Effectiveness of a 3 + 0 pneumococcal conjugate vaccine schedule against invasive pneumococcal disease among a birth cohort of 1.4 million children in Australia

BACKGROUND

Most studies use indirect cohort or case-control methods to estimate vaccine effectiveness (VE) of 7- and 13-valent pneumococcal conjugate vaccines (PCV7 and PCV13) against invasive pneumococcal disease (IPD). Neither method can measure the benefit vaccination programs afford the unvaccinated and many studies were unable to estimate dose-specific VE. We linked Australia's national immunisation register with health data from two states to calculate IPD incidence by vaccination status and VE for a 3 + 0 PCV schedule (doses at 2, 4, 6 months, no booster) among a cohort of 1.4 million births.

METHODS

Births records for 2001-2012 were probabilistically linked to IPD notifications, hospitalisations, deaths, and vaccination history (available until December 2013). IPD rates in vaccinated and unvaccinated children <2 years old were compared using Cox proportional hazards models (adjusting for potential confounders), with VE = (1 - adjusted hazard ratio) × 100. Separate models were performed for all-cause, PCV7, PCV13 and PCV13-non-PCV7 serotype-specific IPD, and for Aboriginal and non-Aboriginal children.

RESULTS

Following introduction of universal PCV7 in 2005, rates of PCV7 serotype and all-cause IPD in unvaccinated children declined 89.5% and 61.4%, respectively, to be similar to rates in vaccinated children. Among non-Aboriginal children, VEs for 3 doses were 94.2% (95%CI: 81.9-98.1) for PCV7 serotype-specific IPD, 85.6% (95%CI: 60.5-94.8) for PCV13-non-PCV7 serotype-specific IPD and 80.1% (95%CI: 59.4-90.3) for all-cause IPD. There were no statistically significant differences between the VEs for 3 doses and for 1 or 2 doses against PCV13 and PCV13-non-PCV7 serotype-specific IPD, or between Aboriginal and non-Aboriginal children.

CONCLUSION

Our population-based cohort study demonstrates that >90% coverage in the first year of a universal 3 + 0 PCV program provided high population-level protection, predominantly attributable to strong herd effects. The size of the cohort enabled calculation of robust dose-specific VE estimates for important population sub-groups relevant to vaccination policies internationally.

Abstract P5-21-26: T-DM1 activity in metastatic HER2-positive breast cancer patients who have received prior trastuzumab and pertuzumab: NSABP B-005

Background :

The pivotal phase III EMILIA trial reported a progression free survival (PFS) rate of 9.6 months and an objective response rate of 43% with T-DM1 in patients with HER2-positive metastatic breast cancer previously treated with trastuzumab and a taxane. However, there is very limited data on the efficacy of T-DM1 in patients who have received prior pertuzumab either neoadjuvantly or as first line therapy in the metastatic setting. The primary goal of this study was to assess the clinical efficacy (tumor response rates and median duration on therapy) of T-DM1 in patients previously treated with pertuzumab and trastuzumab.

Methods:

After IRB approval, a cancer data registry and electronic pharmacy database were utilized to identify breast cancer patients receiving treatment with T-DM1 at Cleveland Clinic and University of Pittsburgh. Patients that received trastuzumab and pertuzumab, in either the neoadjuvant or metastatic setting, with baseline and follow up imaging available for review were identified. Patient charts were reviewed to collect accurate information about the treatment sequencing and outcomes. RECIST version 1.1 was utilized for tumor assessment and patients with measurable disease and non measurable disease were included in the study.

Results:

We identified a total of 23 patients with a median age of 55 years that met the inclusion criteria. 69% percent of patients received T-DM1 as first line or second line therapy and 31% received it as third line or later. All patients had at least 1 measurable lesion. Best overall response showed rates of complete response, partial response and stable disease of 17%, 26% and 22% respectively. 35% patients progressed on first assessment after start of treatment. The median duration on therapy was 5.3 months (range 3 weeks to 33 months) with 43% of patients receiving T-DM1 for greater than 6 months.

Conclusion:

Our results were comparable to those reported by EMILIA trial. T-DM1 has reasonable clinical efficacy in patients who have received prior treatment with pertuzumab and trastuzumab with an overall response rate of 43% and median duration on therapy of 5.3 months.

Citation Format: Tiwari SR, Sussman T, Kota K, Moore HC, Montero AJ, Budd GT, Puhalha S, Abraham J. T-DM1 activity in metastatic HER2-positive breast cancer patients who have received prior trastuzumab and pertuzumab: NSABP B-005 [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-21-26.

