Endobronchially Implanted Real-Time Electromagnetic Transponder Beacon-Guided, Respiratory-Gated SABR for Moving Lung Tumors: A Prospective Phase 1/2 Cohort Study

Purpose

Endobronchial electromagnetic transponder beacons (EMT) provide real-time, precise positional data of moving lung tumors. We report results of a phase 1/2, prospective, single-arm cohort study evaluating the treatment planning effects of EMT-guided SABR for moving lung tumors.

Methods and Materials

Eligible patients were adults, Eastern Cooperative Oncology Group 0 to 2, with T1-T2N0 non-small cell lung cancer or pulmonary metastasis ≤4 cm with motion amplitude ≥5 mm. Three EMTs were endobronchially implanted using navigational bronchoscopy. Four-dimensional free-breathing computed tomography simulation scans were obtained, and end-exhalation phases were used to define the gating window internal target volume. A 3-mm expansion of gating window internal target volume defined the planning target volume (PTV). EMT-guided, respiratory-gated (RG) SABR was delivered (54 Gy/3 fractions or 48 Gy/4 fractions) using volumetric modulated arc therapy. For each RG-SABR plan, a 10-phase image-guided SABR plan was generated for dosimetric comparison. PTV/organ-at-risk (OAR) metrics were tabulated and analyzed using the Wilcoxon signed-rank pair test. Treatment outcomes were evaluated using RECIST (Response Evaluation Criteria in Solid Tumours; version 1.1).

Results

Of 41 patients screened, 17 were enrolled and 2 withdrew from the study. Median age was 73 years, with 7 women. Sixty percent had T1/T2 non-small cell lung cancer and 40% had M1 disease. Median tumor diameter was 1.9 cm with 73% of targets located peripherally. Mean respiratory tumor motion was 1.25 cm (range, 0.53-4.04 cm). Thirteen tumors were treated with EMT-guided SABR and 47% of patients received 48 Gy in 4 fractions while 53% received 54 Gy in 3 fractions. RG-SABR yielded an average PTV reduction of 46.9% (P < .005). Lung V5, V10, V20, and mean lung dose had mean relative reductions of 11.3%, 20.3%, 31.1%, and 20.3%, respectively (P < .005). Dose to OARs was significantly reduced (P < .05) except for spinal cord. At 6 months, mean radiographic tumor volume reduction was 53.5% (P < .005).

Conclusions

EMT-guided RG-SABR significantly reduced PTVs of moving lung tumors compared with image-guided SABR. EMT-guided RG-SABR should be considered for tumors with large respiratory motion amplitudes or those located in close proximity to OARs.

Factors Associated with Long-Term Prostate Cancer Survival after Palliative Radiotherapy to a Bone Metastasis and Contemporary Palliative Systemic Therapy: A Retrospective, Population-Based Study

BACKGROUND

Radiation therapy (RT) is an established palliative treatment for bone metastases; however, little is known about post-radiation survival and factors which impact it. The aim of this study was to assess a population-based sample of metastatic prostate cancer patients receiving palliative radiation therapy to bone metastases and contemporary palliative systemic therapy and identify factors that impact long-term survival.

MATERIALS/METHODS

This retrospective, population-based, cohort study assessed all prostate cancer patients receiving palliative RT for bone metastases at a Canadian provincial Cancer program during a contemporary time period. Baseline patient, disease, and treatment characteristics were extracted from the provincial medical physics databases and the electronic medical record. Post-RT Survival intervals were defined as the time interval from the first fraction of palliative RT to death from any cause or date of the last known follow-up. The median survival of the cohort was used to dichotomize the cohort into short- and long-term survivors following RT. Univariable and multivariable hazard regression analyses were performed to identify variables associated with post-RT survival.

RESULTS

From 1 January 2018 until 31 December 2019, 545 palliative RT courses for bone metastases were delivered to n = 274 metastatic prostate cancer patients with a median age of 76 yrs (Interquartile range (IQR) 39-83) and a median follow-up of 10.6 months (range 0.2 to 47.9). The median survival of the cohort was 10.6 months (IQR 3.5-25 months). The ECOG performance status of the whole cohort was ≤2 in n = 200 (73%) and 3-4 in n = 67 (24.5%). The most commonly treated sites of bone metastasis were the pelvis and lower extremities n = 130 (47.4%), skull and spine n = 114 (41.6%), and chest and upper extremities n = 30 (10.9%). Most patients had CHAARTED high volume disease n = 239 (87.2%). On multivariable hazard regression analysis, an ECOG performance status of 3-4 (p = 0.02), CHAARTED high volume disease burden (p = 0.023), and non-receipt of systemic therapy (p = 0.006) were significantly associated with worse post-RT survival.

