Resection Cavity Contraction Effects in the Use of Radioactive Sources (1-25 versus Cs-131) for Intra-Operative Brain Implants

Background and Objectives Intra-parenchymal brain surgical resection cavities usually contract in volume following low dose rate (LDR) brachytherapy implants. In this study, we systematically modeled and assessed dose variability resulting from such changes for I-125 versus Cs-131 radioactive sources. Methods Resection cavity contraction was modeled based on 95 consecutive patient cases, using surveillance magnetic resonance (MR) images. The model was derived for single point source geometry and then fully simulated in 3D where I-125 or Cs-131 seeds were placed on the surface of an ellipsoidal resection cavity. Dose distribution estimated via TG-43 calculations and biological effective dose (BED) calculations were compared for both I-125 and Cs-131, accounting for resection cavity contractions. Results Resection cavity volumes were found to contract with an effective half-life of approximately 3.4 months (time to reach 50% of maximum volume contraction). As a result, significant differences in dose distributions were noted between I-125 and Cs-131 radioactive sources. For example, when comparing with static volume, assuming no contraction effect, I-125 exhibited a 31.8% and 30.5% increase in D90 and D10 values (i.e., the minimal dose to 90% and 10% of the volume respectively) in the peripheral target areas over the follow-up period of 20.5 months. In contrast, Cs-131 seeds only exhibited a 1.44% and 0.64% increase in D90 and D10 values respectively. Such discrepancy is likewise similar for BED calculations. Conclusion Resection cavity contractions affects Cs-131 dose distribution significantly less than that of I-125 for permanent brain implants. Care must be taken to account for cavity contractions when prescribing accumulative doses of a radioactive source in performing the brain implant procedures.

Correlation between small-volume spinal cord doses for spine stereotactic body radiotherapy (SBRT)

PURPOSE

Doses to small spinal cord isodose volume (such as those ranging from Dmax 0.0 cc to 0.5 cc) as well as to large volumes (such as those ranging from 0.5 cc to 3.0 cc) are critical parameters to guide safe practice of spine SBRT. We here report a mathematical formula that links the most probable dose volume limits together for common spine SBRT cases.Methods and materials: A dose ripple formula parameterized with equivalent dose radius (EDR) was derived to model spinal cord small-volume doses for a spine SBRT treatment. A cohort of spine SBRT cases (n=68), treated with either a robotic x-band linac or a conventional S-band linac, was selected to verify the model predictions. The mean prescription dose was 22± 4 Gy (range, 12-40 Gy) delivered in 2±1 fractions. The mean and median target volume was 39.4±42.5 cc and 30.3 cc (range, 0.24-264.2 cc), respectively. Direct correlations between the spinal cord Dmax and variable spinal cord doses of increasing isodose volumes (ranging from 0.0 cc to 3.0 cc) of different planning organ-at-risk volumes (PRVs) were investigated. The PRV structures for the study included the true cord, thecal sac and the true cord plus variable margins ranging from 1.0 mm to 3.0 mm.

RESULTS

No direct linear correlation was observed amongst the small volume doses to the spinal cord PRVs. However, strong linear correlations (R² > 0.96) for all the studied PRVs were observed when correlating EDRs amongst isodose volumes ranging from 0.0 cc to 3.0 cc. In particular, EDR dependence was found to differ significantly for the thecal sac versus the spinal cord with or without 1-3 millimeter margins. With strong EDR correlation, the most probable relationship among the small-volume dose limits was derived for the spinal cord PRVs.

CONCLUSION

An analytical formula linked the most probable pin-point/small isodose volume doses with relatively large isodose volume doses of the spinal cord for spine SBRT. As a result, a small number of dose limits such as Dmax or D(0.35cc) are likely sufficient to surrogate the spinal cord dose tolerance for consistent treatment planning optimization and outcome analysis.

Expert consensus on re-irradiation for recurrent glioma

Purpose

To investigate radiation oncologists’ opinions on important considerations to offering re-irradiation (re-RT) as a treatment option for recurrent glioma.

