PRO-CTCAE reveals under-recognition of dermatologic symptom burden in hospitalized cancer patients

PURPOSE

Dermatologic adverse events (dAEs) occur frequently in hospitalized patients and can significantly reduce quality of life. Physicians grade dAEs using the Common Terminology Criteria of Adverse Events (CTCAE). However, they often underestimate symptom frequency and severity. The patient-reported outcomes (PRO) version of the CTCAE (PRO-CTCAE) was developed to assess symptoms from the patient's perspective. In this study, we assessed the patient-reported burden of dAEs via the PRO-CTCAE questionnaire and compared results with dAE assessment by treating oncologists and dermatologists.

METHODS

Patients admitted to Memorial Sloan Kettering Cancer Center from 6/1/2018 to 4/30/2019 and received a dermatology consultation were eligible. Once enrolled, participants completed a PRO-CTCAE questionnaire on 14 dermatologic symptoms. CTCAE grades assigned by oncology and dermatology were obtained from clinical notes, and kappa statistics were calculated to evaluate the level of agreement between physician and patient evaluations.

RESULTS

A total of 100 patients (mean age 59.4, 55% male) were prospectively enrolled. The most common patient-reported dAEs were rash (72%), swelling (67%), pruritus (64%), bruising (53%), and hives (37%). Oncologists and dermatologists underreported dAEs except for rash (median kappa values 0.3 [0.02-0.84] and 0.32 [0.02-0.87], respectively). Oncologists and dermatologists were concordant with each other's documented assessment of dAEs (median kappa value 0.985 [0.55-1]).

CONCLUSION

Oncology patient-reported dAEs in a tertiary academic oncologic referral center were under-recognized by providers. PRO-CTCAE may be a useful tool to optimize inpatient dermatologic care for cancer patients by detecting and allowing management of patient-reported dAEs.

Laser therapy as a treatment for chronic radiation fibrosis

BACKGROUND

Chronic radiation fibrosis (CRF) is a long-term sequala of radiation therapy that has a significant impact on patient quality of life. There is no standard of care or single therapeutic modality that has been found to be consistently effective.

OBJECTIVE

To describe our experience using fractional 10,600 nm carbon dioxide (CO₂ ) laser therapy and vascular laser therapy in a series of patients with CRF.

METHODS

Patients presenting to the dermatology service for CRF were evaluated for laser therapy eligibility. Patients were eligible if they had a clinical diagnosis of CRF confirmed by physical examination.

RESULTS

We identified five patients with CRF treated with fractional ablative CO₂ laser and vascular laser. Patients were a median age of 57 years old, and the amount of time between the initiation of radiotherapy and laser treatment ranged between 3 months and 40 years. The satisfactory response was achieved in all cases.

LIMITATIONS

Lack of standardized laser protocol, small sample size, lack of a control group, different anatomical locations CONCLUSION: Fractional ablative and vascular laser therapy may serve as an additional treatment for CRF, leading to functional improvements.

Adjuvant nivolumab plus ipilimumab or nivolumab alone versus placebo in patients with resected stage IV melanoma with no evidence of disease (IMMUNED): final results of a randomised, double-blind, phase 2 trial

BACKGROUND

The IMMUNED trial previously showed significant improvements in recurrence-free survival for adjuvant nivolumab plus ipilimumab as well as for adjuvant nivolumab alone in patients with stage IV melanoma with no evidence of disease after resection or radiotherapy. Here, we report the final analysis, including overall survival data.

METHODS

IMMUNED was an investigator-sponsored, double-blind, placebo-controlled, three-arm, phase 2 trial conducted in 20 academic medical centres in Germany. Eligible patients were aged 18-80 years with stage IV melanoma with no evidence of disease after surgery or radiotherapy. Patients were randomly assigned (1:1:1) to either nivolumab plus ipilimumab (nivolumab 1 mg/kg plus ipilimumab 3 mg/kg every 3 weeks for four doses followed by nivolumab 3 mg/kg every 2 weeks), nivolumab monotherapy (nivolumab 3 mg/kg every 2 weeks), or matching placebo, for up to 1 year. The primary endpoint was recurrence-free survival in the intention-to-treat population. Secondary endpoints were time-to-recurrence, overall survival, progression-free survival or recurrence-free survival 2 (in patients in the placebo group who crossed over to nivolumab monotherapy after experiencing disease recurrence), and safety endpoints. This trial is registered on ClinicalTrials.gov (NCT02523313), and is complete.

