Prediction of Overall Disease Burden in (y)pN1 Breast Cancer Using Knowledge-Based Machine Learning Model.

BACKGROUND: We aimed to construct an expert knowledge-based Bayesian network (BN) model for assessing the overall disease burden (ODB) in (y)pN1 breast cancer patients and compare ODB across arms of ongoing trials. METHODS: Utilizing institutional data and expert surveys, we developed a BN model for (y)pN1 breast cancer. Expert-derived probabilities and disability weights for radiotherapy-related benefit (e.g., 7-year disease-free survival [DFS]) and toxicities were integrated into the model. ODB was defined as the sum of disability weights multiplied by probabilities. In silico predictions were conducted for Alliance A011202, PORT-N1, RAPCHEM, and RT-CHARM trials, comparing ODB, 7-year DFS, and side effects. RESULTS: In the Alliance A011202 trial, 7-year DFS was 80.1% in both arms. Axillary lymph node dissection led to higher clinical lymphedema and ODB compared to sentinel lymph node biopsy with full regional nodal irradiation (RNI). In the PORT-N1 trial, the control arm (whole-breast irradiation [WBI] with RNI or post-mastectomy radiotherapy [PMRT]) had an ODB of 0.254, while the experimental arm (WBI alone or no PMRT) had an ODB of 0.255. In the RAPCHEM trial, the radiotherapy field did not impact the 7-year DFS in ypN1 patients. However, there was a mild ODB increase with a larger irradiation field. In the RT-CHARM trial, we identified factors associated with the major complication rate, which ranged from 18.3% to 22.1%. CONCLUSIONS: The expert knowledge-based BN model predicted ongoing trial outcomes, validating reported results and assumptions. In addition, the model demonstrated the ODB in different arms, with an emphasis on quality of life.

Assessment of lymph node area coverage with total marrow irradiation and implementation of total marrow and lymphoid irradiation using automated deep learning-based segmentation.

BACKGROUND: Total marrow irradiation (TMI) and total marrow and lymphoid irradiation (TMLI) have the advantages. However, delineating target lesions according to TMI and TMLI plans is labor-intensive and time-consuming. In addition, although the delineation of target lesions between TMI and TMLI differs, the clinical distinction is not clear, and the lymph node (LN) area coverage during TMI remains uncertain. Accordingly, this study calculates the LN area coverage according to the TMI plan. Further, a deep learning-based model for delineating LN areas is trained and evaluated. METHODS: Whole-body regional LN areas were manually contoured in patients treated according to a TMI plan. The dose coverage of the delineated LN areas in the TMI plan was estimated. To train the deep learning model for automatic segmentation, additional whole-body computed tomography data were obtained from other patients. The patients and data were divided into training/validation and test groups and models were developed using the "nnU-NET" framework. The trained models were evaluated using Dice similarity coefficient (DSC), precision, recall, and Hausdorff distance 95 (HD95). The time required to contour and trim predicted results manually using the deep learning model was measured and compared. RESULTS: The dose coverage for LN areas by TMI plan had V100% (the percentage of volume receiving 100% of the prescribed dose), V95%, and V90% median values of 46.0%, 62.1%, and 73.5%, respectively. The lowest V100% values were identified in the inguinal (14.7%), external iliac (21.8%), and para-aortic (42.8%) LNs. The median values of DSC, precision, recall, and HD95 of the trained model were 0.79, 0.83, 0.76, and 2.63, respectively. The time for manual contouring and simply modified predicted contouring were statistically significantly different. CONCLUSIONS: The dose coverage in the inguinal, external iliac, and para-aortic LN areas was suboptimal when treatment is administered according to the TMI plan. This research demonstrates that the automatic delineation of LN areas using deep learning can facilitate the implementation of TMLI.

Estimating the risk and benefit of radiation therapy in (y)pN1 stage breast cancer patients: A Bayesian network model incorporating expert knowledge (KROG 22-13).

