Stereotactic Ablative Radiotherapy for Oligo-Progressive Cancers: Results of the Randomized Phase II STOP Trial

PURPOSE/OBJECTIVE(S)

In the metastatic setting, there is uncertain benefit to localized eradication of one or more lesions that are progressing despite systemic therapy. This randomized phase II trial examined if patients with ≤5 sites of oligoprogression benefited from the addition of stereotactic ablative radiotherapy (SABR) to standard of care (SOC) systemic therapy.

MATERIALS/METHODS

Eligibility criteria included age ≥18 years, ECOG performance status 0-2, and oligoprogressive disease, defined as 1-5 lesions actively progressing while on systemic therapy. Patients were required to have at least 3 months of disease stability/response on systemic therapy prior to oligoprogression. After stratifying by type of systemic therapy (cytotoxic vs. non-cytotoxic), patients were randomized 2:1 to SABR to all progressing lesions plus SOC (SABR arm) vs. SOC alone (SOC arm). The trial began exclusive to non-small cell lung cancer but did not meet accrual goals and was expanded in 2019 to include all non-hematologic malignancies. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), lesional control, quality of life (QOL), toxicity, and duration of current systemic agent post-SABR.

RESULTS

Between February 2017 and June 2021, 90 patients with 125 oligoprogressive metastases were enrolled across 8 Canadian institutions, with 59 patients randomized to SABR and 31 to SOC. Median age was 67 years (IQR: 61-73 years) and 39 (43%) were female. The most common primary sites were lung (44% of patients), genitourinary (23%) and breast (13%), with the most common oligo-progressive locations being lung (43%), bone (19%), lymph nodes (14%), and liver (13%). In the SABR arm, the most common fractionations were 35 Gy/5 (38% of lesions) and 50 Gy/5 (18%). Protocol adherence in the SOC arm was suboptimal: 3 patients (10%) withdrew immediately after randomization, and 7 additional patients (23%) received high-dose or ablative therapies. Median follow-up was 31 months. There was no difference in PFS between arms (median PFS 8.4 months in the SABR arm vs. 4.3 months in the SOC arm; however, the curves cross and 2-year PFS was 9% vs. 24% respectively, p = 0.91). Median OS was 31.2 months vs. 27.4 months, respectively (p = 0.22). Lesional control with SABR was 71% vs. 39% with SOC (p = 0.002). Median duration of post-randomization first-line systemic therapy was 10.3 months vs. 7.6 months, respectively (p = 0.71). Treatment was well-tolerated with 2 (3.4%) grade 3 treatment-related toxicities in the SABR arm and no grade 4/5 related events in either arm. QOL did not differ between arms.

CONCLUSION

Despite being a well-tolerated treatment providing superior lesional control, SABR for oligoprogression did not improve PFS or OS. Results may have been impacted by withdrawals and desire for ablative treatments on the SOC arm, and this lack of equipoise may make accrual to phase III trials difficult, although larger studies in select sub-populations are desired. (NCT02756793).

Skin Toxicity in Early Breast Cancer Patients Treated with Field-In-Field Breast Intensity-Modulated Radiotherapy versus Helical Inverse Breast Intensity-Modulated Radiotherapy: Results of a Phase III Randomised Controlled Trial

AIMS

Skin toxicity is a common adverse effect of breast radiotherapy. We investigated whether inverse-planned intensity-modulated radiotherapy (IMRT) would reduce the incidence of skin toxicity compared with forward field-in-field breast IMRT (FiF-IMRT) in early stage breast cancer.

MATERIALS AND METHODS

This phase III randomised controlled trial compared whole-breast irradiation with either FiF-IMRT or helical tomotherapy IMRT (HT-IMRT), with skin toxicity as the primary end point. Patients received 50 Gy in 25 fractions and were assessed to compare skin toxicity between treatment arms.

RESULTS

In total, 177 patients were available for assessment and the median follow-up was 73.1 months. Inverse IMRT achieved more homogeneous coverage than FiF-IMRT; erythema and moist desquamation were higher with FiF-IMRT compared with HT-IMRT (61% versus 34%; P < 0.001; 33% versus 11%; P < 0.001, respectively). Multivariate analysis showed large breast volume, FiF-IMRT and chemotherapy were independent factors associated with worse acute toxicity. There was no difference between treatment arms in the incidence of late toxicities. The 5-year recurrence-free survival was 96.3% for both FiF-IMRT and HT-IMRT and the 5-year overall survival was 96.3% for FiF-IMRT and 97.4% for HT-IMRT.

CONCLUSIONS

Our study showed significant reduction in acute skin toxicity using HT-IMRT compared with FiF-IMRT, without significant reduction in late skin toxicities. On the basis of these findings, inverse-planned IMRT could be used in routine practice for whole-breast irradiation with careful plan optimisation to achieve the required dose constraints for organs at risk.