FINDINGS

Between Sept 2, 2015, and Nov 20, 2018, 175 patients were enrolled in the study, and 167 were randomly assigned to receive either nivolumab plus ipilimumab (n=56), nivolumab plus ipilimumab-matching placebo (n=59), or double placebo control (n=52). At a median follow-up of 49·2 months (IQR 34·9-58·1), 4-year recurrence-free survival was 64·2% (95% CI 49·2-75·9) in the nivolumab plus ipilimumab group, 31·4% (19·7-43·8) in the nivolumab alone group, and 15·0% (6·7-26·6) in the placebo group. The hazard ratio (HR) for recurrence for the nivolumab plus ipilimumab group versus placebo was 0·25 (97·5% CI 0·13-0·48; p<0·0001), and for the nivolumab group versus placebo was 0·60 (0·36-1·00; p=0·024). Median overall survival was not reached in any treatment group. The HR for overall survival was significantly in favour of the nivolumab plus ipilimumab group versus placebo (HR 0·41; 95% CI 0·17-0·99; p=0·040), but not for the nivolumab group versus placebo (HR 0·75; 0·36-1·56; p=0·44). 4-year overall survival was 83·8% (95% CI 68·8-91·9) in the nivolumab plus ipilimumab group, 72·6% (57·4-83·2) in the nivolumab alone group, and 63·1% (46·9-75·6) in the placebo group. The median progression-free survival or recurrence-free survival 2 of patients in the placebo group who crossed over to nivolumab monotherapy after experiencing disease recurrence was not reached (95% CI 21·2 months to not reached). Rates of grade 3-4 treatment-related adverse events remained largely unchanged compared with our previous report, occurring in 71% (95% CI 57-82) of the nivolumab plus ipilimumab group, and 29% (95% CI 17-42) of patients receiving nivolumab alone. There were no treatment-related deaths.

INTERPRETATION

Both active regimens continued to show significantly improved recurrence-free survival compared with placebo in patients with stage IV melanoma with no evidence of disease who were at high risk of recurrence. Overall survival was significantly improved for patients receiving nivolumab plus ipilimumab compared with placebo. Use of subsequent anti-PD-1-based therapy was high in patients in the placebo group after recurrence and most likely impacted the overall survival comparison of nivolumab alone versus placebo. The recurrence-free and overall survival benefit of nivolumab plus ipilimumab over placebo reinforces the change of practice already initiated for the treatment of patients with stage IV melanoma with no evidence of disease.

FUNDING

Bristol-Myers Squibb.

Evaluation of radio-immunotherapy sequence on immunological responses and clinical outcomes in patients with melanoma brain metastases (ELEKTRA)

In patients with melanoma brain metastases (MBM), a combination of radiotherapy (RT) with immune checkpoint inhibitors (ICI) is routinely used. However, the best sequence of radio-immunotherapy (RIT) remains unclear. In an exploratory phase 2 trial, MBM patients received RT (stereotactic or whole-brain radiotherapy depending on the number of MBM) combined with ipilimumab (ipi) ± nivolumab (nivo) in different sequencing (Rad-ICI or ICI-Rad). Comparators arms included patients treated with ipi-free systemic treatment or without RT (in MBM-free patients). The primary endpoints were radiological and immunological responses in the peripheral blood. Secondary endpoints were progression-free survival (PFS) and overall survival (OS). Of 106 screened, 92 patients were included in the study. Multivariate analysis revealed an advantage for patients starting with RT (Rad-ICI) for overall response rate (RR: p = .007; HR: 7.88 (95%CI: 1.76–35.27)) and disease control rate (DCR: p = .036; HR: 6.26 (95%CI: 1.13–34.71)) with a trend for a better PFS (p = .162; HR: 1.64 (95%CI: 0.8–3.3)). After RT plus two cycles of ipi-based ICI in both RIT sequences, increased frequencies of activated CD4, CD8 T cells and an increase in melanoma-specific T cell responses were observed in the peripheral blood. Lasso regression analysis revealed a significant clinical benefit for patients treated with Rad-ICI sequence and immunological features, including high frequencies of memory T cells and activated CD8 T cells in the blood. This study supports increasing evidence that sequencing RT followed by ICI treatment may have better effects on the immunological responses and clinical outcomes in MBM patients.

