Knowledge Based Planning for Lung SBRT: Model Transferability between Treatment Systems and Calculation Algorithms

PURPOSE/OBJECTIVE(S)

Knowledge based planning (KBP) is known to be effective and clinically feasible in achieving high quality treatment plans with less variability between planners and reduced planning time. A KBP model is highly dependent on characteristics of the training data. Our institution developed and validated a lung SBRT KBP model from plans treated with a C-arm linear accelerator (Linac). This study aims to evaluate the quality of lung SBRT plans with a KBP model when this model is used for an O-ring Linac with different MLC design, beam quality, and calculation algorithm.

MATERIALS/METHODS

Two academic hospitals in the same healthcare network were included in this study. One hospital trained a KBP model for five-fraction lung SBRT using 43 plans calculated using the Eclipse AcurosXB v15.6 algorithm for a C-arm Linac. The model was developed to prioritize dose gradient outside the PTV while satisfying institutional critical organ limits and validated using an additional set of 12 plans. A cohort of 10 patients (11 plans) previously treated with lung SBRT using the O-ring Linac at the second hospital was selected. These plans were calculated using the Eclipse AAA v15.6 algorithm with prescription doses of 30-50 Gy in five fractions. Each plan was re-optimized using the KBP model, without manual adjustment of the optimization objectives, using the same beam geometry as in the clinical plans. KBP plans were normalized to achieve the same PTV coverage as the clinical plans. Clinical and KBP plans were evaluated for ITV D98%, PTV conformity index (CI), R50 and maximum dose at 2 cm from the PTV (D2cm).

RESULTS

All clinical and KBP plans met critical organ dose constraints. The range of CI was 1-1.13 vs. 0.96-1.05 for clinical plans and KBP plans, respectively. R50 and D2cm were lower with KBP plans (p = 0.007 and p = 0.05, respectively). ITV D98% range was 105-120% vs. 117-122% of the PTV prescription dose for clinical plans and KBP plans, respectively, and higher with KBP plans (p<0.001). For plans where the PTV overlaps the chest wall (n = 7), the maximum chest wall doses (D0.03cc) from KBP plans were higher than the clinical plans (p = 0.16), with an absolute chest wall D0.03cc difference of 9 Gy (54 Gy vs 63 Gy). The KBP model includes an ITV SIB of 120% of the PTV prescription, whereas the clinical plans reduced the ITV SIB when the PTV overlapped the chest wall, highlighting a difference in clinical practice between the two hospitals in this study.

CONCLUSION

This study supports that a lung SBRT KBP model trained using plans for one Linac system and the AcurosXB algorithm can be used to generate clinically acceptable plans without manual planner intervention for a different Linac system and the AAA calculation algorithm, indicating the potential of a KBP model use for centralized planning process across different Linac systems and calculation algorithms.

Inhibition of tyrosine kinase Fgr prevents radiation-induced pulmonary fibrosis (RIPF)

Cellular senescence is involved in the development of pulmonary fibrosis as well as in lung tissue repair and regeneration. Therefore, a strategy of removal of senescent cells by senolytic drugs may not produce the desired therapeutic result. Previously we reported that tyrosine kinase Fgr is upregulated in ionizing irradiation-induced senescent cells. Inhibition of Fgr reduces the production of profibrotic proteins by radiation-induced senescent cells in vitro; however, a mechanistic relationship between senescent cells and radiation-induced pulmonary fibrosis (RIPF) has not been established. We now report that senescent cells from the lungs of mice with RIPF, release profibrotic proteins for target cells and secrete chemotactic proteins for marrow cells. The Fgr inhibitor TL02-59, reduces this release of profibrotic chemokines from the lungs of RIPF mice, without reducing numbers of senescent cells. In vitro studies demonstrated that TL02-59 abrogates the upregulation of profibrotic genes in target cells in transwell cultures. Also, protein arrays using lung fibroblasts demonstrated that TL02-59 inhibits the production of chemokines involved in the migration of macrophages to the lung. In thoracic-irradiated mice, TL02-59 prevents RIPF, significantly reduces levels of expression of fibrotic gene products, and significantly reduces the recruitment of CD11b+ macrophages to the lungs. Bronchoalveolar lavage (BAL) cells from RIPF mice show increased Fgr and other senescent cell markers including p16. In human idiopathic pulmonary fibrosis (IPF) and in RIPF, Fgr, and other senescent cell biomarkers are increased. In both mouse and human RIPF, there is an accumulation of Fgr-positive proinflammatory CD11b+ macrophages in the lungs. Thus, elevated levels of Fgr in lung senescent cells upregulate profibrotic gene products, and chemokines that might be responsible for macrophage infiltration into lungs. The detection of Fgr in senescent cells that are obtained from BAL during the development of RIPF may help predict the onset and facilitate the delivery of medical countermeasures.

