Incidence, characteristics, and management of central nervous system metastases in patients with inflammatory breast cancer.

BACKGROUND: Patients with inflammatory breast cancer (IBC) have a high risk of central nervous system metastasis (mCNS). The purpose of this study was to quantify the incidence of and identify risk factors for mCNS in patients with IBC. METHODS: The authors retrospectively reviewed patients diagnosed with IBC between 1997 and 2019. mCNS-free survival time was defined as the date from the diagnosis of IBC to the date of diagnosis of mCNS or the date of death, whichever occurred first. A competing risks hazard model was used to evaluate risk factors for mCNS. RESULTS: A total of 531 patients were identified; 372 patients with stage III and 159 patients with de novo stage IV disease. During the study, there were a total of 124 patients who had mCNS. The 1-, 2-, and 5-year incidence of mCNS was 5%, 9%, and 18% in stage III patients (median follow-up: 5.6 years) and 17%, 30%, and 42% in stage IV patients (1.8 years). Multivariate analysis identified triple-negative tumor subtype as a significant risk factor for mCNS for stage III patients. For patients diagnosed with metastatic disease, visceral metastasis as first metastatic site, triple-negative subtype, and younger age at diagnosis of metastases were risk factors for mCNS. CONCLUSIONS: Patients with IBC, particularly those with triple-negative IBC, visceral metastasis, and those at a younger age at diagnosis of metastatic disease, are at significant risk of developing mCNS. Further investigation into prevention of mCNS and whether early detection of mCNS is associated with improved IBC patient outcomes is warranted.

A Grant-Based Experiment to Train Clinical Investigators: The AACR/ASCO Methods in Clinical Cancer Research Workshop.

To address the need for clinical investigators in oncology, American Association for Cancer Research (AACR) and American Society for Clinical Oncology (ASCO) established the Methods in Clinical Cancer Research Workshop (MCCRW). The workshop's objectives were to: (i) provide training in the methods, design, and conduct of clinical trials; (ii) ensure that clinical trials met federal and international ethical guidelines; (iii) evaluate the effectiveness of the workshop; and (iv) create networking opportunities for young investigators with mentoring senior faculty. Educational methods included: (i) didactic lectures, (ii) Small Group Discussion Sessions, (iii) Protocol Development Groups, and (iv) one-on-one mentoring. Learning focused on the development of an Institutional Review Board (IRB)-ready protocol, which was submitted on the last day of the workshop. Evaluation methods included: (i) pre- and postworkshop tests, (ii) students' workshop evaluations, (iii) faculty's ratings of protocol development, (iv) students' productivity in clinical research after the workshop, and (v) an independent assessment of the workshop. From 1996 to 2014, 1,932 students from diverse backgrounds attended the workshop. There was a significant improvement in the students' level of knowledge from the pre- to the postworkshop exams (P < 0.001). Across the classes, student evaluations were very favorable. At the end of the workshop, faculty rated 92% to 100% of the students' protocols as ready for IRB submission. Intermediate and long-term follow-ups indicated that more than 92% of students were actively involved in patient-related research, and 66% had implemented five or more protocols. This NCI-sponsored MCCRW has had a major impact on the training of clinicians in their ability to design and implement clinical trials in cancer research.

Clinical and economic outcomes of treatment sequences for intermediate- to poor-risk advanced renal cell carcinoma.

Aim: To assess the cost-effectiveness of treatment sequences for patients with intermediate- to poor-risk advanced renal cell carcinoma. Patients & methods: A discrete event simulation model was developed to estimate patients' lifetime costs and survival. Efficacy inputs were derived from the CheckMate 214 and CheckMate 025 studies and network meta-analyses. Safety and cost data were obtained from the published literature. Results: The estimated average quality-adjusted life-years (QALYs) gained was the highest on nivolumab + ipilimumab-initiated sequences (3.6-5.3 QALYs) versus tyrosine kinase inhibitor (TKI)-initiated sequences (2.1-3.7 QALYs). Incremental cost per QALY gained for nivolumab + ipilimumab-initiated sequences was below the willingness-to-pay threshold of $150,000 versus other sequences. Conclusion: Immuno-oncology combination therapy followed by TKIs is cost-effective versus TKI sequences followed by immuno-oncology or sequencing TKIs.