CONCLUSION

Amongst metastatic prostate cancer patients treated with palliative radiotherapy to bone metastases and modern palliative systemic therapies, ECOG performance status, CHAARTED metastatic disease burden, and type of first-line palliative systemic therapy were significantly associated with post-RT survival durations.

Abstract 4858: Effect of mTOR activity in peripheral blood mononuclear cells with metformin in high-risk prostate cancer patients receiving external beam radiotherapy and androgen deprivation therapy

Introduction: There is considerable interest in the antineoplastic properties of metformin for prostate cancer treatment, however, the underlying mechanism of action of metformin in this setting is poorly understood. It is suspected that metformin’s antineoplastic activity is related to inhibition of mTOR (mammalian target of rapamycin), which ultimately inhibits cell proliferation. In this pilot study, we assessed the mTOR activity of peripheral blood mononuclear cells (PBMCs) from high-risk Prostate cancer (PCa) patients treated with androgen deprivation therapy (ADT) and external beam radiotherapy (EBRT) plus metformin versus placebo. We hypothesized decreased mTOR expression in PBMCs from patients receiving metformin versus placebo.

Methods: Normoglycemic adult males with high-risk PCa receiving ADT & EBRT were randomized to metformin 500 mg 3 times daily or placebo. Peripheral blood samples were collected from participants

≥ 6 months after starting study drug, buffy coats were extracted, and PBMCs were isolated ≤2 hours after specimen collection using ficoll-hypaque density gradient method. The mTOR expression was assessed by phosphorylation of serine 2448 (pmTOR; S2448). Activity of mTOR was measured in both unstimulated or stimulated (using CD3/CD28 antibodies) CD4+ and CD8+ T cells.

Results: Samples from 15 patients were analyzed (11 placebo & 4 metformin). We observed lower expression of pmTOR in PBMCs in patients receiving metformin compared to placebo indicating metformin demonstrated inhibition of mTOR activity in PBMCs. A general trend of mTOR inhibition was observed in the metformin group across the cell population and conditions (unstimulated vs. stimulated T cell populations). However, the most pronounced difference was observed in unstimulated CD4+ cells, which is of interest since they represent the closest physiological state to the study participants.

Conclusion: In this pilot study, we observed mTOR inhibition in the PBMCs of PCa patients treated with metformin. Further assessment of mTOR activity amongst PCa patients receiving metformin is warranted in order to confirm these findings.

Citation Format: Febin Antony, Anuraag Shrivastav, Arbind Dubey, Nawaid Usmani, Aldrich Ong, Rashmi Koul, Harvey Quon, Gokulan Sivananthan, William Hunter, Don Yee, Lindsay Rowe, Brita Danielson, Andrew Plesniarski, Ruey-Chyi Su, Julian O. Kim. Effect of mTOR activity in peripheral blood mononuclear cells with metformin in high-risk prostate cancer patients receiving external beam radiotherapy and androgen deprivation therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4858.

Metformin for Prevention of Anthropometric and Metabolic Complications of Androgen Deprivation Therapy in Prostate Cancer Patients Receiving Radical Radiotherapy: A Phase II Randomized Controlled Trial

BACKGROUND

Patients with prostate cancer undergoing treatment with radical radiation therapy (RT) plus androgen deprivation therapy (ADT) experience a constellation of deleterious metabolic and anthropometric changes related to hypogonadism that are associated with increased morbidity and mortality. We assessed the effect of metformin versus placebo to blunt the adverse effects of ADT on body weight, waist circumference, and other metabolic parameters.

METHODS AND MATERIALS

This phase 2, multicenter, randomized controlled trial (RCT) randomized normoglycemic men with locally advanced prostate cancer receiving radical RT and ADT (18-36 months) in a 1:1 ratio to receive metformin 500 mg by mouth 3 times a day (for 30-36 months) versus identical placebo.

RESULTS

From December 2015 to October 2019, 83 men were randomized with median follow-up of 23 months. Baseline mean body mass Index (BMI) of the cohort was 30.2 (range 22.2-52.5). Change in mean weight relative to baseline was lower among men who received metformin compared with placebo at 5 months (-1.80 kg, P = .038), but was not significant with longer follow-up (1 year: +0.16 kg, P = .874). Although participants on ADT had increases in waist circumference in both study arms, metformin did not significantly reduce these changes (1 year: +2.79 cm (placebo) versus +1.46 cm (metformin), P = .336). Low-density lipoprotein (LDL) cholesterol was lower in the metformin arm (-0.32 mmol/L) compared with the placebo arm (-0.03 mmol/L) at 5 months (P = .022), but these differences were not significant with longer follow-up (1 year: -0.17 mmol/L vs -0.19 mmol/L, P = .896). There were no differences in HbA1C, triglyceride, high-density lipoprotein (HDL) cholesterol, and total cholesterol by study arm.

