and the SABR arm (consisting of SOC treatment + SABR to all sites of known disease). Randomization will be stratified by two factors: histology (prostate, breast, or renal vs. all others), and disease-free interval (defined as time from diagnosis of primary tumor until first detection of the metastases being treated on this trial; divided as ≤2 vs. > 2 years). The primary endpoint is overall survival, and secondary endpoints include progression-free survival, cost effectiveness, time to development of new metastatic lesions, quality of life (QoL), and toxicity. Translational endpoints include assessment of circulating tumor cells, cell-free DNA, and tumor tissue as prognostic and predictive markers, including assessment of immunological predictors of response and long-term survival. Discussion This study will provide an assessment of the impact of SABR on survival, QoL, and cost effectiveness to determine if long-term survival can be achieved for selected patients with 1–3 oligometastatic lesions. Trial registration Clinicaltrials.gov identifier: NCT03862911 . Date of registration: March 5, 2019,

Background Breast cancer is the leading cause of global cancer incidence. In early-stage disease, standard treatment with breast-conserving surgery followed by whole breast irradiation (WBI) is associated with excellent outcomes. Multiple studies with extensive follow-up periods have demonstrated the comparative efficacy and toxicity outcomes of partial breast irradiation (PBI) in contrast to WBI. Various dose fractionation schedules for PBI have been recommended in clinical practice guidelines. In British Columbia (BC), a dose of 26 Gy in 5 fractions has been adopted. Early studies on single-fraction (SF) radiation for PBI have investigated its safety and effect on cosmetic outcomes, with promising initial results. In the context of the ongoing health care crisis, single-fraction PBI has the potential to reduce wait times and improve access to radiation. This study will therefore investigate a single-fraction PBI dose of 13 Gy. Methods This is a phase II randomized controlled trial, with a primary objective of testing the feasibility of randomizing participants to 1 vs. 5 fractions of PBI for early stage, node negative, breast cancer. The primary endpoint is the ability to accrue 60 participants at 4 of the 6 BC Cancer centres over a 2- year period and to randomize them to 1 vs. 5 fractions of radiotherapy for PBI. Its secondary endpoints are time from CT simulation to partial breast radiotherapy, local control rates, quality of life as measured by Prospective Outcomes and Support Initiative (POSI)-Breast, rates of provider-rated toxicities as measured by Common Terminology Criteria for Adverse Events (CTCAE), rates of participant-reported toxicities as measured by participant reported outcome version of CTCAE (PRO-CTCAE), overall survival, and progression-free survival. Discussion One of the trial’s objectives is testing the feasibility of randomizing participants to single vs. multiple fractions for PBI. If successful, it will lead to a phase III non-inferiority trial with the potential to inform breast cancer treatment guidelines. Ultimately, if found to be non-inferior, a single-fraction PBI can reduce wait times, facilitate access to radiation, and improve patient convenience, particularly for those in rural and remote communities who must travel long distances to receive high-quality cancer care. Trial registration Clinicaltrials.gov identifier: NCT06885671. Date of Registration: 14 March 2025.

Background Oligometastases refer to a state of disease where cancer has spread beyond the primary site, but is not yet widely metastatic, often defined as 1–3 or 1–5 metastases in number. Stereotactic ablative radiotherapy (SABR) is an emerging radiotherapy technique to treat oligometastases that require further prospective population-based toxicity estimates. Methods This is a non-randomized phase II trial where all participants will receive experimental SABR treatment to all sites of newly diagnosed or progressing oligometastatic disease. We will accrue 200 patients to assess toxicity associated with this experimental treatment. The study was powered to give a 95% confidence on the risk of late grade 4 toxicity, anticipating a < 5% rate of grade 4 toxicity. Discussion SABR treatment of oligometastases is occurring off-trial at a high rate, without sufficient evidence of its efficacy or toxicity. This trial will provide necessary toxicity data in a population-based cohort, using standardized doses and organ at risk constraints, while we await data on efficacy from randomized phase III trials. Trial Registration Registered through clinicaltrials.gov NCT02933242 on October 14, 2016 prospectively before patient accrual.

Background Bone metastases in the lower spine and pelvis are effectively palliated with radiotherapy (RT), though this can come with side effects such as radiation induced nausea and vomiting (RINV). We hypothesize that high rates of RINV occur in part because of the widespread use of inexpensive simple unplanned palliative radiotherapy (SUPR), over more complex and resource intensive 3D conformal RT, such as volumetric modulated arc therapy (VMAT). Methods This is a randomized, multi-centre phase III trial of SUPR versus VMAT. We will accrue 250 patients to assess the difference in patient-reported RINV. This study is powered to detect a difference in quality of life between patients treated with VMAT vs. SUPR. Discussion This trial will determine if VMAT reduces early toxicity compared to SUPR and may provide justification for this more resource-intensive and costly form of RT. Trial registration Clinicaltrials.gov identifier: NCT03694015 . Date of registration: October 3, 2018.

