Addition of endocrine therapy to dual anti-HER2 targeted therapy in initial treatment of HER2 + /HR + metastatic breast cancer

PURPOSE

Dual anti-HER2 targeted therapy and chemotherapy is the current first-line standard of care for HER2 + metastatic breast cancer (MBC), with endocrine therapy (ET) the backbone of treatment in hormone receptor positive (HR +) disease. The potential ET benefit in HER2 + /HR + patients is unknown as pivotal dual anti-HER2 clinical trials precluded ET use.

METHODS

Real-world data from a multi-site registry of consecutive HER2 + MBC patients treated at clinician discretion were examined. Patients that were HR + (ER + and/or PR +) and had received first-line chemotherapy alongside trastuzumab and pertuzumab were explored. Of 362 patients in the registry, 215 were excluded due to being HR- (n = 210) or not receiving chemotherapy (n = 5).

RESULTS

Of the 147 patients included, 91 (62%) received concurrent ET and 56 (38%) had not. Comparing the groups, there were no significant differences in age, performance status, metastatic sites, use of previous therapy and de novo metastatic disease. More patients with ER + PR + disease versus those with ER + PR- or ER-PR + received ET (73 vs 45%). The addition of ET was associated with significantly improved 5-year PFS (HR 0.58, CI 0.37-0.89, p = 0.014) and OS (HR 0.52, CI 0.31-0.90, p = 0.018), with no increase in adverse events noted.

CONCLUSION

The addition of ET to first-line dual anti-HER2 therapy post chemotherapy in patients with HER2 + /HR + MBC was associated with major gains in PFS and OS with no safety concerns evident. Further studies of this combination are justified, along with studies of how best to integrate other agents that are active in this patient subset, including CDK4/6 inhibitors.

Telehealth in cancer care during the COVID-19 pandemic

INTRODUCTION

The Victorian COVID-19 Cancer Network (VCCN) Telehealth Expert Working Group aimed to evaluate the telehealth (TH) experience for cancer patients, carers and clinicians with the rapid uptake of TH in early 2020 during the COVID-19 pandemic.

METHODS

We conducted a prospective multi-centre cross-sectional survey involving eight Victorian regional and metropolitan cancer services and three consumer advocacy groups. Patients or their carers and clinicians who had TH consultations between 1 July 2020 and 31 December 2020 were invited to participate in patient and clinician surveys, respectively. These surveys were opened from September to December 2020.

RESULTS

The acceptability of TH via both video (82.9%) and phone (70.4%) were high though acceptability appeared to decrease in older phone TH users. Video was associated with higher satisfaction compared to phone (87.1% vs 79.7%) even though phone was more commonly used. Various themes from the qualitative surveys highlighted barriers and enablers to rapid TH implementation.

DISCUSSION

The high TH acceptability supports this as a safe and effective strategy for continued care and should persist beyond the pandemic environment, where patient preferences are considered and clinically appropriate. Ongoing support to health services for infrastructure and resources, as well as expansion of reimbursement eligibility criteria for patients and health professionals, including allied health and nursing, are crucial for sustainability.

Uptake of bone modifying agents in patients with HER2+ metastatic breast cancer with bone metastases - prospective data from a multi-site Australian registry

BACKGROUND AND AIM

International practice guidelines recommend administration of bone modifying agents (BMA) in metastatic breast cancer (MBC) patients with bone metastases to reduce skeletal related events (SRE). Optimal delivery of BMA in routine clinical practice including agent selection and prescribing intervals remains unclear. We aim to describe real-world practice of Australian breast oncologists.

METHODS

Prospective data from February 2015 to July 2020 on BMA delivery to MBC patients with bone metastases was analysed from TABITHA, a multi-site Australian HER2+ MBC registry.

RESULTS

Of 333 HER2+ MBC patients, 171 (51%) had bone metastases at diagnosis, with a mean age of 58.1 years [range 32-87]. 130 (76%) patients received a BMA, with 90 (69%) receiving denosumab and 40 (31%) receiving a bisphosphonate. Patients who received a BMA were more likely to have received concurrent first line systemic anti-HER2 therapy (95% vs 83%, p=0.04), to present with bone-only metastases at diagnosis (24% vs 7%, p=0.02) and less likely to have visceral metastases (51% vs 71%, p=0.03). Ten of 40 (25%) bisphosphonate patients and 45 of 90 (50%) denosumab patients received their BMA at the recommended 4-weekly interval. Prescribing intervals varied over time. Adverse events reported were consistent with clinical trial data.