Efficacy of laser CO2 treatment for refractory lymphedema secondary to cancer treatments

Lymphedema is a frequent debilitating condition among cancer patients. Daily supportive treatment may be necessary without long-term improvement. We describe two cases with chronic refractory lymphedema treated with fractional 10,600 nm CO₂ laser. A 61-year-old female with locally advanced cervical cancer presented with postsurgical edematous swelling of the vulva and mons pubis and recurring cellulitis due to chronic lymphangiectasia. After six treatments of fractional CO₂ laser, she noticed an 80% reduction of lymphorrea, swelling, and frequency of cellulitis. A 32-year old melanoma patient presented with refractory right lower leg lymphedema post right inguinal lymph node dissection and radiation. After fractional CO₂ laser, she noted increased softness of her inguinal scar and a decrease of the lower leg edema. Fractional CO₂ laser may be useful in addressing chronic refractory lymphedema. Further research should confirm our findings to consider fractional laser as a standard method in the treatment of chronic lymphedema.

Adjuvant nivolumab plus ipilimumab or nivolumab monotherapy versus placebo in patients with resected stage IV melanoma with no evidence of disease (IMMUNED): a randomised, double-blind, placebo-controlled, phase 2 trial

BACKGROUND

Nivolumab and ipilimumab, alone or in combination, are widely used immunotherapeutic treatment options for patients with advanced-ie, unresectable or metastatic-melanoma. This criterion, however, excludes patients with stage IV melanoma with no evidence of disease. We therefore aimed to evaluate the safety and efficacy of adjuvant nivolumab plus ipilimumab or nivolumab monotherapy versus a placebo in this patient population.

METHODS

We did a randomised, double-blind, placebo-controlled, phase 2 trial in 20 German academic medical centres. Eligible patients were aged 18-80 years with stage IV melanoma with no evidence of disease after surgery or radiotherapy. Key exclusion criteria included uveal or mucosal melanoma, previous therapy with checkpoint inhibitors, and any previous immunosuppressive therapy within the 30 days before study drug administration. Eligible patients were randomly assigned (1:1:1), using a central, interactive, online system, to the nivolumab plus ipilimumab group (1 mg/kg of intravenous nivolumab every 3 weeks plus 3 mg/kg of intravenous ipilimumab every 3 weeks for four doses, followed by 3 mg/kg of nivolumab every 2 weeks), nivolumab monotherapy group (3 mg/kg of intravenous nivolumab every 2 weeks plus ipilimumab-matching placebo during weeks 1-12), or double-matching placebo group. The primary endpoint was the recurrence-free survival in the intention-to-treat population. The results presented in this report reflect the prespecified interim analysis of recurrence-free survival after 90 events had been reported. This study is registered with ClinicalTrials.gov, NCT02523313, and is ongoing.

FINDINGS

Between Sept 2, 2015, and Nov 20, 2018, 167 patients were randomly assigned to receive nivolumab plus ipilimumab (n=56), nivolumab (n=59), or placebo (n=52). As of July 2, 2019, at a median follow-up of 28·4 months (IQR 17·7-36·8), median recurrence-free survival was not reached in the nivolumab plus ipilimumab group, whereas median recurrence-free survival was 12·4 months (95% CI 5·3-33·3) in the nivolumab group and 6·4 months (3·3-9·6) in the placebo group. The hazard ratio for recurrence for the nivolumab plus ipilimumab group versus placebo group was 0·23 (97·5% CI 0·12-0·45; p<0·0001), and for the nivolumab group versus placebo group was 0·56 (0·33-0·94; p=0·011). In the nivolumab plus ipilimumab group, recurrence-free survival at 1 year was 75% (95% CI 61·0-84·9) and at 2 years was 70% (55·1-81·0); in the nivolumab group, 1-year recurrence-free survival was 52% (38·1-63·9) and at 2 years was 42% (28·6-54·5); and in the placebo group, this rate was 32% (19·8-45·3) at 1 year and 14% (5·9-25·7) at 2 years. Treatment-related grade 3-4 adverse events were reported in 71% (95% CI 57-82) of patients in the nivolumab plus ipilimumab group and in 27% (16-40) of those in the nivolumab group. Treatment-related adverse events of any grade led to treatment discontinuation in 34 (62%) of 55 patients in the nivolumab plus ipilimumab group and seven (13%) of 56 in the nivolumab group. Three deaths from adverse events were reported but were considered unrelated to the study treatment.

INTERPRETATION

Adjuvant therapy with nivolumab alone or in combination with ipilimumab increased recurrence-free survival significantly compared with placebo in patients with stage IV melanoma with no evidence of disease. The rates of grade 3-4 treatment-related adverse events in both active treatment groups were higher than the rates reported in previous pivotal trials done in advanced melanoma with measurable disease.