BACKGROUND: We aimed to evaluate the risk and benefit of (y)pN1 breast cancer patients in a Bayesian network model. METHOD: We developed a Bayesian network (BN) model comprising three parts: pretreatment, intervention, and risk/benefit. The pretreatment part consisted of clinical information from a tertiary medical center. The intervention part regarded the field of radiotherapy. The risk/benefit component encompasses radiotherapy (RT)-related side effects and effectiveness, including factors such as recurrence, cardiac toxicity, lymphedema, and radiation pneumonitis. These factors were evaluated in terms of disability weights and probabilities from a nationwide expert survey. The overall disease burden (ODB) was calculated as the sum of the probability multiplied by the disability weight. A higher value of ODB indicates a greater disease burden for the patient. RESULTS: Among the 58 participants, a BN model utilizing discretization and clustering techniques revealed five distinct clusters. Overall, factors associated with breast reconstruction and RT exhibited high discrepancies (24-34 %), while RT-related side effects demonstrated low discrepancies (3-11 %) among the experts. When incorporating recurrence and RT-related side effects, the mean ODB of (y)pN1 patients was 0.258 (range, 0.244-0.337), with a higher tendency observed in triple-negative breast cancer (TNBC) or mastectomy cases. The ODB for TNBC patients undergoing mastectomy without postmastectomy radiotherapy was 0.327, whereas for non-TNBC patients undergoing breast conserving surgery with RT, the disease burden was 0.251. There was an increasing trend in ODB as the field of RT increased. CONCLUSION: We developed a Bayesian network model based on an expert survey, which helps to understand treatment patterns and enables precise estimations of RT-related risk and benefit in (y)pN1 patients.

Developing prompts from large language model for extracting clinical information from pathology and ultrasound reports in breast cancer.

PURPOSE: We aimed to evaluate the time and cost of developing prompts using large language model (LLM), tailored to extract clinical factors in breast cancer patients and their accuracy. MATERIALS AND METHODS: We collected data from reports of surgical pathology and ultrasound from breast cancer patients who underwent radiotherapy from 2020 to 2022. We extracted the information using the Generative Pre-trained Transformer (GPT) for Sheets and Docs extension plugin and termed this the "LLM" method. The time and cost of developing the prompts with LLM methods were assessed and compared with those spent on collecting information with "full manual" and "LLM-assisted manual" methods. To assess accuracy, 340 patients were randomly selected, and the extracted information by LLM method were compared with those collected by "full manual" method. RESULTS: Data from 2,931 patients were collected. We developed 12 prompts for Extract function and 12 for Format function to extract and standardize the information. The overall accuracy was 87.7%. For lymphovascular invasion, it was 98.2%. Developing and processing the prompts took 3.5 hours and 15 minutes, respectively. Utilizing the ChatGPT application programming interface cost US $65.8 and when factoring in the estimated wage, the total cost was US $95.4. In an estimated comparison, "LLM-assisted manual" and "LLM" methods were time- and cost-efficient compared to the "full manual" method. CONCLUSION: Developing and facilitating prompts for LLM to derive clinical factors was efficient to extract crucial information from huge medical records. This study demonstrated the potential of the application of natural language processing using LLM model in breast cancer patients. Prompts from the current study can be re-used for other research to collect clinical information.

Evaluation of the correlation between gaze avoidance and schizophrenia psychopathology with deep learning-based emotional recognition.

OBJECTIVE: To investigate the correlation between gaze avoidance and psychopathology in patients with schizophrenia through eye movement measurements in real-life interpersonal situations. METHODS: We enrolled 52 clinically stable patients with schizophrenia. Psychopathology was evaluated using the Positive and Negative Syndrome Scale (PANSS), Hamilton Depression Rating Scale, and Hamilton Anxiety Rating Scale. After presenting a visual stimulus, eye movements were measured with Tobii Pro Wearable Glasses 2, and deep learning-based emotional recognition using the residual masking network was used for neutral stimulus verification. Statistical analyses were performed using Pearson's correlation and regression analyses. RESULTS: Data of 45 participants with verified stimulus neutrality by deep learning image recognition were used for analysis. The first dwelling time was negatively correlated with the PANSS positive syndrome subscale (p = 0.028), general psychopathology subscale (p = 0.008), total score (p = 0.008), 5-factor positive symptoms (p = 0.035), and 5-factor depression/anxiety symptoms (p = 0.043). The baseline-area of interest (AOI) pupil diameter change was positively correlated with PANSS 5-factor positive symptom scores (p = 0.039). After adjusting for additional variables, the same items had a significant effect on the first dwelling time and baseline-AOI pupil diameter change. CONCLUSIONS: Psychopathology, particularly positive symptoms, was associated with gaze avoidance and pupil diameter in patients with schizophrenia. Evaluating the characteristics of eye movements in patients with schizophrenia will enable better understanding of their symptoms.