Expanded Prostate Cancer Index Composite-26 (EPIC-26) Online: Validation of an Internet-Based Instrument for Assessment of Health-Related Quality of Life After Treatment for Localized Prostate Cancer.

OBJECTIVES: To test the validity of an Internet-based version of Expanded Prostate Cancer Index Composite (EPIC-26) versus the phone-based version. Most men will survive for years after treatment for localized prostate cancer (PCa) and may experience lasting treatment-related toxicities affecting health-related quality of life. The EPIC-26 is a validated instrument that measures health-related quality of life across 5 PCa-specific domains. Previously, EPIC-26 was administered via phone in a large multicenter clinical trial. METHODS: We developed an Internet-based version of EPIC-26. We recruited subjects from two prospective longitudinal study cohorts of PCa patients undergoing local therapy: PROST-QA, and PROSTQA-RP2. Subjects were randomized to either an "Internet-first" or "phone-first" group. Subjects were offered the alternate questionnaire modality 2 weeks after completing the initial modality. RESULTS: 181 subjects were offered enrollment; 133 agreed to participate. 65 subjects were randomized to the "Internet- first" group and 68 subjects to the "phone-first" group. Of these, 37 and 26 subjects respectively completed both questionnaire versions (response rate: 44.4%). Test-retest analysis showed significant intraclass correlations in all 5 domains of EPIC-26: urinary incontinence (r = 0.96), urinary irritation (r = 0.85), bowel function (r = 0.61), sexual function (r = 0.94), and hormonal function (r = 0.89). There was no effect of order of questionnaire administration. CONCLUSION: This study demonstrates excellent correlation of responses between Internet-based and phone-based EPIC-26 administration. All domains demonstrated test-retest reliability between modalities, without ordering effect. This validates the use of internet-based EPIC-26 in international registries as part of the International Consortium for Health Outcomes Measurement effort, and may facilitate its use in clinical practice and quality improvement.

Clinical and economic outcomes associated with treatment sequences in patients with BRAF-mutant advanced melanoma.

AIM: The cost-effectiveness of treatment sequences in BRAF-mutant advanced melanoma. MATERIALS & METHODS: A discrete event simulation model was developed to estimate total costs and health outcomes over a patient's lifetime (30 years). Efficacy was based on the CheckMate 067/069 trials and a matching-adjusted-indirect comparison between immuno-oncology and targeted therapies. Safety, cost (in US dollars; US third-party payer perspective) and health-related quality-of-life inputs were based on published literature. RESULTS: Estimated survival gain was higher for sequences initiating with anti-PD-1 + anti-CTLA-4 than for anti-PD-1 monotherapy or BRAF+MEK inhibitors. The incremental cost-effectiveness ratio per QALY gained for first-line anti-PD-1 + anti-CTLA-4 was US$54,273 versus first-line anti-PD-1 and $79,124 versus first-line BRAF+MEK inhibitors. CONCLUSION: Initiating treatment with anti-PD-1 + anti-CTLA-4 was more cost-effective than initiation with anti-PD-1 monotherapy or BRAF+MEK inhibitors.

Sequential treatment approaches in the management of BRAF wild-type advanced melanoma: a cost-effectiveness analysis.

AIM: To evaluate the cost-effectiveness of treatment sequences with checkpoint inhibitors in patients with BRAF wild-type melanoma. MATERIALS & METHODS: Using a discrete event simulation model, cost and health outcomes were estimated. Pooled data from CheckMate 067/069 trials were used to calculate survival outcomes including treatment-free interval extrapolated over a patient's lifetime. Costs accounted for treatment, administration, toxicity, and disease management. RESULTS: First-line anti-PD-1 + anti-CTLA-4 initiating sequences had the highest estimated mean survival gain (7.6-7.7 years), driven by a longer estimated mean treatment-free interval (5.3 years). Incremental costs per incremental quality-adjusted life year gained for anti-PD-1 + anti-CTLA-4 followed by chemotherapy were US$30,955 versus anti-PD-1 initiating sequences, within the willingness-to-pay threshold. CONCLUSION: Anti-PD-1 + anti-CTLA-4 initiating sequences for BRAF wild-type melanoma are cost-effective versus anti-PD-1.

Association Between Combined TMPRSS2:ERG and PCA3 RNA Urinary Testing and Detection of Aggressive Prostate Cancer.

