Molecular Subtypes and Outcomes in a Multi-Institutional Review of Rectal Cancer Patients

PURPOSE/OBJECTIVE(S)

Colorectal cancer (CRC) is a heterogeneous malignancy associated with a variety of genetic mutations. More recent data indicates that CRC can be broken down into unique biologically distinct consensus molecular subtypes (CMS) based on different pathological and genetic signatures. The purpose of this study is to evaluate the outcomes of rectal cancer patients in a multi-institutional network based on tumor mutational assessment and CMS group.

MATERIALS/METHODS

Patient exome and transcriptome sequencing data and clinical outcomes were collected under the Total Cancer Care Protocol and Avatar® project within the Oncology Research Information Exchange Network (ORIEN). A total of 101 patients with demographic and outcomes information had data for microsatellite instability (MSI), tumor mutation burden (TMB), transcriptome, and whole exome sequencing (WES). Molecular subclasses (CMS1, CMS2, CMS3, CMS4, CMS-Mixed) were assigned based on transcriptional signatures by the R package "CMS Caller." Survival analysis was performed with the R packages "Survival" and "Survminer."

RESULTS

A total of 101 rectal cancer patients, with a median age of 56.8, had a median follow up of 3.5 years (range 0.26-23.5). 78 patients were treated with curative intent for clinically localized disease and 35% of these patients developed metastatic disease. The remaining 23 patients had synchronous metastatic disease at presentation. There were 5 (5%) CMS1, 29 (29%) CMS2, 13 (13%) CMS 3, 49 (49%) CMS 4, and 5 (5%) CMS-Mixed patients in our cohort respectively. The cohort included 5 (5%) BRAF, 51 (50%) KRAS, and 63 (62%) TP53 mutated patients and 5 (5%) MSI high patients. Median survival was 18.8, 117.2, 125.7 and 119 months for CMS1, CMS2, CMS3, and CMS4 patients respectively, with insufficient events in CMS-mixed for calculation (p = 0.15). CMS1 patients had a significantly shorter survival compared to the other cohorts (p = 0.02), with 2 of 5 of these patients having received immunotherapy. 40% (2,0) CMS1, 52% (7,8) of CMS2, 15% (1,1) of CMS3, 59% (13,15) of CMS4, and 40% (1,1) of CMS-Mixed presented with or developed metastatic disease respectively. When divided into mutation groups, median survival was 43 versus 119, 119 versus 117, and 126 versus 119 months for BRAF, KRAS, and TP53 mutated and wild type patients respectively (p = 0.18, p = 0.48, p = 0.93). Evaluation of TMB and MSI status did not reveal significant differences in outcomes (p = 0.54, p = 0.7), with median survival of 126 months versus 117 in TMB high versus low patients and unreached versus 119 months in MSI versus MSS patients respectively. Of note, 3 of the 5 MSI patients were also CMS1, with the other two coming from CMS4 and CMS-mixed cohorts.

CONCLUSION

CMS classification and tumor mutation status are associated with differential outcomes for rectal cancer patients, with some groups having a large likelihood of developing metastatic disease. Further work on optimizing and personalizing treatments for these high-risk populations is necessary.

Initial Report of a Randomized Trial Comparing Conventional vs. Novel Treatment Planning Technique to Ameliorate Immunosuppression from Lung SBRT

PURPOSE/OBJECTIVE(S)

SBRT is highly effective against early-stage non-small cell lung cancer. Radiation Therapy (RT) is known to modulate the immune system and contribute to the generation of anti-tumor T cells and stimulate T cell infiltration into tumors. However, this anti-tumor activity is offset by radiation-induced immunosuppression (RIIS) which results in lower tumor control and survival. Lymphocytes are highly radiosensitive and RIIS means destroying existing as well as newly created cytotoxic and helper T lymphocytes. We hypothesized that optimizing RT treatment planning by considering circulating blood and lymphatics as a critical Organ at Risk (OAR) may mitigate RIIS.

MATERIALS/METHODS

We conducted an IRB approved NCI funded clinical trial for 50 early-stage lung cancer patients treated with SBRT alone, from 2020 to 2023, to investigate the ability to reduce RIIS by reducing dose to circulating blood and lymphatics with the aid of a predictive algorithm. All SBRT plans adhered to treatment parameters from RTOG 0813 (central) or RTOG 0915 (peripheral). Patients were randomized to two arms: experimental optimization for RIIS (to reduce dose to blood and lymphatic rich organs) versus standard SBRT planning (without optimization for RIIS). Peripheral blood samples were collected at baseline, end of Tx, 4 weeks and 6 months post Tx. Patients with baseline absolute lymphocyte counts (ALC) less than 0.5x109 cells/L were ineligible for the trial. Data acquired for all blood cell types as well as lymphocyte sub populations CD3+, CD4+, CD8+, CD19+, CD56+. Two sample t-test was used to determine the statistical significance between the cohorts at the time points.

RESULTS

The standard arm had an ALC reduction of 28% at one week post Tx and a nadir at 4 weeks with a 34% reduction. Absolute percentage reductions in ALC from baseline in the optimized arm compared to the standard arm are: end of treatment point (13%, p = 0.03), 4 weeks (12%, p = 0.08), 6 months (15%, p = 0.1), and all three time points together 13% (p = 0.001). ALC recovery appears to be faster in the optimized arm. Radiation induced suppression of all blood cell types are also reduced in the optimized arm with respect to standard arm (relative percentages): ALC (34%), WBC (47%), RBC (46%), platelets (40%), monocytes (100%), and neutrophils (62%) at 4-week mark. Average percentage reductions on integral doses, and V5 (volume receiving a 5 Gy dose) of optimized compared to standard plans are: aorta: 26%, 41% heart: 8%, 33%, vena cava: 32%, 52%, T spine: 51%, 81%, lymph nodes: 35%, 57%, total lung- ITV: 1.6%, 1%, body: 10%, 14%.

CONCLUSION

For the first time, we have shown that it is possible to reduce RIIS in a statistically significant manner, compared to standard of care, via optimized RT planning using a predictive model. This has implications in increasing the efficacy of immunotherapy by preserving the existing tumor reactive T cells in the immune system to enhance anti-tumor activity, and in reducing hospitalizations and improving survival.

Influence of cultural conditions on growth and lipolytic activity in Nocardia asteroides

The growth and the production of extracellular and intracellular lipases were measured from Nocardia asteroides grown under different cultural conditions. Maximal growth and intracellular and extracellular activities were observed at 3 d after inoculation. Among the tested media, synthetic medium induced maximal growth and extracellular activity, whereas tryptic soy broth induced the maximal intracellular lipase activity. The best carbon and nitrogen sources for growth and lipolytic activity were glucose, fructose, glutamate and nitrate, respectively. The optimal C:N ratio for growth was in the range of 1:4 to 2:3 and for lipase activity the range was 2:3 to 3:2. Anything above or below this range was detrimental to the organism and its enzyme activity. Under the conditions of this study, N. asteroides grew best and had the highest lipase activity when compared to N. brasiliensis and N. caviae.