CONCLUSION

Three-quarters of Australian HER2+ MBC patients with bone metastases receive a BMA, often at different schedules than guidelines recommend. Further studies, including of all MBC subtypes, are warranted to better understand clinicians' prescribing rationale and potential consequences of current prescribing practice on SRE incidence. This article is protected by copyright. All rights reserved.

Abstract P1-18-13: Impact of prior (neo)adjuvant trastuzumab exposure on the efficacy of HER2 targeted therapy for metastatic breast cancer

Background: HER2 targeted therapies, such as trastuzumab, pertuzumab and trastuzumab-emtansine (TDM-1), have improved survival of patients (pts) with HER2+ metastatic breast cancer (MBC). In the pivotal phase III study of pertuzumab/trastuzumab/docetaxel in MBC (NCT00567190), only 10% of pts received prior trastuzumab, whereas in modern practice the majority of recurrent HER2+ MBC pts have received neo(adjuvant) trastuzumab [NAT]. Survival outcomes in the real world setting have not been well described.

Methods: Pts were part of a prospective national registry collecting clinicopathologic, treatment and outcome data for HER2+ MBC pts diagnosed between 10/2006 and 1/2019. Survival was estimated by the Kaplan-Meier method and compared among groups by log-rank test. A multivariable analysis was used to assess the impact of prior trastuzumab-use on survival. Analysis was stratified by estrogen receptor (ER) status to exclude the impact of concurrent endocrine therapy in the ER positive (ER+) subgroup. The TABITHA registry is sponsored by BioGrid Australia with financial support from Roche Products Pty Limited.

Results: Of 254 HER2+ MBC pts in the registry, 225 received HER2 directed therapy in the first-line advanced disease setting and were included for analysis. Median age was 58 years, 100 (44%) had de novo metastatic disease, 131 (58%) had ER+ disease and 24 (11%) had brain metastases. Of the 125 (56%) pts with recurrent disease, 89 (71%) pts received NAT. First-line HER2 therapy was pertuzumab plus trastuzumab in 176 (78%), trastuzumab in 38 (17%), TDM-1 in 9 (4%), and lapatinib or pertuzumab alone in single pts (<1%). Concurrent chemotherapy was given in 205 (91%) pts, all but one case was taxane-based.

The response rate to anti-HER2 therapy among all MBC pts evaluable for response was 42% in pts who received NAT, and 53% in pts who did not (p=0.20). Median progression free survival (PFS) was 16.4 months and 22.6 months, in pts who were trastuzumab-treated and trastuzumab-naïve, respectively (HR 1.44 [95%CI 0.99 - 2.10], p=0.05). The median overall survival (OS) from first-line HER2-directed therapy for MBC was 41.2 months in pts who had prior NAT, and 52.0 months in trastuzumab-naïve pts (HR 1.73 [95%CI 1.04 - 2.86], p=0.03). On multivariable analysis, prior trastuzumab-exposure was no longer significantly associated with survival. Factors significantly associated with PFS were ER status (HR 0.63, p=0.02) and age (HR 1.02, p=0.04), while only age was significantly associated with OS (see table). Among the subset of 93 ER negative (ER-) pts, prior NAT was significantly associated with inferior PFS (HR 1.97 [95%CI 1.11 - 3.52], p=0.02) and OS (HR 2.13 [95% CI 1.00 - 4.57], p=0.046). Multivariable analysis found only age and presence of brain metastases to be significantly associated with OS in the ER- subgroup. NAT exposure did not impact on PFS (HR 1.15, [95% CI 0.70 - 1.90], p=0.58) or OS (HR 1.37, [95% CI 0.68 - 2.73], p=0.37) in ER+ pts.

Conclusions: In pts with HER2+ MBC, receipt of NAT was associated with inferior survival when HER2 targeted therapy was used in the metastatic setting on univariate analysis, but this finding was not seen in a multivariable analysis. Furthermore, the impact of NAT was only observed in the subset of pts with ER- tumors, raising the possibility that the disease-course in ER+ subgroup is not entirely HER2 driven. Survival rates of these HER2+ MBC pts treated in the community are comparable to that reported in clinical trials.