Determination of metabolizable energy and amino acid digestibility in various hatchery byproducts for broiler chickens.

The objective of the present experiment was to determine ME concentrations and amino acid (AA) digestibility in various hatchery byproducts (HBPs) for broiler chickens. In experiment 1, a total of forty 60-day-old female broiler chickens were allotted to 1 of 5 dietary treatments with 8 replicates and used to measure ME concentrations in HBPs. The basal diet was prepared to contain corn, soybean meal, corn oil, and other non-energy ingredients. Additional 4 experimental diets were prepared to contain 10% of infertile eggs (IFE), unhatched eggs (UHE), low-grade or dead chicks (LDC), and mixture (MIX; 55% IFE, 10% UHE, 10% LDC, and 25% hatched eggshells). In experiment 2, a total of seven hundred and sixteen 1-day-old mixed-sex broiler chickens (1:1 ratio of males and females) were allotted to 1 of 5 dietary treatments with 7 replicates per treatment and used to determine apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of AA in HBPs. The experimental diets consisted of a nitrogen-free diet and 4 diets containing IFE, UHE, LDC, or MIX as a sole source of AA. Results indicated that AME and AMEn values were greater (P < 0.05) for LDC than for IFE, which had greater (P < 0.05) AME and AMEn values for UHE and MIX. The AID and SID of most AA in LDC were greater (P < 0.05) than those in MIX, whereas IFE and UHE had intermediate AID and SID of those AA as compared to LDC and MIX. Average SID of essential AA in LDC was greater (P < 0.05) than in UHE and MIX, but the average SID of nonessential AA did not differ among 4 HBPs. In conclusion, LDC has the greatest ME concentrations and AA digestibility among 3 individual HBPs (IFE, UHE, and LDC). The mixture of HBPs has the least ME concentrations and AA digestibility in broiler chickens. The ME and AA digestibility of HBPs are likely affected by inclusion amounts of hatched eggshells. However, high concentrations of ME and available AA demonstrate that individual HBPs and their mixture are potential protein ingredients for broiler diets.

Prediction of Lead Intake and Tissue Lead Concentrations in Broiler Chickens Using Feather Lead Concentrations.

The present experiment was conducted to derive equations for predicting daily lead (Pb) intake and tissue Pb concentrations in broiler chickens using feather Pb concentrations. A total of 800 3-day-old broiler chickens were allotted to one of five dietary treatments with 16 replicates, each replicate consisting of 10 birds, in a completely randomized design. Dietary Pb concentrations were set to 0, 50, 100, 200, or 400 mg/kg by adding a lead acetate. The experimental diets were provided ad libitum for 32 days. Results indicated that growth performance and serum measurements were not affected by increasing concentrations of Pb in diets, which represented that the toxic level of dietary Pb may exceed over 400 mg/kg in broiler diets. Increasing concentrations of Pb in diets increased Pb concentrations in the liver (linear and quadratic, P < 0.05), breast (linear, P < 0.01), and feather (linear, P < 0.01). Feather Pb concentrations were greater than Pb concentrations in the liver and breast, indicating that the feather is highly responsive tissue of broiler chickens to various dietary Pb concentrations. Consequently, the equations for predicting daily Pb intake and Pb concentrations in the liver and breast were derived from Pb concentrations in the feather. Resulting equations indicated that feather Pb concentrations in broiler chickens can be used to predict both daily Pb intake and Pb concentrations in the liver and breast.

Dietary β-mannanase decreases cloacal temperature of broiler chickens under hot conditions without affecting growth performance / El consumo de β-mananasa disminuye la temperatura cloacal de pollos de engorde bajo condiciones de calor sin afectar su rendimiento de crecimiento / O consumo de β-mananase diminui a temperatura da cloaca do frango de corte em condições de calor sem afetar seu desempenho do crescimento