Management of small-cell lung cancer with radiotherapy-a pan-Canadian survey of radiation oncologists

BACKGROUND

The management of small-cell lung cancer (sclc) with radiotherapy (rt) varies, with many treatment regimens having been described in the literature. We created a survey to assess patterns of practice and clinical decision-making in the management of sclc by Canadian radiation oncologists (ros).

METHODS

A 35-item survey was sent by e-mail to Canadian ros. The questions investigated the role of rt, the dose and timing of rt, target delineation, and use of prophylactic cranial irradiation (pci) in limited-stage (ls) and extensive-stage (es) sclc.

RESULTS

Responses were received from 52 eligible ros. For ls-sclc, staging (98%) and simulation or dosimetric (96%) computed tomography imaging were key determinants of rt suitability. The most common dose and fractionation schedule was 40-45 Gy in 15 once-daily fractions (40%), with elective nodal irradiation performed by 31% of ros. Preferred management of clinical T1/2aN0 sclc favoured primary chemoradiotherapy (64%). For es-sclc, consolidative thoracic rt was frequently offered (88%), with a preferred dose and fractionation schedule of 30 Gy in 10 once-daily fractions (70%). Extrathoracic consolidative rt would not be offered by 23 ros (44%). Prophylactic cranial irradiation was generally offered in ls-sclc (100%) and es-sclc (98%) after response to initial treatment. Performance status, baseline cognition, and pre-pci brain imaging were important patient factors assessed before an offer of pci.

CONCLUSIONS

Canadian ros show practice variation in sclc management. Future clinical trials and national treatment guidelines might reduce variability in the treatment of early-stage disease, optimization of dose and targeting in ls-sclc, and definition of suitability for pci or consolidative rt.

SU-E-J-151: Evaluation of a Real Time Tumour Autocontouring Algorithm Using In-Vivo Lung MR Images with Various Contrast to Noise Ratios

PURPOSE

To quantitatively evaluate a lung tumour autocontouring algorithm using in-vivo lung cancer patient MR images with varying contrast to noise ratios (CNR) simulating images acquired at various MR field strengths.

METHODS

A non small cell lung cancer patient with posterior lung tumour is imaged (sagittal plane) in a 3T MRI using a dynamic bSSFP sequence (FOV: 40×40cm² , voxel size: 3.1×3.1×20mm³ , TE = 1.1ms. TR = 2.2ms, 275ms per image) under free breathing for approximately 3 minutes (650 images). Gaussian random noise is added to the 3T images to approximately simulate the equivalent CNR in images acquired at 1.5T, 1.0T, 0.5T, 0.3T and 0.2T. The moving tumour in all 3T images is contoured by a physician for reference. The first 20 of these manual contours are used for the parameters optimization of auto-contouring algorithm. The automatic contours from the remaining images are quantitatively compared with the physician's contours using the centroid's displacement and the Dice's coefficient (DC).

RESULTS

The oncologist's contours of the 3T images show a maximum S-I motion of 26mm. Compared to the oncologist's contours, automatic contours have an average centroid displacement of 1.37mm, and an average DC of 0.881. The autocontouring algorithm's performance with images in the range of 1.5T to 0.5T equivalent CNRs is similar to that of the 3T data. However, for the lowest CNR datasets (0.2, 0.3T) an increase in centroid displacement and decrease in DC is observed, with mean displacements of 1.56mm, 1.71mm and DCs of 0.870, 0.836 for the 0.3T and 0.2T dataset, respectivelyConclusions: With in-vivo MR images, the autocontouring algorithm generated lung tumour contours similar to ones drawn by a physician (DC 〉 0.83). In this patient, additional CNR from 〉0.5T MRIs does not provide statistically significant improvement in the accuracy of our autocontouring software. E.Yip is supported by the Canadian Institutes of Health Research as well as Alberta Innovates - Health Solutions.

The Canadian Association of Radiation Oncology scope of practice guidelines for lung, liver and spine stereotactic body radiotherapy

AIMS

The Canadian Association of Radiation Oncology-Stereotactic Body Radiotherapy (CARO-SBRT) Task Force was established in 2010. The aim was to define the scope of practice guidelines for the profession to ensure safe practice specific for the most common sites of lung, liver and spine SBRT.

MATERIALS AND METHODS

A group of Canadian SBRT experts were charged by our national radiation oncology organisation (CARO) to define the basic principles and technologies for SBRT practice, to propose the minimum technological requirements for safe practice with a focus on simulation and image guidance and to outline procedural considerations for radiation oncology departments to consider when establishing an SBRT programme.

RESULTS

We recognised that SBRT should be considered as a specific programme within a radiation department, and we provide a definition of SBRT according to a Canadian consensus. We outlined the basic requirements for safe simulation as they pertain to spine, lung and liver tumours, and the fundamentals of image guidance. The roles of the radiation oncologist, medical physicist and dosimetrist have been detailed such that we strongly recommend the development of SBRT-specific teams. Quality assurance is a key programmatic aspect for safe SBRT practice, and we outline the basic principles of appropriate quality assurance specific to SBRT.