IMPORTANCE: Potential survival benefits from treating aggressive (Gleason score, ≥7) early-stage prostate cancer are undermined by harms from unnecessary prostate biopsy and overdiagnosis of indolent disease. OBJECTIVE: To evaluate the a priori primary hypothesis that combined measurement of PCA3 and TMPRSS2:ERG (T2:ERG) RNA in the urine after digital rectal examination would improve specificity over measurement of prostate-specific antigen alone for detecting cancer with Gleason score of 7 or higher. As a secondary objective, to evaluate the potential effect of such urine RNA testing on health care costs. DESIGN, SETTING, AND PARTICIPANTS: Prospective, multicenter diagnostic evaluation and validation in academic and community-based ambulatory urology clinics. Participants were a referred sample of men presenting for first-time prostate biopsy without preexisting prostate cancer: 516 eligible participants from among 748 prospective cohort participants in the developmental cohort and 561 eligible participants from 928 in the validation cohort. INTERVENTIONS/EXPOSURES: Urinary PCA3 and T2:ERG RNA measurement before prostate biopsy. MAIN OUTCOMES AND MEASURES: Presence of prostate cancer having Gleason score of 7 or higher on prostate biopsy. Pathology testing was blinded to urine assay results. In the developmental cohort, a multiplex decision algorithm was constructed using urine RNA assays to optimize specificity while maintaining 95% sensitivity for predicting aggressive prostate cancer at initial biopsy. Findings were validated in a separate multicenter cohort via prespecified analysis, blinded per prospective-specimen-collection, retrospective-blinded-evaluation (PRoBE) criteria. Cost effects of the urinary testing strategy were evaluated by modeling observed biopsy results and previously reported treatment outcomes. RESULTS: Among the 516 men in the developmental cohort (mean age, 62 years; range, 33-85 years) combining testing of urinary T2:ERG and PCA3 at thresholds that preserved 95% sensitivity for detecting aggressive prostate cancer improved specificity from 18% to 39%. Among the 561 men in the validation cohort (mean age, 62 years; range, 27-86 years), analysis confirmed improvement in specificity (from 17% to 33%; lower bound of 1-sided 95% CI, 0.73%; prespecified 1-sided P = .04), while high sensitivity (93%) was preserved for aggressive prostate cancer detection. Forty-two percent of unnecessary prostate biopsies would have been averted by using the urine assay results to select men for biopsy. Cost analysis suggested that this urinary testing algorithm to restrict prostate biopsy has greater potential cost-benefit in younger men. CONCLUSIONS AND RELEVANCE: Combined urinary testing for T2:ERG and PCA3 can avert unnecessary biopsy while retaining robust sensitivity for detecting aggressive prostate cancer with consequent potential health care cost savings.

Relief of Urinary Symptom Burden after Primary Prostate Cancer Treatment.

PURPOSE: Harms of prostate cancer treatment on urinary health related quality of life have been thoroughly studied. In this study we evaluated not only the harms but also the potential benefits of prostate cancer treatment in relieving the pretreatment urinary symptom burden. MATERIALS AND METHODS: In American (1,021) and Spanish (539) multicenter prospective cohorts of men with localized prostate cancer we evaluated the effects of radical prostatectomy, external radiotherapy or brachytherapy in relieving pretreatment urinary symptoms and in inducing urinary symptoms de novo, measured by changes in urinary medication use and patient reported urinary bother. RESULTS: Urinary symptom burden improved in 23% and worsened in 28% of subjects after prostate cancer treatment in the American cohort. Urinary medication use rates before treatment and 2 years after treatment were 15% and 6% with radical prostatectomy, 22% and 26% with external radiotherapy, and 19% and 46% with brachytherapy, respectively. Pretreatment urinary medication use (OR 1.4, 95% CI 1.0-2.0, p = 0.04) and pretreatment moderate lower urinary tract symptoms (OR 2.8, 95% CI 2.2-3.6) predicted prostate cancer treatment associated relief of baseline urinary symptom burden. Subjects with pretreatment lower urinary tract symptoms who underwent radical prostatectomy experienced the greatest relief of pretreatment symptoms (OR 4.3, 95% CI 3.0-6.1), despite the development of deleterious de novo urinary incontinence in some men. The magnitude of pretreatment urinary symptom burden and beneficial effect of cancer treatment on those symptoms were verified in the Spanish cohort. CONCLUSIONS: Men with pretreatment lower urinary tract symptoms may experience benefit rather than harm in overall urinary outcome from primary prostate cancer treatment. Practitioners should consider the full spectrum of urinary symptom burden evident before prostate cancer treatment in treatment decisions.