Cox proportional hazard models for OS in MBC on HER2-targeted therapyUnivariableMultivariableHR95% CIPHR95% CIPAdjuvant trastuzumab Y vs N1.731.04 – 2.850.031.370.64 – 2.940.42De novo metastatic disease Y vs N0.610.37 – 1.020.060.810.38 – 1.730.59Estrogen receptor positive vs negative0.880.53 – 1.440.600.690.41 – 1.180.18Brain metastases Y vs N1.800.88 – 3.670.111.960.90 – 4.260.09Age (years)1.021.00 – 1.040.051.031.01 – 1.060.003

Citation Format: Yada Kanjanapan, Dan Tran, Sheau Wen Lok, Peter Gibbs, Richard De Boer, Belinda Yeo, Sally Greenberg, Frances Barnett, Louise Knott, Gary Richardson, Rachel Wong, Michelle Nottage, Ian Collins, Javier Torres, Janine Lombard, Julie Johns, Michael Harold, Laeeq Malik. Impact of prior (neo)adjuvant trastuzumab exposure on the efficacy of HER2 targeted therapy for metastatic breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-18-13.

Novel endodontic sealers induce cell cytotoxicity and apoptosis in a dose-dependent behavior and favorable response in mice subcutaneous tissue

OBJECTIVES

The objective of the present study is to evaluate the in vitro cytotoxicity and in vivo biocompatibility of two novel endodontic sealers: RealSeal XT1 and Sealapex Xpress on the subcutaneous connective tissue of mice.

MATERIALS AND METHODS

The cytotoxicity was assessed by cell viability using the MTT assay (one-way ANOVA), trypan blue test (Mann-Whitney) and cell apoptosis by flow cytometer. For the subcutaneous study, polyethylene tubes filled with the sealers were implanted in 70 BALB/c mice: 6 experimental groups (n = 10/group) and 2 control groups with empty tubes (n = 5/group). At the end of experimental periods (7, 21, and 63 days), the tissue was removed and histotechnically processed. Angioblastic proliferation and edema (Fisher's exact test) were evaluated, besides thickness measurement (μm) of the reactionary granulomatous tissue and neutrophil counts (Kruskal-Wallis and Dunn's post test; Mann-Whitney) (α = 0.05).

RESULTS

MTT assay, trypan blue, and analysis of apoptotic cells showed a dose-dependent direct effect: the more diluted the sealer, the less cytotoxic. Regarding the angioblastic proliferation and edema, difference between the sealers at 7 and 63 days occurred (p < 0.05). Both endodontic sealers initially promoted perimaterial tissue reaction as a foreign body granuloma and thus stimulated favorable tissue responses.

CONCLUSIONS

Both sealers showed a dose-dependent effect and promoted satisfactory subcutaneous tissue response; the sealer Sealapex Xpress was less cytotoxic and more biocompatible than RealSeal XT.

CLINICAL RELEVANCE

The step of root canal filling during endodontic treatment is highly important for the preservation of the periapical tissue integrity. Subcutaneous reaction to endodontic sealers enables scientific basis for clinical use.

Syndrome of inappropriate anti-diuretic hormone secretion secondary to carboplatin after docetaxel-carboplatin-trastuzumab combination for early stage HER-2 positive breast cancer

Carboplatin is a platinum analogue, widely used in the treatment of numerous cancer types including lung, genitourinary and ovarian cancers. It is also used in the adjuvant treatment of human epidermal growth factor receptor 2 positive breast cancer, where a non-anthracycline regimen is preferred. It is considered generally to be less toxic though potentially less efficacious than cisplatin, another platinum compound. Cisplatin is well recognized as causing hyponatremia, through the mechanism of renal salt wasting. Conversely, carboplatin has only rarely been associated with hyponatremia. We report here a case of severe hyponatremia occurring 6 days after adjuvant treatment with a carboplatin-containing chemotherapy regimen for early stage breast cancer. The mechanism of hyponatremia was consistent with the syndrome of inappropriate anti-diuretic hormone secretion based on biochemical and clinical findings, and response to fluid restriction. With no previously reported cases of docetaxel-associated or trastuzumab-associated hyponatremia, the causative agent was considered to be carboplatin. Additionally there was no recurrence of hyponatremia on recommencement of docetaxel and trastuzumab therapy. Hyponatremia secondary to carboplatin has been rarely reported in the literature, with only three previously reported cases. Although it is rare, oncologists should be aware of the potential for carboplatin to cause hyponatremia and the need to monitor electrolytes throughout therapy.