Materials and methods

A survey was conducted with 13 radiation oncologists involved in the care of central nervous system tumor patients. The survey was comprised of 49 questions divided into 2 domains: a demographic section (10 questions) and a case section (5 re-RT cases with 5 to 6 questions representing one or several re-RT treatment dilemmas as may be encountered in the clinic). Respondents were asked to rate the relevance of various factors to offering re-RT, respond to the cases with a decision to offer re-RT vs. not, volume to be treated, margins to be employed, dose/fractionation suggested and any additional comments with respect to rationale in each scenario.

Results

Sixty nine percent of responders have been practicing for greater than 10 years and 61% have re-RT 20 to 100 patients to date, with 54% seeing 2–5 re-RT cases per month and retreating 1–2 patients per month. Recurrent tumor volume, time since previous radiation therapy, previously administered dose to organs at risk and patient performance status were rated by the majority of responders (85%, 92%, 77%, and 69% respectively) as extremely relevant or very relevant to offering re-RT as an option.

Conclusion

The experts’ practice of re-RT is still heterogeneous, reflecting the paucity of high-quality prospective data available for decision-making. Nevertheless, practicing radiation oncologists can support own decisions by referring to the cases found suitable for re-RT in this survey.

Electronic supplementary material

The online version of this article (10.1186/s13014-017-0928-3) contains supplementary material, which is available to authorized users.

Estimating Survival in Melanoma Patients With Brain Metastases: An Update of the Graded Prognostic Assessment for Melanoma Using Molecular Markers (Melanoma-molGPA)

PURPOSE

To update the Diagnosis-Specific Graded Prognostic Assessment (DS-GPA) for a markedly heterogeneous patient population, patients with melanoma and brain metastases, using a larger, more current cohort, including molecular markers.

METHODS

The original Melanoma-GPA is based on data from 483 patients whose conditions were diagnosed between 1985 and 2005. This is a multi-institutional retrospective database analysis of 823 melanoma patients with newly diagnosed brain metastases from January 1, 2006, to December 31, 2015. Multivariable analyses identified significant prognostic factors, which were weighted and included in the updated index (Melanoma-molGPA). Multiple Cox regression was used to select and weight prognostic factors in proportion to their hazard ratios to design the updated Melanoma-molGPA in which scores of 4.0 and 0.0 are associated with the best and worst prognoses, as with all of the diagnosis-specific GPA indices. Log-rank tests were used to compare adjacent classes.

RESULTS

There were 5 significant prognostic factors for survival (age, Karnofsky performance status [KPS], extracranial metastases [ECM], number of brain metastases, and BRAF status), whereas only KPS and the number of brain metastases were significant in the original Melanoma-GPA. Median survival improved from 6.7 to 9.8 months between the 2 treatment eras, and the median survival times for patients with Melanoma-molGPA of 0 to 1.0, 1.5 to 2.0, 2.5 to 3.0, and 3.5 to 4.0 were 4.9, 8.3, 15.8, and 34.1 months (P<.0001 between each adjacent group).

CONCLUSIONS

Survival and our ability to estimate survival in melanoma patients with brain metastases has improved significantly. The updated Melanoma-molGPA, a user-friendly tool to estimate survival, will facilitate clinical decision making regarding whether and which treatment is appropriate and will also be useful for stratification of future clinical trials. To further simplify use, a free online/smart phone app is available at brainmetgpa.com.

Indications and Efficacy of Gamma Knife Stereotactic Radiosurgery for Recurrent Glioblastoma: 2 Decades of Institutional Experience

BACKGROUND

The role of stereotactic radiosurgery (SRS) for recurrent glioblastoma and the radionecrosis risk in this setting remain unclear.

OBJECTIVE

To perform a large retrospective study to help inform proper indications, efficacy, and anticipated complications of SRS for recurrent glioblastoma.

METHODS

We retrospectively analyzed patients who underwent Gamma Knife SRS between 1991 and 2013. We used the partitioning deletion/substitution/addition algorithm to identify potential predictor covariate cut points and Kaplan-Meier and proportional hazards modeling to identify factors associated with post-SRS and postdiagnosis survival.