Probabilistic linkage of national immunisation and state-based health records for a cohort of 1.9 million births to evaluate Australia's childhood immunisation program

Introduction

Several countries have developed national immunisation registers, but only the Nordic countries have linked their registers to other health data in order to comprehensively evaluate the `real world' effectiveness of vaccines. Nordic countries can link datasets deterministically using the national person identifier, but most countries, including Australia, don't have such an identifier to enable this type of linkage.

Objectives

To describe the process for assembling a linked study cohort that will enable the conduct of population-based studies related to immunisation and immunisation policy.

Methods

National death and immunisation databases along with state health data (notifications of vaccine preventable diseases, perinatal data, hospital admissions and emergency department presentations) up until December 2013 were probabilistically linked (using demographic details) for children born between 1996 and 2012 in two states: Western Australia and New South Wales (42% of Australia's population, combined).

Results

After exclusions there were 1.95 million children in the study cohort (live born children with both a birth and perinatal record which represents 97.5% of all live births in the state perinatal data collections - our source population) and 18.0 million person years of follow up (mean: 9.2 years per child). The characteristics of children in the cohort were generally similar to those only included in state perinatal databases and outcome measures were in keeping with expected figures from unlinked data sources. However, the lack of a dynamic national population register meant immigrants could not be included.

Conclusions

We have been able to develop a similarly comprehensive system to the Nordic countries based on probabilistic linkage methods. Our experience should provide encouragement to other countries with national immunisation registers looking to establish similar systems.

Differential outcomes in patients treated with endocrine therapy for early or locally advanced breast cancer based on BRCA mutation status

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Background: Mutations in BRCA1 and BRCA2 genes lead to defects in DNA repair. Estrogen receptor modulates transcription of genes responsible for cell division, which depends on cell's ability to repair DNA for genomic integrity. Differential efficacy of endocrine therapy for breast cancer, therefore, may be possible depending on the tumor's BRCA mutation status. Methods: Through an IRB approved registry, breast cancer patients tested for BRCA1 and BRCA2 mutations and treated with endocrine therapy for hormone-receptor positive non-metastatic disease were identified. Primary and secondary endpoints were overall survival (OS) and progression-free survival (PFS) respectively. Fisher's exact test or Wilcoxon rank sum test were used to assess differences among subgroups with respect to their characteristics. Cox proportional hazard analysis was used to identify univariate and multivariate risk factors for OS and PFS. Results: Of 115 breast cancer patients tested for BRCA mutations, 63 met the inclusion criteria of whom 16 patients were BRCA 1 or 2 mutation positive and 47 were negative. In the BRCA(+) group, 14 patients (87.5%) had stage I-III disease at diagnosis. In the BRCA(-) group, 5 patients (10.6%) had stage 0 disease while 41 patients (87.2%) had stage I-III disease at diagnosis. Stage at diagnosis was unavailable for 2 BRCA(+) and 1 BRCA(-) patients. Both groups were similar with respect to Her-2 expression status, history of ovarian suppression, age of diagnosis, and age of menopause. Median age was 48 yo in BRCA(+) group, 42 yo in BRCA(-), (p=0.12). Median follow up was 76.1 mos in BRCA(+) and 62.9 mos in BRCA(-) group. OS was worse in BRCA(+) group (HR 7.38, 95% [CI] 1.49–36.4 p=0.014). After adjustment for stage and history of ovarian suppression, the difference remained significant (HR 16.6, 95% [CI] 1.95–142, p=0.010). There was no difference in PFS (HR 2.02, 95% [CI] 0.82–4.96, p=0.13). Conclusions: Patients with BRCA mutation, hormone-receptor positive hereditary breast cancer treated with endocrine therapy had inferior survival compared with similar patients who are BRCA mutation negative. Prospective studies to evaluate the differential effects of endocrine therapy in these populations are warranted.

No significant financial relationships to disclose.