11C-Choline PET Guided Salvage Radiation Therapy for Isolated Pelvic and Paraortic Nodal Recurrence of Prostate Cancer After Radical Prostatectomy: Rationale and Early Genitourinary or Gastrointestinal Toxicities

Purpose

To assess gastrointestinal (GI) and genitourinary (GU) adverse events (AEs) of ¹¹C-choline-positron emission tomography (CholPET) guided lymph node (LN) radiation therapy (RT) in patients who experience biochemical failure after radical prostatectomy.

Methods and Materials

From 2013 to 2016, 107 patients experienced biochemical failure of prostate cancer, had CholPET-detected pelvic and/or paraortic LN recurrence, and were referred for RT. Patients received androgen suppression and CholPET guided LN RT (median dose, 45 Gy) with a simultaneous integrated boost to CholPET-avid sites (median dose, 56.25 Gy), all in 25 fractions. RT-naïve patients had the prostatic fossa included in the initial treatment volumes followed by a sequential boost (median dose, 68 Gy). GI and GU AEs were reported per Common Terminology Criteria for Adverse Events (version 4.0) with data gathered retrospectively. Differences in maximum GI and GU AEs at baseline, immediately post-RT, and at early (median, 4 months) and late (median, 14 months) follow-up were assessed.

Results

Median follow-up was 16 months (interquartile range [IQR], 11-25). Median prostate-specific antigen at time of positive CholPET was 2.3 ng/mL (IQR, 1.3-4.8), with a median of 2 (IQR, 1-4) choline-avid LNs per patient. Most recurrences were within the pelvis (53%) or pelvis + paraortic (40%). Baseline rates of grade 1 to 2 GI AEs were 8.4% compared with 51.9% (4.7% grade 2) of patients post-RT (P < .01). These differences resolved by 4-month (12.2%, P = .65) and 14-month AE assessments (9.1%, P = .87). There was no significant change in grade 1 to 2 GU AEs post-RT (64.1%) relative to baseline (56.0%, P = .21), although differences did arise at 4-month (72.2%, P = .01) and 14-month (74.3%, P = .01) AE assessments.

Conclusions

Salvage CholPET guided nodal RT has acceptably low rates of acute GI and GU AEs and no significant detriment in 14-month GI AEs. These data are of value in counseling patients and designing prospective trials evaluating the oncologic efficacy of this treatment strategy.

Increased utilization of external beam radiotherapy relative to cystectomy for localized, muscle-invasive bladder cancer: a SEER analysis

OBJECTIVE

To assess recent utilization patterns of radiotherapy (RT) relative to cystectomy for muscle-invasive bladder cancer (MIBC) and evaluate survival trends over time in patients receiving RT.

MATERIALS AND METHODS

The surveillance, epidemiology, and end results program (SEER) was used to identify patients diagnosed between 1992 and 2013 with localized MIBC. Patients with a prior history of non-bladder malignancy, who received no treatment, or did not have available treatment information, were excluded. Treatment utilization patterns were assessed using Cochran-Armitage tests for trend, and patient characteristics were compared using chi-square tests. Overall survival (OS) and cause-specific survival (CSS) were estimated using the Kaplan-Meier method. All-cause (ACM) and cause-specific mortality (CSM) were evaluated with multivariable Cox proportional hazards regression.

RESULTS

Of 16175 patients analyzed, 11917 (74%) underwent cystectomy, and 4258 (26%) were treated with RT. Patients who received RT were older (median age 79 vs. 68, P < 0.01). Over time, the proportion of patients receiving RT relative to cystectomy increased (24% 1992–2002 vs. 28% 2003–2013, P < 0.01), despite median patient age throughout the study period remaining unchanged (71 for each 1992–2002 and 2003–2013, P = 0.41). For RT, compared with patients diagnosed earlier, those diagnosed from 2010–2013 showed improved OS (64% vs. 60% at 1 year, P < 0.01; 38% vs. 29% at 3 years, P < 0.01) and CSS (71% vs. 67% at 1 year, P = 0.01; 51% vs. 40% at 3 years, P < 0.01). On multivariable analysis, diagnosis from 2010–2013 was associated with a lower estimated risk of ACM (hazard ratio 0.77; 95% confidence interval 0.66–0.89, P < 0.001) and CSM (hazard ratio 0.81; 95% confidence interval 0.67–0.97, P = 0.02).