RESULTS

One hundred seventy-four glioblastoma patients (median age, 54.1 years) underwent SRS a median of 8.7 months after initial diagnosis. Seventy-five percent had 1 treatment target (range, 1-6), and median target volume and prescriptions were 7.0 cm 3 (range, 0.3-39.0 cm 3 ) and 16.0 Gy (range, 10-22 Gy), respectively. Median overall survival was 10.6 months after SRS and 19.1 months after diagnosis. Kaplan-Meier and multivariable modeling revealed that younger age at SRS, higher prescription dose, and longer interval between original surgery and SRS are significantly associated with improved post-SRS survival. Forty-six patients (26%) underwent salvage craniotomy after SRS, with 63% showing radionecrosis or mixed tumor/necrosis vs 35% showing purely recurrent tumor. The necrosis/mixed group had lower mean isodose prescription compared with the tumor group (16.2 vs 17.8 Gy; P = .003) and larger mean treatment volume (10.0 vs 5.4 cm 3 ; P = .009).

CONCLUSION

Gamma Knife may benefit a subset of focally recurrent patients, particularly those who are younger with smaller recurrences. Higher prescriptions are associated with improved post-SRS survival and do not seem to have greater risk of symptomatic treatment effect.

Estimating Survival in Patients With Lung Cancer and Brain Metastases: An Update of the Graded Prognostic Assessment for Lung Cancer Using Molecular Markers (Lung-molGPA)

Importance

Lung cancer is the leading cause of cancer-related mortality in the United States and worldwide. As systemic therapies improve, patients with lung cancer live longer and thus are at increased risk for brain metastases. Understanding how prognosis varies across this heterogeneous patient population is essential to individualize care and design future clinical trials.

Objective

To update the current Diagnosis-Specific Graded Prognostic Assessment (DS-GPA) for patients with non-small-cell lung cancer (NSCLC) and brain metastases. The DS-GPA is based on data from patients diagnosed between 1985 and 2005, and we set out to update it by incorporating more recently reported gene and molecular alteration data for patients with NSCLC and brain metastases. This new index is called the Lung-molGPA.

Design, Setting, and Participants

This is a multi-institutional retrospective database analysis of 2186 patients diagnosed between 2006 and 2014 with NSCLC and newly diagnosed brain metastases. The multivariable analyses took place between December 2015 and May 2016, and all prognostic factors were weighted for significance by hazard ratios. Significant factors were included in the updated Lung-molGPA prognostic index.

Main Outcomes and Measures

The main outcome was survival. Multiple Cox regression was used to select and weight prognostic factors in proportion to their hazard ratios. Log rank tests were used to compare adjacent classes and to compare overall survival for adenocarcinoma vs nonadenocarcinoma groups.

Results

The original DS-GPA was based on 4 factors found in 1833 patients with NSCLC and brain metastases diagnosed between 1985 and 2005: patient age, Karnofsky Performance Status, extracranial metastases, and number of brain metastases. The patients studied for the creation of the DS-GPA had a median survival of 7 months from the time of initial treatment of brain metastases. To design the updated Lung-molGPA, we analyzed data from 2186 patients from 2006 through 2014 with NSCLC and newly diagnosed brain metastases (1521 adenocarcinoma and 665 nonadenocarcinoma). Significant prognostic factors included the original 4 factors used in the DS-GPA index plus 2 new factors: EGFR and ALK alterations in patients with adenocarcinoma (mutation status was not routinely tested for nonadenocarcinoma). The overall median survival for the cohort in the present study was 12 months, and those with NSCLC-adenocarcinoma and Lung-molGPA scores of 3.5 to 4.0 had a median survival of nearly 4 years.

Conclusions and Relevance

In recent years, patient survival and physicians' ability to predict survival in NSCLC with brain metastases has improved significantly. The updated Lung-molGPA incorporating gene alteration data into the DS-GPA is a user-friendly tool that may facilitate clinical decision making and appropriate stratification of future clinical trials.