Adjuvant chemotherapy for stage II and stage III colon cancer—What is happening in routine practice?

e15046

Background: Randomised studies have defined adjuvant chemotherapy as standard treatment for stage III colon cancer (SIIICC), with multiple options available. For stage II (SII) disease, the selection of patients for adjuvant treatment remains controversial. There remains limited data on clinician decision making regarding adjuvant chemotherapy in routine clinical practice. Methods: A review of patients treated with SII & IIICC at 4 hospitals, utilising data from BioGrid Australia, where clinician choice and rationale were prospectively documented. Results: 372 patients (37%) with SII and 307 (30%) with SIIICC were identified from 1015 CC patients treated from January 2003 till November 2008. Median age was 68 years, 51% were male; 49% female. 66 (25%) of patients with SIIICC were not offered chemotherapy, predominantly due to advanced age or co-morbidity. Since oxaliplatin and capecitabine became widely available in 2005, 66% of treated patients have received oxaliplatin based therapy, 15% bolus 5-FU alone and 19% capecitabine. For SII disease, overall 81 (26%) pts received adjuvant chemotherapy. Age was the dominant influence on treatment choice with 41% aged 70 (p<0.001) receiving treatment. Patients with high risk features were also more likely to receive adjuvant therapy. (p= 0.006 for those with lymphovascular invasion and p= 0.0068 for those with T4 tumours). Dose reductions and completion rates were similar for SII and III disease, and for older and younger patients. Conclusions: Over 25% of patients with SIIICC do not receive adjuvant chemotherapy in routine practice, with physicians basing non-treatment recommendations predominantly on patient age and co-morbidity. Where treatment is used, oxaliplatin-based therapy is the dominant regimen, except in older patients. In SIICC, adjuvant chemotherapy is used in one in four patients, more frequently in younger patients and those with high risk features.

No significant financial relationships to disclose.

The use of lumbar spinal stabilization techniques during the performance of abdominal strengthening exercise variations

AIM

The lumbar spinal stabilization techniques in abdominal hollowing and bracing are known to facilitate the level of activity in the muscles transversus abdominis and obliquus internus (TA/OI). The relative timing of activation and the effect of combination with other tasks are currently unknown. The objective of this study was to determine whether the performance of abdominal hollowing and bracing could promote the voluntary preferential recruitment of TA/OI muscles when performed prior to abdominal strengthening exercise variations.

METHODS

The trunk muscles TA/OI, rectus abdominis and obliquus externus were investigated using surface EMG. A pressure transducer under the lumbar spine detected spinal movement. Eighteen male subjects performed a series of 4 abdominal strengthening exercise variations. Pressure cuff and electromyographic onset times were collected and analyzed.

RESULTS

TA/OI muscle site was recruited significantly earlier than the upper rectus abdominis site for the hollow with curl exercise. The TA/OI site was also ranked as first activated site in the majority of subjects during exercises where stabilization techniques of hollowing and bracing were used.

CONCLUSIONS

Abdominal hollowing was an effective method for selective preferential voluntary recruitment of TA/OI site prior to the performance of the curl type abdominal strengthening exercise variation. The other variations brace with curl and hold and hollow with rotation also tend to recruit TA/OI site first, however the timing was not significantly different.

Comparison of laterally condensed .06 and .02 tapered Gutta-Percha and sealer in vitro

The purpose of this in vitro study was to compare the quality of the seal in canals prepared in a standardized manner and obturated with a .06 or a .02 tapered gutta-percha master cone using lateral condensation. Forty-four extracted human anterior teeth with single, straight canals were divided into two experimental groups of 20 teeth each and two control groups of 2 teeth each. The teeth were instrumented with Series 29 Profile .06 tapered rotary nickel-titanium files to a master apical file of 0.46 mm. Teeth in group 1 were obturated with a .02 tapered master gutta-percha cone and Roth 801 sealer using lateral condensation. Teeth in group 2 were obturated similarly, except a .06 tapered master gutta-percha cone was used. The depth of spreader penetration was recorded in millimeters. Positive control teeth were instrumented but not filled. Negative control teeth were instrumented, obturated, and externally sealed. The teeth were placed into a coronal leakage apparatus that contained an upper and lower reservoir of trypticase soy broth separated by the tooth. A 24-h growth of Proteus vulgaris in 0.25 ml of trypticase soy broth was placed in the coronal reservoir every 7 days for 70 days and incubated at 37 degrees C. Student's t test was used to determine whether there was a difference in spreader penetration between the groups, and a Fisher's exact test was used to determine whether there was a difference in bacterial leakage. The positive and negative controls validated the testing model. When a .02 tapered master cone was used, the spreader penetrated significantly closer to working length than when a .06 tapered master cone was used (p < 0.05). The difference between the groups in the number of samples that demonstrated complete bacterial penetration was not significant (p > 0.05).