CONCLUSIONS

Men receiving radical RT and ADT gained weight and had increases in waist circumference over time that metformin did not significantly mitigate. Although this study did not observe any preventive effect of metformin on the anthropometric and metabolic complications of ADT, metformin continues to be studied in phase 3 RCTs in this patient population to assess its potential antineoplastic effects.

Implementation and Safety of a Single Fraction Peripheral Lung SBRT during the Global COVID-19 Pandemic, a Single Institution's Experience

Purpose/Objective(s)

In response to the COVID-19 pandemic, a single fraction peripheral lung SBRT program was established to minimize potential COVID-19 exposures. This analysis aims to review clinical and treatment characteristics and associated toxicities in appropriately selected patients for this newly implemented technique.

Materials/Methods

From May 2020 until Feb 2022, patients with peripheral lung tumors who met eligibility for 3400cGy in a single-fraction SBRT were treated at a tertiary academic cancer center. Patient, treatment, and toxicity parameters were retrospectively collected. Radiation dosimetric parameters were tabulated. Toxicities were quantified using CTCAE v5.0. Fisher's exact test was used to assess the differences in toxicities with clinical and dosimetric parameters. P-value < 0.05 was considered significant.

Results

23 patients were analyzed with a median age of 72 years (IRQ: 67-80) and 61% were females. 96% were smokers and 43% had COPD. All patients were ECOG ≤ 2. Majority of patients (96%) had early-stage primary lung cancer while 4% had pulmonary oligometastatic cancer. 39% of patients were treated on SABR-BRIDGE protocol while another 35% were medically inoperable and 26% refused surgery. A total of 23 peripheral lesions were treated with median greatest dimension of 1.7 cm (IQR: 1.4-2), ITV 4.9 cm³ (IQR: 3.6-8.4) and PTV 18.1 cm³ (IQR: 12.8-26). 87% had PTV within 1 cm form chest wall. After median follow-up of 6 months (IQR: 2-12), 52% of patients experienced grade ≤ 2 toxicities and no patients experienced ≥ grade 3. Radiation pneumonitis was the most common toxicity (35%; 5/8 with asymptomatic radiographic) followed by fatigue (30%) and chest wall pain (30%; 3/7 with grade 2). Two patients (9%) had rib fractures. Chest wall pain was significantly higher in patients with tumor diameter >1.5 cm (p = 0.02). No other significant difference was observed between clinical or dosimetric parameters and development of radiation pneumonitis or chest wall pain (p > 0.05). On the other hand, patients with ribs fractures were observed to have larger tumors (mean 3.2 vs. 1.7 cm), ITVs (mean 30 vs. 11 cm³), PTVs (mean 61 vs. 16 cm³), chest wall V30_Gy (mean 4.8 vs. 0.4 cm³), and ribs V30_Gy (mean 1.1 vs. 0.1 cm³). Only 1 patient had local failure after 12 months while another patient on SABR-BRIDGE underwent surgical resection after 6 months in which there were 20% viable tumor cells.

Conclusion

Single fraction peripheral lung SBRT is a practical and safe option with no grade ≥ 3 toxicity. Our observed toxicities are within previously reported ranges. We observed that patients with rib fractures had larger tumors and higher V30_Gy to chest wall and ribs. Careful patient selection and dosimetric efforts to limit high fall-off dose to chest wall and ribs may limit these toxicities.

Gastrointestinal and genitourinary toxicity profiles of metformin versus placebo in men with prostate cancer receiving prostate radiotherapy: interim toxicity results of a double-blinded, multicenter, phase II randomized controlled trial

Androgen deprivation therapy (ADT) used for prostate cancer (PCa) management is associated with metabolic and anthropometric toxicity. Metformin given concurrent to ADT is hypothesized to counteract these changes. This planned interim analysis reports the gastrointestinal and genitourinary toxicity profiles of PCa patients receiving ADT and prostate/pelvic radiotherapy plus metformin versus placebo as part of a phase 2 randomized controlled trial. Men with intermediate or high-risk PCa were randomized 1:1 to metformin versus placebo. Both groups were given ADT for 18–36 months with minimum 2-month neoadjuvant phase prior to radiotherapy. Acute gastrointestinal and genitourinary toxicities were quantified using CTCAE v4.0. Differences in ≥ grade 2 toxicities by treatment were assessed by chi-squared test. 83 patients were enrolled with 44 patients randomized to placebo and 39 randomized to metformin. There were no significant differences at any time point in ≥ grade 2 gastrointestinal toxicities or overall gastrointestinal toxicity. Overall ≥ grade 2 gastrointestinal toxicity was low prior to radiotherapy (7.9% (placebo) vs. 3.1% (metformin), p = 0.39) and at the end of radiotherapy (2.8% (placebo) vs 3.1% (metformin), p = 0.64). There were no differences in overall ≥ grade 2 genitourinary toxicity between treatment arms (19.0% (placebo) vs. 9.4% (metformin), p = 0.30). Metformin added to radiotherapy and ADT did not increase rates of ≥ grade 2 gastrointestinal or genitourinary toxicity and is generally safe and well-tolerated.