Case-based review: pediatric medulloblastoma

Medulloblastoma is the most common malignant brain tumor affecting children. These tumors are high grade with propensity to metastasize within the central nervous system and, less frequently, outside the neuraxis. Recent advancements in molecular subgrouping of medulloblastoma refine diagnosis and improve counseling in regards to overall prognosis. Both are predicated on the molecular drivers of each subgroup-WNT-activated, SHH-activated, group 3, and group 4. The traditional therapeutic mainstay for medulloblastoma includes a multimodal approach with surgery, radiation, and multiagent chemotherapy. As we discover more about the molecular basis of medulloblastoma, efforts to adjust treatment approaches based on molecular risk stratification are under active investigation. Certainly, the known neurological, developmental, endocrine, and psychosocial injury related to medulloblastoma and its associated therapies motivate ongoing research towards improving treatment for this life-threatening tumor while at the same time minimizing long-term side effects.

Patient-Specific Fetal Dose Determination for Multi-Target Gamma Knife Radiosurgery: Computational Model and Case Report

A 42-year-old woman at 29 weeks gestation via in vitro fertilization who presented with eight metastatic brain lesions received Gamma Knife stereotactic radiosurgery (GKSRS) at our institution. In this study, we report our clinical experience and a general procedure of determining the fetal dose from patient-specific treatment plans and we describe quality assurance measurements to guide the safe practice of multi-target GKSRS of pregnant patients. To estimate fetal dose pre-treatment, peripheral dose-to-focal dose ratios (PFRs) were measured in a phantom at the distance approximating the fundus of uterus. Post-treatment, fetal dose was calculated from the actual patient treatment plan. Quality assurance measurements were carried out via the extrapolation dosimetry method in a head phantom at increasing distances along the longitudinal axis. The measurements were then empirically fitted and the fetal dose was extracted from the curve. The computed and measured fetal dose values were compared with each other and associated radiation risk was estimated. Based on low estimated fetal dose from preliminary phantom measurements, the patient was accepted for GKSRS. Eight brain metastases were treated with prescription doses of 15-19 Gy over 143 min involving all collimator sizes as well as composite sector mixed shots. Direct fetal dose computation based on the actual patient’s treatment plan estimated a maximum fetal dose of 0.253 cGy, which was in agreement with surface dose measurements at the level of the patient’s uterine fundus during the actual treatment. Later phantom measurements also estimated fetal dose to be in the range of 0.21-0.28 cGy (dose extrapolation curve R² = 0.998). Using the National Council on Radiation Protection and Measurements (NCRP) population-based model, we estimate the fetal risk of secondary malignancy, which is the primary toxicity after 25 weeks gestation, to be less than 0.01%. Of note, the patient delivered the baby via scheduled cesarean section at 36 weeks without complications attributable to the GKSRS procedure. GKSRS of multiple brain metastases was demonstrated to be safe and feasible during pregnancy. The applicability of a general patient-specific fetal dose determination method was also demonstrated for the first time for such a treatment.

Abstract 1356: Variable drug responses characterize the functional heterogeneity of Nf1 null tumors

Introduction: Neurofibromatosis type 1 (NF1) is a autosomal dominant disease with a predisposition to cancer. Biallelic inactivation of the NF1 gene increases risk of developing brain tumors, leukemia, neurofibromas and malignant peripheral nerve sheath tumors (MPNSTs). Somatic mutations in the NF1 gene are also associated with sporadic malignancies including glioblastoma, neuroblastoma, and melanoma. The NF1 tumor suppressor gene encodes the RAS GTPase-activating protein (GAP) neurofibromin. Loss of NF1 results hyperactivation of Ras, MAPK and PI3K signaling pathways components, representing potential therapeutic targets. However, the variable response of NF1 mutant tumors to MAPK and mTOR inhibitors suggests the intrinsic heterogeneity of NF1 mutant tumors. We hypothesized that defining alternative mechanisms and functional sub-classes of Nf1-mutant tumors on the basis of their variable drug sensitivity will produce pre-clinical therapeutics data that will inform clinical trials.