Multinational Prospective Study of Patient-Reported Outcomes After Prostate Radiation Therapy: Detailed Assessment of Rectal Bleeding.

PURPOSE: The new short Expanded Prostate Cancer Index Composite for Clinical Practice (EPIC-CP) patient-reported health-related quality of life (HRQOL) tool has removed the rectal bleeding question from the previous much longer version, EPIC-26. Herein, we assess the impact of losing the dedicated rectal bleeding question in 2 independent prospective multicenter cohorts. METHODS AND MATERIALS: In a prospective multicenter test cohort (n=865), EPIC-26 patient-reported HRQOL data were collected for 2 years after treatment from patients treated with prostate radiation therapy from 2003 to 2011. A second prospective multicenter cohort (n=442) was used for independent validation. A repeated-effects model was used to predict the change from baseline in bowel summary scores from longer EPIC instruments using the change in EPIC-CP bowel summary scores with and without rectal bleeding scores. RESULTS: Two years after radiation therapy, 91% of patients were free of bleeding, and only 2.6% reported bothersome bleeding problems. Correlations between EPIC-26 and EPIC-CP bowel scores were very high (r2=0.90-0.96) and were statistically improved with the addition of rectal bleeding information (r2=0.94-0.98). Considering all patients, only 0.2% of patients in the test cohort and 0.7% in the validation cohort reported bothersome bleeding and had clinically relevant HRQOL changes missed with EPIC-CP. However, of the 2.6% (n=17) of men with bothersome rectal bleeding in the test cohort, EPIC-CP failed to capture 1 patient (6%) as experiencing meaningful declines in bowel HRQOL. CONCLUSIONS: Modern prostate radiation therapy results in exceptionally low rates of bothersome rectal bleeding, and <1% of patients experience bothersome bleeding and are not captured by EPIC-CP as having meaningful HRQOL declines after radiation therapy. However, in the small subset of patients with bothersome rectal bleeding, the longer EPIC-26 should strongly be considered, given its superior performance in this patient subset.

The Development of Intermediate Clinical Endpoints in Cancer of the Prostate (ICECaP).

New systemic therapies have prolonged the lives of men with metastatic castration-resistant prostate cancer (mCRPC). Use of these therapies in the adjuvant setting when the disease may be micrometastatic and potentially more sensitive to therapies may decrease mortality from prostate cancer. However, the conduct of adjuvant prostate cancer clinical trials is hampered by taking longer than a decade to reach the meaningful endpoint of overall survival (OS) and the fact that many men never die from prostate cancer, even if they relapse. A validated intermediate clinical endpoint (ICE) in prostate cancer that is a robust surrogate for OS has yet to be defined. This paper details the plans, process, and progress of the international Intermediate Clinical Endpoints in Cancer of the Prostate (ICECaP) working group to pool individual patient data from all available clinical trials of radiation or prostatectomy for localized disease and conduct the requisite analyses to determine whether an ICE can be identified. This paper further details the challenges and the a priori statistical analytical plans and strategies to define an ICE for adjuvant prostate cancer clinical trials. In addition, a brief review of the health economic analyses to model the benefits to patients, society and manufacturers is detailed. If successful, the results from this work will provide a robust surrogate for OS that will expedite the design and conduct of future adjuvant therapy trials using new agents that have proven activity in mCRPC. Moreover, it will also define the health economic benefits to patients and societies.

Assessment of Ki67 in breast cancer: recommendations from the International Ki67 in Breast Cancer working group.