Bracing for impact with new 4R's in the COVID-19 pandemic - A provincial thoracic radiation oncology consensus

As COVID-19 pandemic continues to explode, cancer centers worldwide are trying to adapt and are struggling with this constantly changing scenario. Intending to ensure patient safety and deliver quality care, we sought consensus on the preferred thoracic radiation regimen in a Canadian province with 4 new R's of COVID era.

Prognostic markers of recurrence and survival in rectal cancer treated with neoadjuvant chemoradiotherapy and surgery

Aim: To identify markers of recurrence and survival in patients with locally advanced rectal cancer who received neoadjuvant chemoradiotherapy and surgery. Materials & methods: A total of 280 patients were identified in Manitoba between 2007 and 2012. Demographics and clinical data were collected. Cox regression models were used to identify outcome predictors. Results: A total of 53 patients achieved pathological complete response (pCR) and 160 patients received adjuvant chemotherapy (ACT). The median follow-up duration was 2.06 years. Recurrence and survival rates at 5 years were 33.2 and 77.0%, respectively. pCR and lymphovascular invasion predicted recurrence. pCR and ACT predicted better survival. Conclusion: pCR is a significant predictor of recurrence and survival and may be considered as an oncological end point. The patients who achieve pCR may not derive additional survival benefit from ACT.

Family physicians who have focused practices in oncology: results of a national survey

OBJECTIVE

To characterize the demographic characteristics, practice profile, and current work life of general practitioners in oncology (GPOs) for the first time.

DESIGN

National Web survey performed in March 2011.

SETTING

Canada.

PARTICIPANTS

Members of the national GPO organization. Respondents were asked to forward the survey to non-member colleagues.

MAIN OUTCOME MEASURES

Profile of work as GPOs and in other medical roles, training received, demographic characteristics, and professional satisfaction.

RESULTS

The response rate was 73.3% for members of the Canadian Association of General Practitioners in Oncology; overall, 120 surveys were completed. Respondents worked in similar proportions in small and larger communities. About 60% of them had participated in formal training programs. Most respondents worked part-time as GPOs and also worked in other medical roles, particularly palliative care, primary care practice, teaching, and hospital work. More GPOs from cities with populations of greater than 100 000 worked solely as GPOs than those from smaller communities (P = .0057). General practitioners in oncology played a variety of roles in the cancer care system, particularly in systemic therapy, palliative care, inpatient care, and teaching. As a group, more than half of respondents were involved in the care of each of the 11 common cancer types. Overall, 87.8% of respondents worked in outpatient care, 59.1% provided inpatient care, and 33.0% provided on-call services; 92.8% were satisfied with their work as GPOs.

CONCLUSION

General practitioners in oncology are involved in all cancer care settings and usually combine this work with other roles, particularly with palliative care in rural Canada. Training is inconsistent but initiatives are under way to address this. Job satisfaction is better than that of Canadian FPs in general. As generalists, FPs bring a valuable skill set to their work as GPOs in the cancer care system.

Analysis of wait times and costs during the peri-diagnostic period for non-small cell lung cancer

PURPOSE

To determine the wait times and healthcare costs around the time of non-small cell lung cancer (NSCLC) diagnosis for a large, population-based cohort of patients.

METHODS

Data on baseline demographics, diagnostic and staging tests, timelines of investigations, and frequency of physician visits and hospital admissions were obtained from a provincial cancer registry and health administrative databases for 2852 patients, who were diagnosed with NSCLC from 1996 to 2000 in Manitoba, Canada. Dates between investigations were used to determine wait times surrounding diagnosis and fee codes for physician and hospital services were used to estimate costs.

RESULTS

The median wait times from chest x-ray to chest computed tomography (CT) scan and from CT scan to definitive histological diagnosis were 8 (inter-quartile range 1-25) and 18 (inter-quartile range 3-42) days, respectively. At least 25% of patients waited more than 55 days from initial suspicion on chest x-ray to final diagnosis of NSCLC. The mean cost per case of NSCLC diagnosis was $6,978 (in Canadian dollars) where the majority of expenses was attributed to hospital admissions and repeated physician visits before a diagnosis was confirmed.

CONCLUSIONS

Despite clinical suspicion for NSCLC, a significant number of patients wait more than 8 weeks for a definitive diagnosis. Substantial costs are incurred by the Canadian universal healthcare system in the months surrounding diagnosis. Establishment of more efficient and cost-effective healthcare delivery in the peri-diagnostic time period may benefit the system as well as the patients.