Methods: We previously generated mouse models in which we mutagenized Nf1 heterozygous mice with radiation, recapitulating the susceptibility of patients with NF1 to radiation-induced cancers. These models produced solid tumors such as mammary carcinomas, squamous cell carcinomas, and soft tissue sarcomas, which we determined to be Nf1 null. Cell lines established from these tumors were characterized by a drug sensitivity screen using a custom 94 compound drug library. Drug responses indicate that Nf1 mutant tumor cell lines organize into functional groups sharing similar drug sensitivities. Six candidate drugs each targeting distinct components of MAPK and PI3K signaling pathways were selected from the drug library. After 24 hours of exposure to each inhibitor or control, cells were analyzed for cell proliferation, cell cycle changes, and cell death. Western blotting were performed to determine whether drug exposures produce alterations in their predicted biochemical pathways such as PI3K/Akt, and MAPK pathways.

Results: Nf1 loss did not predict uniform sensitivity of cell lines to treatment with MAPK and mTOR inhibitors. Each compound induced differential effects on viability of Nf1 null tumors cell lines. High variability and cell line-dependent cytotoxic and cytostatic effects were also observed. Although phosphorylated Akt(S473), S6, and p44/42 MAPK varied widely among all untreated Nf1 null cell lines, this did not predict their drug sensitivity. In vitro drug sensitivity data indicates heterogeneous differential sensitivities of Nf1 mutant tumor cells to different drug classes, independent of tumor histology, permitting segregation into functional groups.

Conclusion: Tumor cell lines driven by Nf1 loss demonstrate heterogeneous responses to Ras pathway inhibition, which may be explained by mechanisms of tumor formation after Nf1 loss involve multiple alternative pathways.

Citation Format: Daniela Pucciarelli, Ganesh Krishnamurthi, Steve Braunstein, Jean L. Nakamura. Variable drug responses characterize the functional heterogeneity of Nf1 null tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1356. doi:10.1158/1538-7445.AM2017-1356

The Prognostic Value of BRAF, C-KIT, and NRAS Mutations in Melanoma Patients With Brain Metastases

PURPOSE

Brain metastases are a common problem in patients with melanoma, but little is known about the effect of gene mutations on survival in these patients.

METHODS AND MATERIALS

We created a retrospective multi-institutional database of 823 patients with melanoma and brain metastases diagnosed between 2006 and 2015. Clinical parameters, gene mutation status (BRAF, C-KIT, NRAS), and treatment were correlated with survival. Treatment patterns and outcomes were compared with a prior era (1985-2005).

RESULTS

BRAF status was known in 584 of 823 patients (71%). BRAF, NRAS, and C-KIT mutations were present in 51%, 22%, and 11% of tested patients, respectively. The median time from primary diagnosis to brain metastasis was 32 months, and overall median survival (MS) from the time of initial treatment of brain metastases was 10 months. MS for BRAF-positive and BRAF-negative patients was 13 months and 9 months, respectively (P=.02). There was no significant difference in MS in patients with or without NRAS or C-KIT mutations. The time from primary diagnosis to brain metastasis did not vary by mutation and was not associated with survival after the diagnosis of brain metastases. MS for the 1985 to 2005 and 2006 to 2015 cohorts was 6.7 months and 10.0 months, respectively (P<.01). Reflecting treatment-trend changes, use of whole-brain radiation therapy decreased from 48% to 26% during this period. Among BRAF-positive patients, 71% received targeted BRAF and/or MEK inhibitors and 57% received some combination of targeted therapy, chemotherapy, and/or immunotherapy.

CONCLUSIONS

For melanoma patients with brain metastases, BRAF-positive patients survive longer than BRAF-negative patients and overall survival has improved from 1985-2005 to 2006-2015.