FUNDING

Bristol-Myers Squibb.

Targeted Therapy in Advanced Melanoma With Rare BRAF Mutations

PURPOSE

BRAF/MEK inhibition is a standard of care for patients with BRAF V600E/K-mutated metastatic melanoma. For patients with less frequent BRAF mutations, however, efficacy data are limited.

METHODS

In the current study, 103 patients with metastatic melanoma with rare, activating non-V600E/K BRAF mutations that were treated with either a BRAF inhibitor (BRAFi), MEK inhibitor (MEKi), or the combination were included. BRAF mutation, patient and disease characteristics, response, and survival data were analyzed.

RESULTS

Fifty-eight patient tumors (56%) harbored a non-E/K V600 mutation, 38 (37%) a non-V600 mutation, and seven had both V600E and a rare BRAF mutation (7%). The most frequent mutations were V600R (43%; 44 of 103), L597P/Q/R/S (15%; 15 of 103), and K601E (11%; 11 of 103). Most patients had stage IV disease and 42% had elevated lactate dehydrogenase at BRAFi/MEKi initiation. Most patients received combined BRAFi/MEKi (58%) or BRAFi monotherapy (37%). Of the 58 patients with V600 mutations, overall response rate to BRAFi monotherapy and combination BRAFi/MEKi was 27% (six of 22) and 56% (20 of 36), respectively, whereas median progression-free survival (PFS) was 3.7 months and 8.0 months, respectively (P = .002). Of the 38 patients with non-V600 mutations, overall response rate was 0% (zero of 15) to BRAFi, 40% (two of five) to MEKi, and 28% (five of 18) to combination treatment, with a median PFS of 1.8 months versus 3.7 months versus 3.3 months, respectively. Multivariable analyses revealed superior survival (PFS and overall survival) with combination over monotherapy in rare V600 and non-V600 mutated melanoma.

CONCLUSION

Patients with rare BRAF mutations can respond to targeted therapy, however, efficacy seems to be lower compared with V600E mutated melanoma. Combination BRAFi/MEKi seems to be the best regimen for both V600 and non-V600 mutations. Yet interpretation should be done with care because of the heterogeneity of patients with small sample sizes for some of the reported mutations.

Physicians' level of hindrance by body hair in dermatoscopy and clinical benefit of an automated hair removal algorithm

BACKGROUND AND OBJECTIVES

Dermatoscopy may be hindered by body hair, and the development of an automated hair removal algorithm (AuHRA) might improve the diagnostic accuracy. However, the physicians' exact level of hindrance and the clinical benefit attained by AuHRA has not been assessed. The objectives of this study are to quantify the physicians' level of hindrance by body hair and the level of improvement in the visibility of underlying dermatoscopic patterns after application of AuHRA to digital images of hair-covered nevi.

PATIENTS AND METHODS

A cross-sectional reader study including 59 sets of dermatoscopic images of benign nevi that were presented to six dermatologists. Each set included three images of one individual nevus (unshaved/physically shaved/digitally shaved with AuHRA), which were compared to each other within each set to assess the level of improvement caused by hair removal.

RESULTS

In comparison to unshaved lesions, dermatologists attributed the highest mean level of improvement to a physical shave (+1.36, p < 0.001) followed by AuHRA's digital shave (+0.79, p < 0.001). The majority of dermatologists considered the application of AuHRA as helpful and confirmed a medical need.

CONCLUSIONS

The dermatologists in our study confirmed a substantial impairment of the dermatoscopic examination by body hair. We demonstrated a clinical benefit attained by AuHRA in comparison to unshaved or physically shaved lesions.

Fatal Toxic Effects Associated With Immune Checkpoint Inhibitors: A Systematic Review and Meta-analysis

Importance

Immune checkpoint inhibitors (ICIs) are now a mainstay of cancer treatment. Although rare, fulminant and fatal toxic effects may complicate these otherwise transformative therapies; characterizing these events requires integration of global data.

Objective

To determine the spectrum, timing, and clinical features of fatal ICI-associated toxic effects.

Design, Setting, and Participants

We retrospectively queried a World Health Organization (WHO) pharmacovigilance database (Vigilyze) comprising more than 16 000 000 adverse drug reactions, and records from 7 academic centers. We performed a meta-analysis of published trials of anti-programmed death-1/ligand-1 (PD-1/PD-L1) and anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) to evaluate their incidence using data from large academic medical centers, global WHO pharmacovigilance data, and all published ICI clinical trials of patients with cancer treated with ICIs internationally.