CONCLUSION

This CARO scope of practice guideline for SBRT is specific to liver, lung and spine tumours. The task force recommendations are designed to assist departments in establishing safe and robust SBRT programmes.

Prognostic significance of HER-2/neu over-expression on the incidence of brain metastasis in newly diagnosed breast cancer

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Background: As systemic therapy improves, brain metastases (BM) from breast cancer are becoming increasingly evident. An increased risk of BM in HER-2/neu over-expressing metastatic breast cancer patients has been suggested. However, the relationship between HER-2/neu over-expression and the risk of BM in newly diagnosed breast cancer patients is unknown. Methods: To determine incidence of BM in HER-2/neu over-expressing breast cancer patients, a cohort of patients between 01/1998 and 12/2003 with uniform HER-2/neu testing were identified from a cancer registry. A total of 460 patients with HER-2/neu over-expression and 500 patients with HER-2/neu negative disease were reviewed. Patients were excluded if there was breast cancer diagnosed before 01/1998 or others cancer. A total of 301 HER-2/neu over-expressing and 363 HER-2/neu negative patients were included for this analysis. The association between histological features and the occurrence of BM were evaluated with univariate and multivariate analyses. Results: BM were identified in 8% (24 patients) of HER-2/neu over-expressing breast cancer patients compared to only 1.7% (6 patients) in the HER-2/neu negative patients (hazard ratio 5.15 [2.079–12.78], p=0.0001). In patients with recurrent disease, the proportion of BM for HER-2/neu over-expressing patients was 24% compared to 10% in HER-2/neu negative patients. HER-2/neu over-expression, tumor size >2cm, ≥ 4 nodes positive and grade 2/3 were predictors of BM in univariate analysis. In multivariate analysis, HER-2/neu over-expression and tumor size>2cm were an independent prognostic factors for the development of BM, while hormone receptors expressions was protective (p=0.02). Conclusions: Our population based study show that newly diagnosed HER-2/neu over-expressing breast cancer patients are at significantly increased risk for BM. As most BM occur in HER-2/neu over-expressing patients with systemic metastatic disease, these findings could prompt consideration of brain prophylaxis strategies and/or serial radiologic screening to detect asymptomatic BM.

No significant financial relationships to disclose.

Anti-MUC-1 immunoliposomal doxorubicin in the treatment of murine models of metastatic breast cancer

The fate of breast cancer patients is dependent upon elimination or control of metastases. We studied the effect of antibody-targeted liposomes containing entrapped doxorubicin (DXR) on development of tumours in two models of breast cancer, pseudometastatic and metastatic, in mice. The former used the mouse mammary carcinoma cell line GZHI, which expresses the human MUC-1 gene (L. Ding, E.N. Lalani, M. Reddish, R. Koganty, T. Wong, J. Samuel, M.B. Yacyshyn, A. Meikle, P.Y.S. Fung, J. Taylor-Papadimitriou, B.M. Longenecker, Cancer Immunol. Immunother. 36 (1993) 9--17). GZHI cells seed into the lungs of Balb/c mice following intravenous injection. The latter used the 4T1-MUC1 cell line, a MUC-1 transfectant of the mouse mammary carcinoma cell line 4T1, which metastasizes from a primary mammary fatpad (mfp) implant to the lungs (C.J. Aslakson, F.R. Miller, Cancer Res. 52 (1992) 1399--1405). B27.29, a monoclonal antibody against the MUC-1 antigen, was used to target sterically stabilized immunoliposomes (SIL[B27.29]) to tumour cells. In vitro, SIL[B27.29] showed high specific binding to both GZHI and 4T1-MUC1 cells. The IC(50) of DXR-loaded SIL[B27.29] was similar to that of free drug for GZHI cells. In the pseudometastatic model, mice treated with a single injection of 6 mg DXR/kg in DXR-SIL[B27.29] at 24 h after cell implantation had longer survival times than those injected with non-targeted liposomal drug. In the metastatic model, severe combined immune deficiency mice given weekly injectionsx3 of 2.5 mg DXR/kg encapsulated in either targeted or non-targeted liposomes were almost equally effective in slowing growth of the primary tumour and reducing development of lung tumours. Surgical removal of the primary tumour from mfp, followed by various chemotherapy regimens, was attempted, but removal of the primary tumour was generally incomplete; tumour regrowth occurred and metastases developed in the lungs in all treatment groups. DXR-SL reduced the occurrence of regrowth of the primary tumour, whereas neither targeted liposomal drug or free drug prevented regrowth. We conclude that monoclonal antibody-targeted liposomal DXR is effective in treating early lesions in both the pseudometastatic and metastatic models, but limitations to the access of the targeted liposomes to tumour cells in the primary tumour compromised their therapeutic efficacy in treating the more advanced lesions.