Impact of Neuroradiology-Based Peer Review on Head and Neck Radiotherapy Target Delineation

BACKGROUND AND PURPOSE

While standard guidelines assist in target delineation for head and neck radiation therapy planning, the complex anatomy, varying patterns of spread, unusual or advanced presentations, and high risk of treatment-related toxicities produce continuous interpretive challenges. In 2007, we instituted weekly treatment planning quality assurance rounds as a joint enterprise of head and neck radiation oncology and neuroradiology. Here we describe its impact on head and neck radiation therapy target delineation.

MATERIALS AND METHODS

For 7 months, treatment planning quality assurance included 80 cases of definitive (48%) or postoperative (52%) head and neck radiation therapy. The planning CT and associated target volumes were reviewed in comparison with diagnostic imaging studies. Alterations were catalogued.

RESULTS

Of the 80 cases, 44 (55%) were altered, and of these, 61% had clinically significant changes resulting in exclusion or inclusion of a distinct area or structure. Reasons for alteration included the following: gross or extant tumor, 26/44 (59%); elective or postoperative coverage, 25/44 (57%); lymph nodes, 13/44 (30%); bone, 7/44 (16%); skull base, 7/44 (16%); normal organs, 5/44 (11%); perineural, 3/44 (7%); distant metastasis, 2/44 (5%); and eye, 1/44 (2%). Gross tumor changes ranged from 0.5% to 133.64%, with a median change in volume of 5.95 mm³ (7.86%). Volumes were more likely to be increased (73%) than decreased (27%).

CONCLUSIONS

A collaborative approach to head and neck treatment planning quality assurance has an impact. Cases likely to have challenging patterns of infiltrative, intracranial, nodal, orbital, or perineural spread warrant intensive imaging-based review in collaboration with a diagnostic neuroradiologist.

Medical Student Knowledge of Oncology and Related Disciplines: a Targeted Needs Assessment

Despite increasing numbers of cancer survivors, non-oncology physicians report discomfort and little training regarding oncologic and survivorship care. This pilot study assesses medical student comfort with medical oncology, surgical oncology, radiation oncology, hospice/palliative medicine, and survivorship care. A survey was developed with input from specialists in various fields of oncologic care at a National Cancer Institute-designated comprehensive cancer center. The survey included respondent demographics, reports of experience with oncology, comfort ratings with oncologic care, and five clinical vignettes. Responses were yes/no, multiple choice, Likert scale, or free response. The survey was distributed via email to medical students (MS1-4) at two US medical schools. The 105 respondents were 34 MS1s (32 %), 15 MS2s and MD/PhDs (14 %), 26 MS3s (25 %), and 30 MS4s (29 %). Medical oncology, surgical oncology, and hospice/palliative medicine demonstrated a significant trend for increased comfort from MS1 to MS4, but radiation oncology and survivorship care did not. MS3s and MS4s reported the least experience with survivorship care and radiation oncology. In the clinical vignettes, students performed the worst on the long-term chemotherapy toxicity and hospice/palliative medicine questions. Medical students report learning about components of oncologic care, but lack overall comfort with oncologic care. Medical students also fail to develop an increased self-assessed level of comfort with radiation oncology and survivorship care. These pilot results support development of a formalized multidisciplinary medical school oncology curriculum at these two institutions. An expanded national survey is being developed to confirm these preliminary findings.

Discovery of additional brain metastases on the day of stereotactic radiosurgery: risk factors and outcomes