Exposures

Anti-CTLA-4 (ipilimumab or tremelimumab), anti-PD-1 (nivolumab, pembrolizumab), or anti-PD-L1 (atezolizumab, avelumab, durvalumab).

Main Outcomes and Measures

Timing, spectrum, outcomes, and incidence of ICI-associated toxic effects.

Results

Internationally, 613 fatal ICI toxic events were reported from 2009 through January 2018 in Vigilyze. The spectrum differed widely between regimens: in a total of 193 anti-CTLA-4 deaths, most were usually from colitis (135 [70%]), whereas anti-PD-1/PD-L1-related fatalities were often from pneumonitis (333 [35%]), hepatitis (115 [22%]), and neurotoxic effects (50 [15%]). Combination PD-1/CTLA-4 deaths were frequently from colitis (32 [37%]) and myocarditis (22 [25%]). Fatal toxic effects typically occurred early after therapy initiation for combination therapy, anti-PD-1, and ipilimumab monotherapy (median 14.5, 40, and 40 days, respectively). Myocarditis had the highest fatality rate (52 [39.7%] of 131 reported cases), whereas endocrine events and colitis had only 2% to 5% reported fatalities; 10% to 17% of other organ-system toxic effects reported had fatal outcomes. Retrospective review of 3545 patients treated with ICIs from 7 academic centers revealed 0.6% fatality rates; cardiac and neurologic events were especially prominent (43%). Median time from symptom onset to death was 32 days. A meta-analysis of 112 trials involving 19 217 patients showed toxicity-related fatality rates of 0.36% (anti-PD-1), 0.38% (anti-PD-L1), 1.08% (anti-CTLA-4), and 1.23% (PD-1/PD-L1 plus CTLA-4).

Conclusions and Relevance

In the largest evaluation of fatal ICI-associated toxic effects published to date to our knowledge, we observed early onset of death with varied causes and frequencies depending on therapeutic regimen. Clinicians across disciplines should be aware of these uncommon lethal complications.

Fatal Toxic Effects Associated With Immune Checkpoint Inhibitors: A Systematic Review and Meta-analysis

IMPORTANCE

Immune checkpoint inhibitors (ICIs) are now a mainstay of cancer treatment. Although rare, fulminant and fatal toxic effects may complicate these otherwise transformative therapies; characterizing these events requires integration of global data.

OBJECTIVE

To determine the spectrum, timing, and clinical features of fatal ICI-associated toxic effects.

DESIGN, SETTING, AND PARTICIPANTS

We retrospectively queried a World Health Organization (WHO) pharmacovigilance database (Vigilyze) comprising more than 16 000 000 adverse drug reactions, and records from 7 academic centers. We performed a meta-analysis of published trials of anti-programmed death-1/ligand-1 (PD-1/PD-L1) and anti-cytotoxic T lymphocyte antigen-4 (CTLA-4) to evaluate their incidence using data from large academic medical centers, global WHO pharmacovigilance data, and all published ICI clinical trials of patients with cancer treated with ICIs internationally.

EXPOSURES

Anti-CTLA-4 (ipilimumab or tremelimumab), anti-PD-1 (nivolumab, pembrolizumab), or anti-PD-L1 (atezolizumab, avelumab, durvalumab).

MAIN OUTCOMES AND MEASURES

Timing, spectrum, outcomes, and incidence of ICI-associated toxic effects.

RESULTS

Internationally, 613 fatal ICI toxic events were reported from 2009 through January 2018 in Vigilyze. The spectrum differed widely between regimens: in a total of 193 anti-CTLA-4 deaths, most were usually from colitis (135 [70%]), whereas anti-PD-1/PD-L1-related fatalities were often from pneumonitis (333 [35%]), hepatitis (115 [22%]), and neurotoxic effects (50 [15%]). Combination PD-1/CTLA-4 deaths were frequently from colitis (32 [37%]) and myocarditis (22 [25%]). Fatal toxic effects typically occurred early after therapy initiation for combination therapy, anti-PD-1, and ipilimumab monotherapy (median 14.5, 40, and 40 days, respectively). Myocarditis had the highest fatality rate (52 [39.7%] of 131 reported cases), whereas endocrine events and colitis had only 2% to 5% reported fatalities; 10% to 17% of other organ-system toxic effects reported had fatal outcomes. Retrospective review of 3545 patients treated with ICIs from 7 academic centers revealed 0.6% fatality rates; cardiac and neurologic events were especially prominent (43%). Median time from symptom onset to death was 32 days. A meta-analysis of 112 trials involving 19 217 patients showed toxicity-related fatality rates of 0.36% (anti-PD-1), 0.38% (anti-PD-L1), 1.08% (anti-CTLA-4), and 1.23% (PD-1/PD-L1 plus CTLA-4).