CONCLUSION

Utilization of RT for localized MIBC increased relative to cystectomy from 1992 to 2013, despite the median age of treated patients remaining unchanged. More recent survival outcomes for patients receiving RT were improved, supporting continued use of bladder preservation strategies utilizing RT.

Multicenter Evaluation of the Tolerability of Combined Treatment With PD-1 and CTLA-4 Immune Checkpoint Inhibitors and Palliative Radiation Therapy

PURPOSE

To analyze immune-related adverse events (ir-AEs) in patients treated with radiation and immune checkpoint blockade.

METHODS AND MATERIALS

We retrospectively reviewed records from patients with metastatic non-small cell lung cancer, melanoma, or renal cell cancer who received at least 1 cycle of a CTLA-4 or PD-1 inhibitor and radiation. Immune-related adverse events, defined using Common Terminology Criteria for Adverse Events version 4.0, were tabulated in relation to treatment variables, and associations with sequencing and timing were assessed.

RESULTS

We identified 133 patients, of whom 28 received a CTLA-4 inhibitor alone, 88 received a PD-1 inhibitor alone, and 17 received both classes of inhibitors either sequentially (n=13) or concurrently (n=4). Fifty-six patients received radiation within 14 days of an immune checkpoint inhibitor. Forty-six patients experienced at least 1 ir-AE (34.6%). Patients receiving both CTLA-4 and PD-1 inhibitors experienced more any-grade ir-AEs as compared with either individually (71% vs 29%, P=.0008). Any-grade ir-AEs occurred in 39% of patients in whom radiation was administered within 14 days of immunotherapy, compared with 23% of other patients (P=.06) and more often in patients who received higher equivalent dose in 2-Gy fractions (EQD2) EQD2 (P=.01). However, most toxicities were mild. There were no associations between site irradiated and specific ir-AEs.

CONCLUSIONS

Our data suggest the combination of focal palliative radiation and CTLA-4 and/or PD-1 inhibitors is well tolerated, with manageable ir-AEs that did not seem to be associated with the particular site irradiated. Although conclusions are limited by the heterogeneity of patients and treatments, and future confirmatory studies are needed, this information can help guide clinical practice for patients receiving immune checkpoint therapy who require palliative radiation therapy.

Abstract A20: A systematic evaluation of abscopal responses following radiation therapy in patients with metastatic melanoma treated with ipilimumab

Purpose/Objective(s): Prior case reports and preclinical studies have suggested that combined radiotherapy and immunotherapy may generate tumor responses outside the radiation treatment field (the “abscopal effect”). However, the frequency of this phenomenon and the radiation parameters associated with its occurrence are relatively unexplored. We aimed to systemically evaluate out-of-field responses following radiotherapy in a large cohort of patients with metastatic melanoma who had been also been treated with the CTLA-4 inhibitor ipilimumab.

Materials/Methods: We retrospectively reviewed records from 91 consecutive patients with metastatic melanoma who were treated with ipilimumab and radiation therapy at our institution. These 91 patients received a total of 208 courses of palliative radiation treatment between October 2007 and June 2014. Overall survival was calculated from the date patients were diagnosed with metastatic melanoma using the Kaplan-Meier method. We reviewed radiographic imaging before and after each course of radiotherapy, and the largest “index” lesion outside the radiation treatment field was identified. The difference in the largest diameters of the index lesions were calculated comparing the pre- and post- radiation treatment imaging studies as well as two consecutive imaging studies performed immediately prior to radiotherapy. A favorable response was defined as any decrease in the size of the index lesion. We compared the number of favorable responses before and after radiation therapy using McNemar's test. We also calculated the difference in response on the two imaging studies prior to radiation as compared to before and after radiation therapy by calculating the difference between the percent changes in index lesion diameter (“delta-delta”), and analyzed the significance of these differences using the binomial test. Finally, we used Pearson's chi-squared test to assess associations between radiation treatment parameters and changes in response rate.

Results: Patient median survival was 19 months (IQR: 11-48 months, median follow up 17 months), with 5-year survival of 22%. There were 116 radiotherapy courses identified with available data from at least two consecutive imaging studies prior to initiation of radiation as well as a single post-radiation study. Index lesions shrank in 10 instances prior to radiation therapy (9%) as compared with 29 instances (25%) after radiation therapy; in 22 of these 29 instances (76%) the index lesion had been increasing in size prior to radiotherapy (p&lt;0.001). Radiotherapy was also associated with an improved rate of index lesion response (delta-delta) in 65% of cases (p=0.004). A radiation fraction size ≤3 Gy was associated with an improved rate of index lesion response as compared with hypofractionated treatment including stereotactic radiosurgery and stereotactic body radiotherapy (78% favorable as compared with 52%, p=0.016).