Predictors of permanent menopause after chemotherapy for early-stage breast cancer in premenopausal women

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Background: Optimal choice of endocrine therapy for early-stage breast cancer differs with menopausal status. While amenorrhea is common during adjuvant chemotherapy, there is currently no available test to establish when menopause is permanent. The aim of this study was to determine the age cutoff after which resumption of menses is unlikely following chemotherapy and to assess what additional risk factors may predict for persistent menopause at 5 years after initiation of chemotherapy. Methods: One hundred patients treated with chemotherapy for early-stage premenopausal breast cancer and who remained alive and free of recurrence at least 5 years from the start of treatment were enrolled. Participants were evaluated for current menstrual status and for baseline potential risk factors for menopause: age at start of chemotherapy, race, BMI, smoking history, age at menarche, irregular menses prior to chemotherapy, presence of menses during chemotherapy, type of chemotherapy regimen, hormonal therapy, ovarian protection during chemotherapy, and number of doses of alkylating agent (cyclophosphamide). Recursive partitioning analysis (RPA) was used to identify the age cutoff that best predicts permanent menopause; additional risk factors were assessed using logistic regression analysis. Results: Median age at start of chemotherapy was 43 (range 26–49). RPA identified age >42 at the start of chemotherapy as a significant predictor of permanent menopause (p < 0.001). Cessation of menses during chemotherapy was also associated with permanent menopause (p < 0.001). Both variables remained significant in multivariate analysis (p < 0.001), with the combination of these factors being associated with a 95.4% chance of permanent menopause. Conclusions: In this series, fewer than 5% of premenopausal patients who were at least 42 years old and who experienced cessation of menses during chemotherapy experienced any return of menses over at least 5 years. Upfront use of aromatase inhibitors as adjuvant endocrine therapy for premenopausal hormone-receptor positive breast cancer warrants further investigation for those who are at least 42 years of age and who experience amenorrhea with chemotherapy.

No significant financial relationships to disclose.

Histological profile of tumours from MYCN transgenic mice

BACKGROUND

MYCN is the most commonly amplified gene in human neuroblastomas. This proto-oncogene has been overexpressed in a mouse model of the disease in order to explore the role of MYCN in this tumour.

AIMS

To report the histopathological features of neuroblastomas from MYCN transgenic mice.

METHODS

27 neuroblastomas from hemizygous transgenic mice and four tumours from homozygous mice were examined histologically; Ki67 and MYCN immunocytochemistry was performed in 24 tumours.

RESULTS

Tumours obtained from MYCN transgenic mice resembled human neuroblastomas, displaying many of the features associated with stroma-poor neuroblastoma, including heterogeneity of differentiation (but no overt ganglionic differentiation was seen), low levels of Schwannian stroma and a high mitosis karyorrhexis index. The tumours had a median Ki67 labelling index of 70%; all tumours expressed MYCN with a median labelling index of 68%. The most striking difference between the murine and human neuroblastomas was the presence of tingible body macrophages in the transgenic mouse tumours reflecting high levels of apoptosis. This has not previously been described in human or other murine neuroblastoma models.

CONCLUSIONS

These studies highlight the histological similarities between tumours from MYCN transgenic mice and human neuroblastomas, and reaffirm their role as a valuable model to study the biology of aggressive human neuroblastoma.

Therapeutic radiation for breast cancer in BRCA mutation carriers and contralateral breast cancer (CBC) risk

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Background: BRCA mutation carriers diagnosed with breast cancer are at high risk for contralateral second primary breast cancers. Mutations in BRCA1 and BRCA2 lead to defects in DNA repair. Radiation treatment for breast cancer is felt to increase risk of CBC, but the interaction between BRCA status and local radiation therapy with respect to their effects on CBC is unclear. Methods: Through an IRB approved database registry at the Cleveland Clinic, breast cancer patients tested for BRCA1 and BRCA2 mutations were identified and evaluated for CBC events and radiation treatment history. Patients with inadequate clinical follow-up, those with bilateral synchronous breast cancer and those undergoing bilateral mastectomy within one year of the original breast cancer diagnosis were excluded from the analysis. Chi-square test was used to compare CBC rates with or without prior radiation separately in patients testing positive and those testing negative for BRCA mutations. Results: Of 115 identified breast cancer patients tested for BRCA mutations, 57 met the inclusion criteria. Twenty-one carried BRCA1 or BRCA2 mutations and 36 tested negative for these mutations. Median follow-up for the two groups was 69.5 months (92 months in BRCA positive group and 51.5 months in BRCA negative group). Median age at diagnosis was 45 years (41 years in BRCA positive group and 48.5 in BRCA negative group). Among the 21 carriers, 9 patients (43%) developed CBC while only 3 of 36 patients (8%) testing negative for BRCA mutations developed CBC. Thirteen of 21 mutation carriers (62%) had received radiation treatment for the original cancer: CBC occurred in 3 of 13 (23%) radiated patients and 6 of 8 (75%) patients who had not received radiation (p= 0.02). Among 36 patients with negative BRCA testing, 30 (83%) had received radiation: CBC occurred in 3 of 30 (10%) mutation negative patients who had received prior radiation and in 0 of the 6 patients who had not received radiation (p = 0.42). Conclusions: CBC incidence was higher among BRCA mutation carriers than a control group suspected of having hereditary breast cancer but testing negative for these mutations. The use of radiation in the presence of a BRCA mutation, however, does not appear to further increase the risk for CBC.