A turnover study in the male rat of plasma-bound 59Fe, 114Inm and 109Cd with particular reference to the gonad

After intravenous doses of the plasma-bound radionuclides 59Fe, 114Inm and 109Cd, only a minute percentage localizes in the rat testis and remains largely unchanged with time. Intratesticular injection of appropriately reduced volumes led to much higher proportionate percentage retention of 14, 65 and 11 for 59Fe, 114Inm and 109Cd, respectively. By this route, significant feedback of the elements escaping initial binding was prevented. Distinct but different testicular turnovers were now discernible. As a receptor of fluid and spermatozoa from the testicular tubules, the epididymis provides an indication of entry into and interaction of the metals with spermatogenic cells. For 59Fe no measurable changes were detected, whereas a progressive increase in epididymal 114Inm occurred, which had not reached a plateau by 70 days. 109Cd, now demonstrated within the testicular tubules by autoradiography, remained at constant organ level for upwards of 16 days but had declined by 25% by 57 days. At this point, the epididymis showed a five-fold increase in the radionuclide, declining to one-half this value by 126 days. Since 109Cd is carrier free, the data reflect a body turnover of dietary cadmium. These results, overall, are compatible with the entry of a proportion of each radionuclide into the seminiferous tubules and reaction with spermatogenic cells. Possible interpretations of the observed differences are presented.

Pulpal response to restorative procedures and materials

This paper reviews the pulpal response to common restorative procedures and dental materials. Pulpal inflammation and dentin hypersensitivity are commonly associated with routine restorative procedures. Although it is not possible to avoid injury to the pulp completely, in order to prevent unnecessary adverse effects, the practicing dentist should be aware of the potential dangers involved. This article provides a current review of recent findings of the pulpal response to glass ionomer cements and acid-etch composite resin materials.

Demonstration of Bacteroides intermedius in periapical tissue using indirect immunofluorescence microscopy

The presence of bacteria in periapical lesions of teeth with necrotic pulp has been demonstrated by microbiological sampling of periapical lesions during endodontic surgery. The purpose of this study was to confirm the presence of Bacteroides intermedius in a periapical granuloma using an indirect immunofluorescence technique. Histologic sections of a periapical granuloma were incubated with a rabbit antiserum to B. intermedius. After incubation with secondary antibody (fluorescein-conjugated goat anti-rabbit IgG), an intense fluorescent staining was observed in areas of the tissue sections. Control tissue sections that were incubated without the antibody remained unstained. The results obtained with the indirect immunofluorescence technique supported our cultural findings that microorganisms, e.g. B. intermedius, were present in the tissue of the periapical granuloma.

The complications of trabeculectomy (a 20-year follow-up)

The complications of trabeculectomy were studied in two groups of patients taken from a stable white population. The first group who had had their operation when it was first introduced 22 years ago, had been previously treated with prolonged medication, the second group had been operated upon recently and had had short-term pre-operative medication. This study confirmed that trabeculectomy predictably reduces the intraocular pressure to within the accepted normal range and that the pressure level below which the intraocular pressure could not be expected to fall was congruent to 14 mm/Hg. It also revealed that although some post operative abnormality was noted in two-thirds of the patients there were no long term problems which could be related to any operative or immediately post-operative complications, including shallow anterior chambers, uveitis and hyphaema. However, there was a long term reduction in the visual acuity and visual fields of about one-third of the patients, which was not related to cataract formation, macular problems, the height of the preoperative intraocular pressure, the amount by which this fell as a result of the surgery, or the amount, length or type of preoperative medication given before the operation. Although there was some increase in cataracts throughout the whole long term group this was mainly in those who had cataract prior to surgery; the increase was not related to operations or any other factor other than corneo-lenticular contact post-operatively.

Periapical bacterial plaque in teeth refractory to endodontic treatment

It has recently been found that bacteria are able to survive and maintain an infectious disease process in periapical lesions of nonvital teeth. The purpose of this study was to examine the surfaces of root tips removed during surgical-endodontic treatment for the presence of microorganisms. A full thickness flap was reflected under strict surgical asepsis and the periapical lesions were enucleated and removed. About 2-3 mm of the root was cut off, rinsed in sterile saline and placed in 10% neutral-buffered formalin. Upon fixation, the root tips were dehydrated, air-dried and given an electrically conducting coat of gold in a vacuum evaporator. The root tips were then studied in a Jeol, JSM-U3 scanning electron microscope, usually operated at 20 kV. The root surfaces were covered with soft tissue, except at the apex of the roots, where a continuous, smooth and structureless coating was seen, apparently adjacent to the apical foramen. At higher magnification a variety of bacterial forms were recognized in the smooth coating. A bacterial plaque was observed in irregularities of the surfaces between fiber bundles and cells and in crypts and holes. The bacteria were held together by an extracellular material and the plaque was dominated by cocci and rods. Fibrillar forms were recognized as well, often with cocci attached to their surfaces.