Abstract Background: High amounts of nonstarch polysaccharides in the diet may increase the amounts of fermentative materials in the hindgut, leading to an increase in fermentative heat production. Dietary β-mannanase is reported to decrease antinutritional effects of β-mannans, such as the potential increase of body heat; however, its efficacy on broiler chickens raised under hot climatic conditions has not been investigated. Objective: To investigate the effects of dietary β-mannanase on growth performance, cloacal temperature, relative lymphoid organ weight, and blood characteristics of broiler chickens raised under hot climatic conditions. Methods: A total of 1,701 1-day-old Ross 308 broiler chickens were randomly allotted to one of three dietary treatments with nine replicates. A basal diet was prepared and added with β-mannanase at 0.05 or 0.10% inclusion levels. The experiment was conducted for 30 days. Average room temperature was 28.8 ± 1.74 ˚C and average relative humidity (RH) was 76.1 ± 11.49% during the experiment. Results: Growth performance of broiler chickens raised under hot climatic conditions was not affected by β-mannanase inclusion. Cloacal temperature decreased at the end of experiment (linear, p<0.05) with increasing inclusion levels of dietary β-mannanase. Increasing inclusion levels of β-mannanase tended to increase (linear, p=0.076) the relative weight of thymus, but had no effects on the relative weight of spleen and bursa of Fabricius. Blood characteristics were not influenced by dietary β-mannanase. Conclusion: Increasing inclusion levels of β-mannanase decrease cloacal temperature; however, it does not directly influence growth performance nor alleviates the heat stress of broiler chickens raised under hot climatic conditions.

Resumen Antecedentes: Altas cantidades de carbohidratos no almidonosos en la dieta pueden aumentar la cantidad de materiales fermentativos en el intestino posterior, aumentando la producción de calor fermentativo. La β-mananasa dietaria disminuye los efectos antinutricionales de los β-mananos, tales como el potencial incremento de la producción calorica; Sin embargo, no se ha investigado su eficacia en pollos de engorde criados bajo condiciones de calor ambiental. Objetivo: Investigar los efectos de la β-mananasa en la dieta sobre el crecimiento, la temperatura cloacal, el peso relativo de los órganos linfoides y las características sanguíneas de pollos de engorde criados bajo condiciones climáticas calientes. Métodos: Un total de 1.701 pollos de engorde de 1 día de edad (Ross 308) fueron asignados al azar a uno de tres tratamientos dietarios con nueve repeticiones. A una dieta basal se le adicionó β-mananasa en niveles de inclusión de 0,05 o 0,10%. El experimento duró 30 días. La temperatura ambiente durante el experimento fue de 28,8 ± 1,74 ˚C y la humedad relativa de 76,1 ± 11,49%. Resultados: La inclusión de β-mananasa no afecto el rendimiento de los pollos. La temperatura cloacal medida al final del experimento disminuyó (lineal, p<0,05) con niveles de inclusión dietarios crecientes de β-mananasa. Niveles incrementales de β-mananasa tendieron a aumentar (lineal, p=0,076) el peso relativo del timo, pero no hubo efecto sobre el peso del bazo o la bursa de Fabricio. La β-mananasa no influenció las características de la sangre. Conclusión: Niveles incrementales de β-mananasa disminuyen la temperatura cloacal, aunque afectan el crecimiento ni alivian el estrés térmico del pollo de engorde criado bajo condiciones climáticas calientes.

Resumo Antecedentes: Altas quantidades de polissacáridos não amiláceos na dieta podem aumentar as quantidades de materiais fermentativos no intestino posterior, levando a um aumento na produção de calor fermentativo. A β-mananase dietética é relatada para diminuir os efeitos antinutricionais da β-manana, tal como o possível aumento da produção de calor; Entretanto, não tem sido investigada a eficácia de la em frangos de corte criados em condições climáticas quentes. Objetivo: Investigar os efeitos da β-mananase na dieta sobre o desempenho do crescimento, a temperatura cloacal, o peso relativo dos órgãos linfóides e as características de sanguíneas de frangos de corte criados em condições climáticas quentes. Métodos: Um total de 1.701 frangos de corte de um dia de idade (Ross 308) foram distribuídos aleatoriamente em um dos três tratamentos dietéticos com nove repetições. A dieta basal foi preparada e a β-mananase foi adicionada à dieta basal com níveis de inclusão de 0,05 ou 0,10%. O experimento foi conduzido durante 30 dias. A temperatura ambiente média foi de 28,8 temperatura ahumidade relativa (HR) média foi de 76,1 ± 11,49% durante o experimento. Resultados: O desempenho de crescimento dos frangos de corte criados em condições climáticas quentes não foi afetado pelos níveis de inclusão de β-mananase. A temperatura cloacal medida no final do experimento foi diminuída (linear, p<0,05) com níveis crescentes de inclusão de β-mananase na dieta. O aumento dos níveis de inclusão da β-mananase tendeu a aumentar (linear, p=0,076) o peso relativo do timo, mas não teve efeitos sobre o peso relativo do baço e da bursa de Fabricius. As características do sangue não foram influenciadas pela β-mananase dietética. Conclusão: Os níveis crescentes de inclusão de β-mananase diminuem a temperatura cloacal; entretanto, isso não influencia diretamente o desempenho do crescimento e alivia o estresse térmico dos frangos de corte criados em condições climáticas quentes.