No significant financial relationships to disclose.

Managing menopause after breast cancer: balancing risks and benefits

Many women now survive breast cancer, but find themselves at increased risk of menopausal complications. How to manage menopause after breast cancer is a complex issue, given that estrogen has a role in the development of breast cancer and valid concerns exist about estrogen replacement therapy in patients who have had breast cancer. This article explores the relationship between estrogens and breast cancer and discusses management options for a variety of menopausal complications in breast cancer survivors.

Breast cancer and pregnancy

A diagnosis of breast cancer during pregnancy or the postpartum period is an unfortunate occurrence. Hormonal factors appear to play an important role early on in the development of breast cancer; however, pregnancy itself does not clearly influence the outcome of an established breast cancer. Diagnosis can be challenging in a pregnant woman and delays in diagnosis are common. Treatment decisions must take into consideration not only toxicity to the mother, but short- and long-term consequences for the fetus as well. Other special considerations with pregnancy-associated breast cancer include the timing of delivery, the potential for nursing, and concerns for future fertility. In general, management of pregnancy associated breast cancer follows the same principals as in non-pregnant patients of similar age. With thoughtful application of available therapies, outcome can be optimized for both the mother and her child.

Fertility and the impact of systemic therapy on hormonal status following treatment for breast cancer

Issues of long-term toxicity from treatment for breast cancer, including the induction of premature ovarian failure, appear to be of increasing importance for breast cancer survivors. The incidence of treatment-related amenorrhea is related to patient age and to the treatment regimen. Whereas the induction of ovarian failure may be advantageous with respect to breast cancer outcome, it is not clear that there is any advantage to permanent menopause over reversible hormonal manipulations. In addition, menopause may be associated with a variety of adverse health effects. Although nonhormonal therapies are available to manage many of the consequences of menopause, avoidance of chemotherapy-related ovarian toxicity may provide the best prospects for fertility after treatment. Pregnancy after breast cancer is a realistic consideration for some breast cancer survivors and is not clearly detrimental to either the mother or her offspring.

Progressive intermediate-grade non-Hodgkin's lymphoma after high-dose therapy and autologous peripheral stem-cell transplantation: changing the natural history with monoclonal antibody therapy

The prognosis of patients with progressive intermediate-grade non-Hodgkin's lymphoma (NHL) after high-dose chemotherapy and autologous peripheral stem-cell transplantation (PSCT) is poor, with survival measured in months. The advent of monoclonal antibody therapy for NHL has created new options for effective therapy with relatively mild side effects. We report on two patients with progressive intermediate-grade NHL after PSCT who were treated with monoclonal antibody therapy. Both patients initially received rituximab (unlabeled anti-CD20 monoclonal antibody) and were subsequently treated with (90)Y-epratuzumab (yttrium-90-labeled humanized anti-CD22 monoclonal antibody) at relapse. One patient received (90)Y-epratuzumab alone while the other was treated with higher doses in combination with autologous peripheral stem-cell infusion. Both patients achieved a rapid response to the radiolabeled antibody with minimal toxicity. Monoclonal antibody therapy may be an effective and tolerable treatment for progressive NHL after PSCT.

Adjuvant therapy of colon cancer

Colon cancer is an important cause of cancer-related mortality. A series of clinical trials of adjuvant systemic therapy have been performed in attempt to establish means to improve outcome in this disease. By the early 1990s, a role for 5-fluorouracil (5-FU)-based chemotherapy in stage III colon cancer had been firmly established. The precise role for chemotherapy in stage II disease remains under investigation. Progress continues toward optimizing the schedule and duration of systemic therapy, allowing for maximal efficacy with a minimum of toxicity. It appears that approximately 6 months of 5-FU and leucovorin are as effective as more prolonged regimens. Levamisole does not appear to add to the benefit of 5-FU and leucovorin. Several newer agents such as the oral fluorinated pyrimidines, irinotecan (CPT-11) and oxaliplatin have demonstrated activity in metastatic colon cancer and hold promise as potentially effective drugs to be tested in the adjuvant setting.