OBJECTIVE High-resolution double-dose gadolinium-enhanced Gamma Knife (GK) radiosurgery-planning MRI (GK MRI) on the day of GK treatment can detect additional brain metastases undiagnosed on the prior diagnostic MRI scan (dMRI), revealing increased intracranial disease burden on the day of radiosurgery, and potentially necessitating a reevaluation of appropriate management. The authors identified factors associated with detecting additional metastases on GK MRI and investigated the relationship between detection of additional metastases and postradiosurgery patient outcomes. METHODS The authors identified 326 patients who received GK radiosurgery at their institution from 2010 through 2013 and had a prior dMRI available for comparison of numbers of brain metastases. Factors predictive of additional brain metastases on GK MRI were investigated using logistic regression analysis. Overall survival was estimated by Kaplan-Meier method, and postradiosurgery distant intracranial failure was estimated by cumulative incidence measures. Multivariable Cox proportional hazards model and Fine-Gray regression modeling assessed potential risk factors of overall survival and distant intracranial failure, respectively. RESULTS The mean numbers of brain metastases (SD) on dMRI and GK MRI were 3.4 (4.2) and 5.8 (7.7), respectively, and additional brain metastases were found on GK MRI in 48.9% of patients. Frequencies of detecting additional metastases for patients with 1, 2, 3-4, and more than 4 brain metastases on dMRI were 29.5%, 47.9%, 55.9%, and 79.4%, respectively (p < 0.001). An index brain metastasis with a diameter greater than 1 cm on dMRI was inversely associated with detecting additional brain metastases, with an adjusted odds ratio of 0.57 (95% CI 0.4-0.9, p = 0.02). The median time between dMRI and GK MRI was 22 days (range 1-88 days), and time between scans was not associated with detecting additional metastases. Patients with additional brain metastases did not have larger total radiosurgery target volumes, and they rarely had an immediate change in management (abortion of radiosurgery or addition of whole-brain radiation therapy) due to detection of additional metastases. Patients with additional metastases had a higher incidence of distant intracranial failure than those without additional metastases (p = 0.004), with an adjusted subdistribution hazard ratio of 1.4 (95% CI 1.0-2.0, p = 0.04). Significantly worse overall survival was not detected for patients with additional brain metastases on GK MRI (log-rank p = 0.07), with the relative adjusted hazard ratio of 1.07, (95% CI 0.81-1.41, p = 0.65). CONCLUSIONS Detecting additional brain metastases on GK MRI is strongly associated with the number of brain metastases on dMRI and inversely associated with the size of the index brain metastasis. The discovery of additional brain metastases at time of GK radiosurgery is very unlikely to lead to aborting radiosurgery but is associated with a higher incidence of distant intracranial failure. However, there is not a significant difference in survival. ▪ CLASSIFICATION OF EVIDENCE Type of question: prognostic; study design: retrospective cohort trial; evidence: Class IV.

The Effect of Gene Alterations and Tyrosine Kinase Inhibition on Survival and Cause of Death in Patients With Adenocarcinoma of the Lung and Brain Metastases

PURPOSE

Lung cancer remains the most common cause of both cancer mortality and brain metastases (BM). The purpose of this study was to assess the effect of gene alterations and tyrosine kinase inhibition (TKI) on median survival (MS) and cause of death (CoD) in patients with BM from lung adenocarcinoma (L-adeno).

METHODS

A multi-institutional retrospective database of patients with L-adeno and newly diagnosed BM between 2006 and 2014 was created. Demographics, gene alterations, treatment, MS, and CoD were analyzed. The treatment patterns and outcomes were compared with those in prior trials.

RESULTS

Of 1521 L-adeno patients, 816 (54%) had known alteration status. The gene alteration rates were 29%, 10%, and 26% for EGFR, ALK, and KRAS, respectively. The time from primary diagnosis to BM for EGFR-/+ was 10/15 months (P=.02) and for ALK-/+ was 10/20 months (P<.01), respectively. The MS for the group overall (n=1521) was 15 months. The MS from first treatment for BM for EGFR and ALK-, EGFR+, ALK+ were 14, 23 (P<.01), and 45 (P<.0001) months, respectively. The MS after BM for EGFR+ patients who did/did not receive TKI before BM was 17/30 months (P<.01), respectively, but the risk of death was not statistically different between TKI-naïve patients who did/did not receive TKI after the diagnosis of BM (EGFR/ALK hazard ratios: 1.06 [P=.84]/1.60 [P=.45], respectively). The CoD was nonneurologic in 82% of patients with known CoD.

CONCLUSION

EGFR and ALK gene alterations are associated with delayed onset of BM and longer MS relative to patients without these alterations. The CoD was overwhelmingly nonneurologic in patients with known CoD.