CONCLUSIONS AND RELEVANCE

In the largest evaluation of fatal ICI-associated toxic effects published to date to our knowledge, we observed early onset of death with varied causes and frequencies depending on therapeutic regimen. Clinicians across disciplines should be aware of these uncommon lethal complications.

Mechano-insensitive nociceptors are sufficient to induce histamine-induced itch

The nerve fibres underlying histamine-induced itch have not been fully elucidated. We blocked the lateral femoral cutaneous nerve and mapped the skin area unresponsive to mechanical stimulation, but still sensitive to electrically induced pain. Nerve block induced significantly larger anaesthetic areas to mechanical (100 mN pin-prick, 402 ± 61 cm²; brush, 393 ± 63 cm²) and heat pain stimuli (401 ± 53 cm²) compared with electrical stimulation (352 ± 62 cm², p < 0.05), whereas the anaesthetic area tested with 260 mN (374 ± 57 cm²) did not differ significantly. Histamine was applied by iontophoresis (7.5 mC) at skin sites in which mechanical sensitivity was blocked, but electrical stimulation was still perceived 30 min after the nerve block (n = 9). In these areas iontophoresis of histamine provoked itching in 8/9 subjects with a mean maximum of 4.6 ± 1 (on an 11-point rating scale). Histamine-induced itch can thus be perceived at skin sites where input from mechano-sensitive polymodal nociceptors is blocked. In conclusion, input from mechano-insensitive nociceptors is sufficient to generate histamine-induced itch.

Radioimmunoassay for PMSG and its application to in-vivo studies

A double-antibody radioimmunoassay for PMSG, especially for meauring PMSG in cattle blood after exogenous application, has been developed. A rabbit antiserum against PMSG and pure PMSG for radioiodination were used. There was a strong cross-reaction against equine LH and FSH, but the slight cross-reaction against bovine LH and FSH could be eliminated by adding bovine LH to each tube during the assay. Unspecific, interfering influences of equine or cow serum could be eliminated by adding a constant amount of PMSG-free serum to each tube. PMSG added to 200 microliter of serum could be recovered by this method with a mean of 90 . 5 +/- 9 . 9%. Inhibition curves obtained with pregnant mare serum or cow serum after administration of PMSG were parallel to those obtained with the PMSG standard preparation. The intra-assay coefficient of variation (CV) was 6 . 9%. The inter-assay CV was 12 . 6%. Sensitivity of the assay was 1 mi.u. PMSG/tube. Values of PMSG measured in the serum of pregnant mares by this assay were comparable with those obtained by a bioassay on the same samples. PMSG was still measurable in blood serum about 10 days after injection of 1500-3000 i.u. PMSG. After infusion of 12,000 i.u. PMSG for 3 h (2 heifers), the half-life of PMSG was found to have two components, one of 51 or 40 h and a slower one of 123 or 118 h.

Determination of luteinizing hormone in bovine blood by radioligand receptor assay and comparison with radioimmunological evaluation

A sensitive and specific radioligand receptor assay (RRA) using rat testis homogenate as the receptor source is described for measurement of luteinizing hormone (LH) in bovine blood. Interfering and non-specific substances in blood were removed by means of ion-exchange chromatography on CM-Sephadex C-50. Criteria of validation such as recovery of added LH to plasma or serum, reproducibility, and specificity gave good results. Inhibition curves obtained with bovine plasma and serum were parallel to those obtained with the bovine standard preparation. The range of the dose-response curve was between 0.5-20 ng of bovine LH. The pattern of LH concentrations in purified serum samples under different physiological conditions such as during the oestrus cycle and after administration of GnRH showed a very close correlation whether measured by means of radioimmunoassay (RIA) or receptor assay. Values of RRA-LH were consistently higher than those of RIA-LH. Thus the lower the RIA-LH levels, the more pronounced were the discrepancies between results of both assay systems. The mean ratio of RRA-LH/RIA-LH for basal levels (less than 1 ng RIA-LH/ml plasma) was 17.8 as compared to a mean ratio for higher peak values (more than 20 ng RIA-LH/ml plasma) of only 1.2.