Differentiation of radicular cyst and granulomas using computerized tomography

The purpose of this investigation was to study periapical lesions by means of computerized tomography to ascertain if this noninvasive method could be of value in distinguishing between radicular cysts and granulomas. Periapical radiographs were taken of the teeth of 60 human cadavers. Periapical radiolucencies were seen in conjunction with 33 teeth. Based on the periapical radiographs, an oral radiologist (J.P.) attempted to select 4 granulomas and 4 cysts from the 33 radiolucencies. Computerized tomography was performed on the root tips and the periapical lesions of these 8 teeth. The roots and periapical lesions were then surgically removed and prepared histologically for microscopic examination. In the tomographs, 7 of the periapical lesions had a cloudy appearance with a density similar to each other and to the surrounding soft tissue. In the eighth lesion a homogeneous dark area with a distinctly lower density could be distinguished from surrounding cloudy areas. Histologically, the dark area was shown to be an epithelialized cyst cavity. The other 7 lesions were granulomas. Thus, a cyst could be differentiated from periapical granulomas by computerized tomography because of a marked difference in density between the content of the cyst cavity and granulomatous tissue.

In vivo sealing ability of calcium hydroxide-containing root canal sealers

It was the purpose of this study to determine the sealing ability of 2 commercially available calcium hydroxide-containing root canal sealers, CRCS and Sealapex. One hundred sixty single-rooted human teeth were used. The clinical crowns were removed and the roots were cleaned mechanically and by immersion for 24 h in 5% sodium hypochlorite. The root canals were then instrumented to size 80 at the apical foramen and the roots were sterilized by gamma-radiation. Under aseptic conditions the root canals were filled with a gutta-percha master cone size 70 and Sealapex (48 roots), CRCS (48 roots), and a zinc oxide-eugenol type sealer, Roth 801 (50 roots). The coronal aspects of the root canals were then sealed with zinc oxide-eugenol cement. In order to bring the roots and root filling materials in contact with tissue and tissue fluids, the roots were implanted subcutaneously in rabbits for 90 days and 1 year. Leakage as demonstrated by penetration of India ink was evaluated using a stereomicroscope. The best results were obtained with CRCS. Significantly less leakage occurred with both calcium hydroxide-containing sealers than with the traditional zinc oxide-eugenol sealer.

Fluorescent inhibitors of a cell surface protease used to locate leukaemia cells in kidney sections

Guanidinobenzoatase is a trypsin-like protease on the surface of cells capable of migration, for example leukaemia cells. We have used a number of fluorescent probes that are competitive inhibitors of guanidinobenzoatase to locate leukaemia cells in resin sections of kidney tissue obtained from leukaemic rats. We have demonstrated how this competitive inhibition system can be used to direct desired molecules (such as cytotoxic drugs) to these cells and to monitor the arrival of such compounds at the active site of guanidinobenzoatase. The principles developed in this study could equally well be applied to other enzymes on other cells provided suitable competitive inhibitors were designed. The presence of an enzyme on the surface of a cell can be used to direct molecules to that cell provided that these molecules contain a functional group that acts as an inhibitor for the chosen enzyme.

Is 2% hydroxypropylmethylcellulose a safe solution for intraoperative clinical applications?

We examined 2% hydroxypropylmethylcellulose prepared for clinical intraocular surgical procedures in various laboratories. Each sample contained a variety of particulate debris of botanical origin, although in varying amounts. The identified material was also seen in a sample of the raw material from which all the clinical material had been prepared. Our conclusion is that filtration methods, which are the physical methods used to purify the product, are at worst ineffective and at best inadequate. Until proper laboratory and clinical studies confirm an acceptable level of adverse reactions, we recommend that this material not be used clinically.

Tissue response to anodyne medicaments

The tissue-irritating effect of anodyne medicaments was studied via enzyme histochemical evaluation of muscle tissue (screening test) and pulp tissue (usage test). Of the medicaments tested, formocresol was the most irritating, followed by Cresatin, eugenol, and oil of pimenta leaf. The effects of Cresatin, eugenol, and oil of pimenta leaf were not statistically distinguishable.