Uncontrolled proliferation is a hallmark of cancer. In breast cancer, immunohistochemical assessment of the proportion of cells staining for the nuclear antigen Ki67 has become the most widely used method for comparing proliferation between tumor samples. Potential uses include prognosis, prediction of relative responsiveness or resistance to chemotherapy or endocrine therapy, estimation of residual risk in patients on standard therapy and as a dynamic biomarker of treatment efficacy in samples taken before, during, and after neoadjuvant therapy, particularly neoadjuvant endocrine therapy. Increasingly, Ki67 is measured in these scenarios for clinical research, including as a primary efficacy endpoint for clinical trials, and sometimes for clinical management. At present, the enormous variation in analytical practice markedly limits the value of Ki67 in each of these contexts. On March 12, 2010, an international panel of investigators with substantial expertise in the assessment of Ki67 and in the development of biomarker guidelines was convened in London by the co-chairs of the Breast International Group and North American Breast Cancer Group Biomarker Working Party to consider evidence for potential applications. Comprehensive recommendations on preanalytical and analytical assessment, and interpretation and scoring of Ki67 were formulated based on current evidence. These recommendations are geared toward achieving a harmonized methodology, create greater between-laboratory and between-study comparability, and allow earlier valid applications of this marker in clinical practice.

Assessment of letrozole and tamoxifen alone and in sequence for postmenopausal women with steroid hormone receptor-positive breast cancer: the BIG 1-98 randomised clinical trial at 8·1 years median follow-up.

BACKGROUND: Postmenopausal women with hormone receptor-positive early breast cancer have persistent, long-term risk of breast-cancer recurrence and death. Therefore, trials assessing endocrine therapies for this patient population need extended follow-up. We present an update of efficacy outcomes in the Breast International Group (BIG) 1-98 study at 8·1 years median follow-up. METHODS: BIG 1-98 is a randomised, phase 3, double-blind trial of postmenopausal women with hormone receptor-positive early breast cancer that compares 5 years of tamoxifen or letrozole monotherapy, or sequential treatment with 2 years of one of these drugs followed by 3 years of the other. Randomisation was done with permuted blocks, and stratified according to the two-arm or four-arm randomisation option, participating institution, and chemotherapy use. Patients, investigators, data managers, and medical reviewers were masked. The primary efficacy endpoint was disease-free survival (events were invasive breast cancer relapse, second primaries [contralateral breast and non-breast], or death without previous cancer event). Secondary endpoints were overall survival, distant recurrence-free interval (DRFI), and breast cancer-free interval (BCFI). The monotherapy comparison included patients randomly assigned to tamoxifen or letrozole for 5 years. In 2005, after a significant disease-free survival benefit was reported for letrozole as compared with tamoxifen, a protocol amendment facilitated the crossover to letrozole of patients who were still receiving tamoxifen alone; Cox models and Kaplan-Meier estimates with inverse probability of censoring weighting (IPCW) are used to account for selective crossover to letrozole of patients (n=619) in the tamoxifen arm. Comparison of sequential treatments to letrozole monotherapy included patients enrolled and randomly assigned to letrozole for 5 years, letrozole for 2 years followed by tamoxifen for 3 years, or tamoxifen for 2 years followed by letrozole for 3 years. Treatment has ended for all patients and detailed safety results for adverse events that occurred during the 5 years of treatment have been reported elsewhere. Follow-up is continuing for those enrolled in the four-arm option. BIG 1-98 is registered at clinicaltrials.govNCT00004205. FINDINGS: 8010 patients were included in the trial, with a median follow-up of 8·1 years (range 0-12·4). 2459 were randomly assigned to monotherapy with tamoxifen for 5 years and 2463 to monotherapy with letrozole for 5 years. In the four-arm option of the trial, 1546 were randomly assigned to letrozole for 5 years, 1548 to tamoxifen for 5 years, 1540 to letrozole for 2 years followed by tamoxifen for 3 years, and 1548 to tamoxifen for 2 years followed by letrozole for 3 years. At a median follow-up of 8·7 years from randomisation (range 0-12·4), letrozole monotherapy was significantly better than tamoxifen, whether by IPCW or intention-to-treat analysis (IPCW disease-free survival HR 0·82 [95% CI 0·74-0·92], overall survival HR 0·79 [0·69-0·90], DRFI HR 0·79 [0·68-0·92], BCFI HR 0·80 [0·70-0·92]; intention-to-treat disease-free survival HR 0·86 [0·78-0·96], overall survival HR 0·87 [0·77-0·999], DRFI HR 0·86 [0·74-0·998], BCFI HR 0·86 [0·76-0·98]). At a median follow-up of 8·0 years from randomisation (range 0-11·2) for the comparison of the sequential groups with letrozole monotherapy, there were no statistically significant differences in any of the four endpoints for either sequence. 8-year intention-to-treat estimates (each with SE ≤1·1%) for letrozole monotherapy, letrozole followed by tamoxifen, and tamoxifen followed by letrozole were 78·6%, 77·8%, 77·3% for disease-free survival; 87·5%, 87·7%, 85·9% for overall survival; 89·9%, 88·7%, 88·1% for DRFI; and 86·1%, 85·3%, 84·3% for BCFI. INTERPRETATION: For postmenopausal women with endocrine-responsive early breast cancer, a reduction in breast cancer recurrence and mortality is obtained by letrozole monotherapy when compared with tamoxifen montherapy. Sequential treatments involving tamoxifen and letrozole do not improve outcome compared with letrozole monotherapy, but might be useful strategies when considering an individual patient's risk of recurrence and treatment tolerability. FUNDING: Novartis, United States National Cancer Institute, International Breast Cancer Study Group.