Background The purpose of this study is to evaluate the clinical impact of using deformable registration in tumor volume definition between separately acquired PET/CT and planning CT images. Methods Ten lung and 10 head and neck cancer patients were retrospectively selected. PET/CT images were registered with planning CT scans using commercially available software. Radiation oncologists defined two sets of gross tumor volumes based on either rigidly or deformably registered PET/CT images, and properties of these volumes were then compared. Results The average displacement between rigid and deformable gross tumor volumes was 1.8 mm (0.7 mm) with a standard deviation of 1.0 mm (0.6 mm) for the head and neck (lung) cancer subjects. The Dice similarity coefficients ranged from 0.76-0.92 and 0.76-0.97 for the head and neck and lung subjects, respectively, indicating conformity. All gross tumor volumes received at least 95% of the prescribed dose to 99% of their volume. Differences in the mean radiation dose delivered to the gross tumor volumes were at most 2%. Differences in the fraction of the tumor volumes receiving 100% of the radiation dose were at most 5%. Conclusions The study revealed limitations in the commercial software used to perform deformable registration. Unless significant anatomical differences between PET/CT and planning CT images are present, deformable registration was shown to be of marginal value when delineating gross tumor volumes.

To determine which web-based model best identifies women at low risk of further axillary disease after a positive sentinel lymph node (SLN+) biopsy. 673 women with T1-2cN0M0 SNB+ breast cancer who underwent completion axillary dissection (AxD) were identified. A subgroup not eligible to avoid AxD as part of the Z0011 study was defined (Z0011 exclusion group). Predicted risk of further axillary disease was generated using seven web-based models. “Low risk” was defined as a ≤10% risk of further axillary disease. False negative (“low risk” prediction but AxD+) rates (FNRs), area under the receiver operating characteristic curve (AUC), and Brier score were determined for each model. 6 of 7 models identified “low risk” patients but FNRs ranged from 14 to 30%. The Stanford and Memorial Sloan-Kettering (MSKCC) models had the best FNRs. FNRs were lower with SLN micrometastasis (7–15%) and higher in the Z0011 exclusion group (21–41%). All models under-predicted further nodal disease in low risk patients and over-predicted in higher-risk patients. The Stanford and MSKCC models were able to identify women with SLN micrometastasis with a ≤10% FNR. Models were not able to accurately identify low risk women from a cohort that would have been excluded from Z0011.

We report on a 56-year-old Caucasian female, diagnosed with locally advanced, hormone-receptor-positive, and human epidermal growth factor receptor 2 (HER2)-positive cancer of the left breast. The patient received neoadjuvant chemotherapy with adriamycin/cyclophosphamide (AC) followed by docetaxel/trastuzumab. A partial clinical and radiographical response was documented after four cycles of AC. Approximately one week after the first cycle of docetaxel and trastuzumab, the patient presented with diffuse edema, erythema, and induration involving the entire left breast. The differential diagnoses included infection, inflammatory response/reaction to docetaxel, or cancer progression. After a multidisciplinary review, the decision was made to stop the docetaxel and deliver neoadjuvant radiation treatment concurrent with trastuzumab. Approximately four weeks after radiation therapy completion, the patient underwent a left total mastectomy and axillary dissection, with pathologic complete response (pCR) in the breast and axillary nodal disease. After surgery, systemic therapy was resumed with paclitaxel and trastuzumab, with a plan to start adjuvant endocrine therapy after completion of chemotherapy. We will discuss clinical considerations in the management of the unexpected findings of acute inflammatory response in the breast and nodal regions during neoadjuvant chemotherapy. Associations between intrinsic breast cancer subtype and pCR in locally advanced breast cancer will also be reviewed.

Background This paper compares the calculated dose to target and normal tissues when using pencil beam (PBC), superposition/convolution (AAA) and Monte Carlo (MC) algorithms for whole breast (WBI) and accelerated partial breast irradiation (APBI) treatment plans. Methods Plans for 10 patients who met all dosimetry constraints on a prospective APBI protocol when using PBC calculations were recomputed with AAA and MC, keeping the monitor units and beam angles fixed. Similar calculations were performed for WBI plans on the same patients. Doses to target and normal tissue volumes were tested for significance using the paired Student's t-test. Results For WBI plans the average dose to target volumes when using PBC calculations was not significantly different than AAA calculations, the average PBC dose to the ipsilateral breast was 10.5% higher than the AAA calculations and the average MC dose to the ipsilateral breast was 11.8% lower than the PBC calculations. For ABPI plans there were no differences in dose to the planning target volume, ipsilateral breast, heart, ipsilateral lung, or contra-lateral lung. Although not significant, the maximum PBC dose to the contra-lateral breast was 1.9% higher than AAA and the PBC dose to the clinical target volume was 2.1% higher than AAA. When WBI technique is switched to APBI, there was significant reduction in dose to the ipsilateral breast when using PBC, a significant reduction in dose to the ipsilateral lung when using AAA, and a significant reduction in dose to the ipsilateral breast and lung and contra-lateral lung when using MC. Conclusions There is very good agreement between PBC, AAA and MC for all target and most normal tissues when treating with APBI and WBI and most of the differences in doses to target and normal tissues are not clinically significant. However, a commonly used dosimetry constraint, as recommended by the ASTRO consensus document for APBI, that no point in the contra-lateral breast volume should receive >3% of the prescribed dose needs to be relaxed to >5%.