Effects of dietary ß-mannanase supplementation on the additivity of true metabolizable energy values for broiler diets.

OBJECTIVE: This experiment was conducted to determine the effects of dietary ß-mannanase on the additivity of true metabolizable energy (TME) and nitrogen-corrected true metabolizable energy (TMEn) for broiler diets. METHODS: A total of 144 21-day-old broilers were randomly allotted to 12 dietary treatments with 6 replicates. Five treatments consisted of 5 ingredients of corn, wheat, soybean meal, corn distillers dried grains with solubles, or corn gluten meal. One mixed diet containing 200 g/kg of those 5 ingredients also was prepared. Additional 6 treatments were prepared by mixing 0.5 g/kg dietary ß-mannanase with those 5 ingredients and the mixed diet. Based on a precision-fed chicken assay, TME and TMEn values for 5 ingredients and the mixed diet as affected by dietary ß-mannanase were determined. RESULTS: Results indicated that when ß-mannanase was not added to the diet, measured TME and TMEn values for the diet did not differ from the predicted values for the diet, which validated the additivity. However, for the diet containing ß-mannanase, measured TMEn value was greater (p<0.05) than predicted TMEn value, indicating that the additivity was not validated. CONCLUSION: In conclusion, the additivity of energy values for the mixed diet may not be guaranteed if the diet contains ß-mannanase.

Effect of dietary ß-mannanase on productive performance, egg quality, and utilization of dietary energy and nutrients in aged laying hens raised under hot climatic conditions.

OBJECTIVE: The objective of this experiment was to investigate the effect of dietary ß-mannanase on productive performance, egg quality, and utilization of dietary energy and nutrients in aged laying hens raised under hot climatic conditions. METHODS: A total of 320 84-wk-old Hy-line Brown aged laying hens were allotted to one of four treatments with eight replicates in a completely randomized design. Two dietary treatments with high energy (HE; 2,800 kcal/kg nitrogen-corrected apparent metabolizable energy [AMEn]) and low energy (LE; 2,700 kcal/kg AMEn) were formulated. Two additional diets were prepared by adding 0.04% (MN4) or 0.08% ß-mannanase (MN8) to LE treatment diets. The feeding trial was conducted for 28 d, covering a period from July to August in South Korea. The average daily room temperature and relative humidity were 29.2°C and 83%, respectively. RESULTS: Productive performance, egg quality, and cloacal temperature were not influenced by dietary treatments. The measured AMEn values for MN8 diets were similar to those for HE diets, which were greater (p<0.05) than those for LE and MN4 diets. However, the AMEn values for MN8 diets did not differ from those for LE and MN4 diets. CONCLUSION: The addition of ß-mannanase to low energy diets increases energy values for diets fed to aged laying hens. However, this increase has little positive impacts on performance and egg quality. These results indicate that dietary ß-mannanase does not mitigate the heat stress of aged laying hens raised under hot climatic conditions.

Effect of dietary net energy concentrations on growth performance and net energy intake of growing gilts.

OBJECTIVE: This experiment investigated the effect of dietary net energy (NE) concentrations on growth performance and NE intake of growing gilts. METHODS: Five diets were formulated to contain 9.6, 10.1, 10.6, 11.1, and 11.6 MJ NE/kg, respectively. A metabolism trial with 10 growing pigs (average body weight [BW] = 15.9±0.24 kg) was conducted to determine NE concentrations of 5 diets based on French and Dutch NE systems in a 5×5 replicated Latin square design. A growth trial also was performed with five dietary treatments and 12 replicates per treatment using 60 growing gilts (average BW = 15.9±0.55 kg) for 28 days. A regression analysis was performed to predict daily NE intake from the BW of growing gilts. RESULTS: Increasing NE concentrations of diets did not influence average daily gain and average daily feed intake of growing gilts. There was a quadratic relationship (p = 0.01) between dietary NE concentrations and feed efficiency (G:F), although the difference in G:F among treatment means was relatively small. Regression analysis revealed that daily NE intake was linearly associated with the BW of growing gilts. The prediction equations for NE intake with the BW of growing gilts were: NE intake (MJ/d) = 1.442+(0.562×BW, kg), R2 = 0.796 when French NE system was used, whereas NE intake (MJ/d) = 1.533+(0.614×BW, kg), R2 = 0.810 when Dutch NE system was used. CONCLUSION: Increasing NE concentrations of diets from 9.6 to 11.6 MJ NE/kg have little impacts on growth performance of growing gilts. Daily NE intake can be predicted from the BW between 15 and 40 kg in growing gilts.