A randomized clinical trial to evaluate optimal treatment for unexplained infertility: the fast track and standard treatment (FASTT) trial.

OBJECTIVE: To determine the value of gonadotropin/intrauterine insemination (FSH/IUI) therapy for infertile women aged 21-39 years. DESIGN: Randomized controlled trial. SETTING: Academic medical center associated with a private infertility center. PATIENT(S): Couples with unexplained infertility. INTERVENTION(S): Couples were randomized to receive either conventional treatment (n=247) with three cycles of clomiphene citrate (CC)/IUI, three cycles of FSH/IUI, and up to six cycles of IVF or an accelerated treatment (n=256) that omitted the three cycles of FSH/IUI. MAIN OUTCOME MEASURE(S): The time it took to establish a pregnancy that led to a live birth and cost-effectiveness, defined as the ratio of the sum of all health insurance charges between randomization and delivery divided by the number of couples delivering at least one live-born baby. RESULT(S): An increased rate of pregnancy was observed in the accelerated arm (hazard ratio [HR], 1.25; 95% confidence interval [CI], 1.00-1.56) compared with the conventional arm. Median time to pregnancy was 8 and 11 months in the accelerated and conventional arms, respectively. Per cycle pregnancy rates for CC/IUI, FSH/IUI, and IVF were 7.6%, 9.8%, and 30.7%, respectively. Average charges per delivery were $9,800 lower (95% CI, $25,100 lower to $3,900 higher) in the accelerated arm compared to conventional treatment. The observed incremental difference was a savings of $2,624 per couple for accelerated treatment and 0.06 more deliveries. CONCLUSION(S): A randomized clinical trial demonstrated that FSH/IUI treatment was of no added value.

Lysine requirements of chronically undernourished adult Indian men, measured by a 24-h indicator amino acid oxidation and balance technique.

BACKGROUND: In earlier studies with well-nourished subjects that used a 24-h indicator amino acid oxidation or balance approach, we concluded that the 1985 FAO/WHO/UNU requirement for lysine (12 mg x kg(-1) x d(-1)) was inadequate for healthy South Asian subjects and proposed a tentative requirement of 30 mg x kg(-1) x d(-1). OBJECTIVE: We assessed whether chronic undernutrition, with low habitual dietary protein and lysine intakes, leads to changed lysine requirements. DESIGN: Twenty-seven otherwise clinically healthy, chronically undernourished Indian men were studied during 2 randomly assigned 7-d diet periods supplying 12 and 30, 18 and 36, or 24 and 42 mg lysine x kg(-1) x d(-1), based on an L-amino acid diet. The subjects' leucine intake was 40 mg x kg(-1) x d(-1). At 1800 on day 6, a 24-h intravenous [(13)C]leucine tracer-infusion protocol was conducted to assess leucine oxidation and daily leucine balance at each test lysine intake. RESULTS: A breakpoint was not identified in the lysine intake-leucine oxidation or balance response over the range of intakes studied. Mixed-models linear regression analysis indicated a mean requirement of 44 mg lysine x kg(-1) x d(-1) (95% CI: 36, 63) for the lysine intake-leucine balance relation. CONCLUSIONS: The mean lysine requirement in chronically undernourished men is estimated to be higher than the value of 30 mg x kg(-1) x d(-1) proposed for well-nourished individuals. This may be related to body-composition differences. It also suggests that these subjects have not elicited a metabolic adaptation in response to their habitually low lysine intakes by substantially improving their efficiency of dietary lysine utilization.