Autologous stem-cell transplant after conventional dose adjuvant chemotherapy for high-risk breast cancer: impact on the delivery of local-regional radiation therapy

BACKGROUND

High-dose chemotherapy with autologous stem-cell transplantation is used increasingly in the treatment of poor-prognosis primary breast cancer. Because these patients may be cured with standard multimodality therapy, it is important to address both the efficacy of transplantation, and its effect on the delivery of standard treatments including local radiation therapy.

PATIENTS AND METHODS

Patients with high risk primary breast cancer were treated with high-dose cyclophosphamide and thiotepa and stem-cell transplant following surgery and conventional-dose adjuvant chemotherapy. Outcome, including sites of failure and delivery of local radiation therapy, was assessed for 103 patients.

RESULTS

Overall and disease-free survival rates at 18 months were 83% (+/- 4%) and 77% (+/- 4%) respectively. Twenty patients (19.4%) received radiation therapy prior to transplant. Of the remaining 83, 77 received radiation therapy after transplant. Overall, 5 (19.2%) of 26 first sites of recurrence were local alone. For patients receiving radiation prior to transplant, 3 of 7 (43%, 95% CI: 6%-80%) sites of first recurrence were local, while 2 of 19 (10.5%, 95% CI: 0%-24.5%) sites of first recurrence were local alone in patients receiving post-transplant radiation or no radiation.

CONCLUSION

Transplantation does not appear to significantly compromise the delivery or outcome of local radiation therapy for primary breast cancer.

Open reduction-fixation of mandibular subcondylar fractures. A review

From 1973 to 1990, 392 mandibular subcondylar fractures were treated at the University of California, Davis, by the Otolaryngology Department. Of these, 17% were handled by open reduction and internal fixation. Twenty-one patients from this group were located for follow-up at an average interval of 64 months. Retrospective review shows the operation to be safe, with few complications and no permanent sequelae. Patient examination often revealed abnormalities of occlusion and mandibular function; however, these objective findings did not correlate well with patients' relative lack of subjective complaints. An 86% incidence of roentgenographic evidence of condylar disease after open reduction and internal fixation was found. We question the long-term efficacy of open reduction and internal fixation in restoring fracture alignment and maintaining mandibular height given the high rate (86%) of condylar disease in our patient population.

Acoustic isolation reduces degeneration of the ventral cochlear nuclei in Mongolian gerbils

The role of auditory experience in the development of spongiform degeneration in the cochlear nuclei of Mongolian gerbils was studied by comparing results of animals exposed to either high or low levels of ambient noise. Gerbils reared in a typical vivarium experienced higher levels of ambient noise than animals reared in acoustic isolation chambers. Animals reared in the colony room showed a much greater number density and area density of spongiform lesions in the CN than did gerbils reared in acoustic isolation. The differences in the number and extent of spongiform lesions between the two groups of gerbils appeared to reflect their differences in exposure to ambient noise. These differences in lesion number and extent were most pronounced in the tonotopic regions of the PVCN which correspond to the greatest differences in the spectral characteristics of the ambient noise to which the animals were exposed. These results were compared with results previously obtained from gerbils with loss of hearing experimentally induced by a conductive block or by sensorineural damage. The lesion numbers and extent reflected the auditory experience of each group; in descending order, colony-reared, isolate, conductive-block, sensorineural loss. These results strongly support the hypothesis that this gerbilline encephalopathy is directly related to auditory functional activity.

Effects of profound sensorineural loss on gerbilline auditory encephalopathy

To investigate the role of acoustic stimulation in the development of spongiform degeneration in the cochlear nuclei of Mongolian gerbils, the right cochlea in 8 juvenile gerbils was chemically treated by placing sodium chloride (NaCl) crystals on the cochlear round window membrane. Sixty days after NaCl treatment there was extensive damage to the strial, sensorineural and supporting cells of the treated inner ear. The cochlear damage was accompanied by a dramatic decrease in the number and the extent of the spongioid lesions in the ipsilateral cochlear nuclei compared to the contralateral (control) cochlear nuclei. These results lend further support to the hypothesis that the progress of this disorder is related to auditory function.

Linear localized coumarin necrosis

We report a 55-year-old man with coumarin necrosis. This drug eruption is sometimes a devastating gangrenous process in sites with abundant underlying adipose tissue. In our patient, however, it assumed an evanescent limited linear distribution on the skin, prompting this report.