Effect of superdosing phytase on productive performance and egg quality in laying hens.

OBJECTIVE: An experiment was conducted to determine the effect of superdosing phytase on productive performance and egg quality in laying hens. METHODS: A total of 200 42-wk-old Hy-Line Brown laying hens were allotted into 1 of 5 dietary treatments with 5 replicates consisting of 8 hens per replicate. The positive control (PC) and negative control diets (NC) were prepared based on the recommended P levels in layer diets. Supplemental phytase was added to the negative control diet at 10,000 (SD10), 20,000 (SD20), or 30,000 (SD30) fytase units (FTU)/kg. Productive performance was summarized for 6 weeks from 42 weeks to 47 weeks of age. Egg quality was assessed from 4 eggs per replicate randomly collected at the conclusion of the experiment. RESULTS: The SD20 treatment had greater (p<0.05) hen-day egg production than PC, NC, and SD10 treatment groups. There was no difference in hen-day egg production between SD20 and SD30 treatment groups. However, SD30 treatment had greater (p<0.05) hen-day egg production than PC treatment, but showed no difference in hen-day egg production as compared to NC and SD10 treatment groups. However, egg weight, egg mass, feed intake, and feed conversion ratio were not affected by dietary treatments. Egg quality including eggshell strength, eggshell color, egg yolk color, and haugh unit was not influenced by dietary treatments. CONCLUSION: Superdosing level of 20,000 FTU/kg phytase in diets has a positive effect on egg production rate, but no beneficial effect on egg quality in laying hens.

Effect of dietary calcium concentrations in low non-phytate phosphorus diets containing phytase on growth performance, bone mineralization, litter quality, and footpad dermatitis incidence in growing broiler chickens.

OBJECTIVE: An experiment was conducted to investigate the effect of dietary Ca concentrations in low non-phytate phosphorus (NPP) diets containing phytase on growth performance, bone mineralization, litter quality, and footpad dermatitis (FPD) incidence in growing broiler chickens. METHODS: A total of 1,800 21-day-old Ross 308 growing broiler chickens were allotted to 1 of 6 dietary treatments with 6 replicated cages. Six diets were formulated to provide increasing Ca concentrations of 4.0, 5.0, 6.0, 7.0, 8.0, or 9.0 g/kg in diets. The concentrations of NPP in all diets were maintained at 3.0 g/kg, and phytase was supplemented to all diets at the level of 1,000 fytase units (FTU)/kg. At the end of the 14-d feeding trial, birds were euthanized for tibia sampling, and litter samples were collected from 3 areas in the cage. The FPD incidence was measured based on a 6-point scoring system. RESULTS: Dietary Ca concentrations had no effect on growth performance of growing broiler chickens. However, a tendency (linear, p = 0.05) for decreased feed efficiency was observed as dietary Ca concentrations were increased. The concentrations of Ca and P in the tibia of broiler chickens increased (linear and quadratic, p<0.01) with increasing Ca concentrations in low NPP diets containing phytase. Litter pH, moisture, and N contents were not affected by increasing Ca concentrations in low NPP diets containing phytase. However, a tendency (quadratic, p = 0.10) for increased FPD incidence with increasing dietary Ca concentrations was observed. CONCLUSION: Dietary Ca concentrations from 4.0 to 9.0 g/kg in low NPP diets containing phytase have little effects on growth performance of growing broiler chickens. However, Ca and P concentrations in the tibia are decreased if dietary Ca concentrations are less than 5.0 g/kg. The FPD incidence for growing broiler chickens may be decreased if less than 9.0 g/kg of Ca is included in diets.