Conclusions: Our systematic review of metastatic melanoma patients treated with the combination of radiotherapy and ipilimumab suggests that a subset of patients may have more favorable out-of-field responses following treatment with radiation. Interestingly, we found that smaller radiation fraction sizes (≤3 Gy/fraction) were associated with a more favorable change in response. If confirmed, these results may have important ramifications for the design of future trials that seek to combine radiation and immunotherapy to maximize the likelihood of achieving an abscopal effect.

Citation Format: Ravi A. Chandra, Tyler J. Wilhite, Tracy A. Balboni, Alexander Spektor, Andrea K. Ng, Frank Stephen Hodi, Jr., Jonathan D. Schoenfeld. A systematic evaluation of abscopal responses following radiation therapy in patients with metastatic melanoma treated with ipilimumab. [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy: A New Chapter; December 1-4, 2014; Orlando, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2015;3(10 Suppl):Abstract nr A20.

A systematic evaluation of abscopal responses following radiotherapy in patients with metastatic melanoma treated with ipilimumab

Case reports and preclinical data suggest radiotherapy and immunotherapy may synergize to generate "abscopal" responses outside the radiation field. This phenomenon remains relatively unexplored, prompting our systematic evaluation of metastatic melanoma patients treated with the CTLA-4 inhibitor ipilimumab and palliative radiation therapy. We evaluated 47 consecutive metastatic melanoma patients treated with ipilimumab and 65 courses of radiation. Responses of index lesions outside the radiation field were compared before and after radiotherapy, and parameters associated with favorable response were assessed. Median survival was 28 months, with an estimated 20% 5-y survival. Index lesions shrank in 7 instances prior to radiation therapy (11%), compared with 16 instances (25%) after radiation therapy; in 11 of the latter instances (69%), the index lesion had been increasing in size prior to radiotherapy (P = 0.03). In 68% of cases, radiotherapy was associated with an improved rate of index lesion response (P = 0.006). Radiation fraction size ≤ 3 Gy was the only parameter identified associated with favorable index lesion response (P = 0.014). Our systematic review of melanoma patients treated with radiotherapy and ipilimumab suggests that a subset of patients may have more favorable out-of-field responses following treatment with radiation. Interestingly, we found that multiple fraction radiation regimens were associated with a more favorable response. These results are encouraging regarding potential synergies between radiation and immunotherapy, but suggest that attention and even prospective testing of radiation parameters critical to producing abscopal effects in human patients would be of value.

Marital status and survival in patients with cancer

PURPOSE

To examine the impact of marital status on stage at diagnosis, use of definitive therapy, and cancer-specific mortality among each of the 10 leading causes of cancer-related death in the United States.

METHODS

We used the Surveillance, Epidemiology and End Results program to identify 1,260,898 patients diagnosed in 2004 through 2008 with lung, colorectal, breast, pancreatic, prostate, liver/intrahepatic bile duct, non-Hodgkin lymphoma, head/neck, ovarian, or esophageal cancer. We used multivariable logistic and Cox regression to analyze the 734,889 patients who had clinical and follow-up information available.

RESULTS

Married patients were less likely to present with metastatic disease (adjusted odds ratio [OR], 0.83; 95% CI, 0.82 to 0.84; P < .001), more likely to receive definitive therapy (adjusted OR, 1.53; 95% CI, 1.51 to 1.56; P < .001), and less likely to die as a result of their cancer after adjusting for demographics, stage, and treatment (adjusted hazard ratio, 0.80; 95% CI, 0.79 to 0.81; P < .001) than unmarried patients. These associations remained significant when each individual cancer was analyzed (P < .05 for all end points for each malignancy). The benefit associated with marriage was greater in males than females for all outcome measures analyzed (P < .001 in all cases). For prostate, breast, colorectal, esophageal, and head/neck cancers, the survival benefit associated with marriage was larger than the published survival benefit of chemotherapy.

CONCLUSION

Even after adjusting for known confounders, unmarried patients are at significantly higher risk of presentation with metastatic cancer, undertreatment, and death resulting from their cancer. This study highlights the potentially significant impact that social support can have on cancer detection, treatment, and survival.