Use of a low-ionic-strength medium in manual tests for antibody detection

The present observations confirm the value of suspending red blood cells in a low-ionic-strength medium in the first stage of the indirect antiglobulin test; that is, during the period of incubation with antibody-containing serum. The main advantage of this procedure is to shorten the time of incubation. In this respect a low-ionic-strength medium appears to be superior to albumin as a suspending medium for the red blood cells. A further advantage is to increase the uptake of certain antibodies; this effect was pronounced with selected Rh antibodies believed to be of low affinity.

Successful transfusion of Chido-positive blood to two patients with anti-Chido

Two cases are described in this report in which patients with anti-Chido in the serum were transfused with Chido-positive blood. Since there was evidence of normal survival of the transfused red blood cells, these findings do not support a suggestion that patients with anti-Chido may require transfusion with Chido-negative blood. In spite of the apparently normal survival of the Chido-positive blood, a previous report in which it was shown that weakly Chido-positive blood can stimulate the production of anti-Chido was confirmed.

The effect of foetal removal on the blood pressure in steroid hypertensive rats

In unilaterally nephrectomized hypertensive rats receiving DOCA, cortisone and saline the blood pressure falls after the removal of the foetuses as though the animals continued to be pregnant with the foetuses in situ. On the other hand, when the foetuses are removed from steroid hypertensive animals in which the maternal kidneys remain intact the blood pressure remains at hypertensive levels. The metrial gland part of the placenta appears histologically viable after foetal removal.

We conclude from the present and earlier experiments that the usual hypotensive effect of pregnancy in hypertensive animals is due to a vasodepressor agent produced by the foetuses and the metrial gland moiety of the placenta and that the activity of this agent is subject to maternal renal function.

A relation between these experiments and human pregnancy hypertension is not clear but we suggest that in human pregnancy, hypertension could be due either to failure of the foetoplacental vasodepressor or vasodilator agent or to destruction or excretion of this agent by the maternal kidney.

The duration of the fall of blood pressure following the induction of deciduomata and the administration of progesterone in steroid hypertensive rats

Experimental deciduomata produce a protracted fall of blood pressure in steroid hypertensive rats. The fall begins at between 9 and 13 days of pseudopregnancy, lasts for between 8 and 14 days and is then followed by a restoration to higher levels between 17 and 24 days. The metrial gland of the deciduomata is thought to be responsible for the fall.

Parenteral progesterone has two main effects. It enhances the degree of the fall of blood pressure and also prolongs the survival of deciduomata to beyond 22 days of pseudopregnancy. Progesterone does not alter the time of onset nor the duration of the hypotensive episode and the return of the blood pressure to higher levels takes place even though the metrial gland of the deciduomata is still viable and progesterone still being administered.

It is considered that the duration of the hypotensive episode is determined either by a changed function of the metrial gland cells with duration or to an entirely different but unknown mechanism.

The present findings suggest that the hypotensive effect of pregnancy in hypertensive rats is a related phenomenon and is due in part to the function of metrial gland cells of the pregnancy decidua under the influence of progesterone.

The fall of blood pressure following induction of deciduomata in steroid hypertensive rats receiving progesterone

Experimental deciduomata and progesterone together lower the blood pressure in the steroid hypertensive rat from the 5th to 10th day of decidual growth i. e. from the 10th to 15th day of pseudopregnancy. This would suggest that the fall of blood pressure at an equivalent time of gestation in hypertensive pregnant rats could be due to the maternal decidua under the influence of progesterone. It is further considered that the metrial gland of the deciduoma is more likely to be responsible for the hypotensive effect and by comparison that the metrial gland is implicated in the hypotensive effect of pregnancy.

Progesterone alone also exerts a minor hypotensive effect in those animals in which a nephrectomy forms part of the hypertension regimen and indicates one way in which a maternal renal factor could influence blood pressure responses in hypertensive pregnant rats.

Effect of the experimental deciduoma on steroid hypertension in the rat

Experimental deciduomas which are maintained for 5 to 6 days do not lower the blood pressure in steroid hypertensive rats. In animals maintained longer only the metrial gland of the deciduoma survives but this too does not have a hypotensive action.

It is concluded that the maternal decidual reaction in pregnant hypertensive rats is not responsible for the fall of blood pressure when this occurs at an equivalent time of gestation of up to 10 or 11 days and that the metrial gland is not responsible for the fall of blood pressure at whatever time the fall occurs during gestation.