Roadmap to safety: a single center study of evidence-informed approach to placenta accreta spectrum

Objective

To assess the impact of an evidence-informed protocol for management of placenta accreta spectrum (PAS).

Methods

This was a retrospective cohort study of patients who underwent cesarean hysterectomy (c-hyst) for suspected PAS from 2012 to 2022 at a single tertiary care center. Perioperative outcomes were compared pre- and post-implementation of a standardized Multidisciplinary Approach to the Placenta Service (MAPS) protocol, which incorporates evidence-informed perioperative interventions including preoperative imaging and group case review. Intraoperatively, the MAPS protocol includes placement of ureteral stents, possible placental mapping with ultrasound, and uterine artery embolization by interventional radiology. Patients suspected to have PAS on prenatal imaging who underwent c-hyst were included in the analysis. Primary outcomes were intraoperative complications and postoperative complications. Secondary outcomes were blood loss, need for ICU, and length of stay. Proportions were compared using Fisher's exact test, and continuous variables were compared used t-tests and Mood's Median test.

Results

There were no differences in baseline demographics between the pre- (n = 38) and post-MAPS (n = 34) groups. The pre-MAPS group had more placenta previa (95% pre- vs. 74% post-MAPS, p = 0.013) and prior cesarean sections (2 prior pre- vs. 1 prior post-MAPS, p = 0.012). The post-MAPS group had more severe pathology (PAS Grade 3 8% pre- vs. 47% post-MAPS, p = 0.001). There were fewer intraoperative complications (39% pre- vs.3% post-MAPS, p < 0.001), postoperative complications (32% pre- vs.12% post-MAPS, p = 0.043), hemorrhages >1l (95% pre- vs.65% post-MAPS, p = 0.001), ICU admissions (59% pre- vs.35% post-MAPS, p = 0.04) and shorter hospital stays (10 days pre- vs.7 days post-MAPS, p = 0.02) in the post-MAPS compared to pre-MAPS patients. Neonatal length of stay was 8 days longer in the post-MAPS group (9 days pre- vs. 17 days post-MAPS, p = 0.03). Subgroup analyses demonstrated that ureteral stent placement and uterine artery embolization (UAE) may be important steps to reduce complications and ICU admissions. When comparing just those who underwent UAE, patients in the post-MAPS group experienced fewer hemorrhages greater five liters (EBL >5l 43% pre- vs.4% post-MAPS, p = 0.007).

Conclusion

An evidence-informed approach to management of PAS was associated with decreased complication rate, EBL >1l, ICU admission and length of hospitalization, particularly for patients with severe pathology.

Trust in prenatal exome sequencing for expectant families facing unexplained fetal anomalies

OBJECTIVE

Despite exome sequencing (ES) becoming increasingly incorporated into the prenatal setting, few studies have elucidated motivations for and trust in ES and genomic research among a diverse cohort of patients and their partners.

METHODS

This is a qualitative study that involved semi-structured interviews with pregnant or recently pregnant individuals and their partners, interviewed separately, in the setting of ES performed through research for a fetal structural anomaly. All interview transcripts were coded thematically and developed by a multidisciplinary team.

RESULTS

Thirty-five individuals participated, the majority of whom (66%) self-identified as a racial or ethnic group underrepresented in genomic research. Many patients and their partners expressed trust in the healthcare system and research process and appreciated the extensive testing for information and closure. There were nonetheless concerns about data privacy and protection for individuals, including those underrepresented, who participated in genomic testing and studies.

CONCLUSION

Our findings illustrate important elements of motivation, trust and concern related to prenatal ES performed in the research setting, taking into account the perspectives not only of diverse and underrepresented study participants but also partners of pregnant individuals.

The impact of histologic subtype on primary site surgery in the management of metastatic lobular versus ductal breast cancer: a population based study from the National Cancer Database (NCDB)

PURPOSE

Primary site surgery for metastatic breast cancer improves local control but does not impact overall survival. Whether histologic subtype influences patient selection for surgery is unknown. Given differences in surgical management between early-stage lobular versus ductal disease, we evaluated the impact of histology on primary site surgery in patients with metastatic breast cancer.

METHODS

The National Cancer Database (NCDB, 2010-2016) was queried for patients with stage IV HR-positive, HER2-negative invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC). We compared clinicopathologic features, primary site surgery rates, and outcomes by histologic subtype. Multivariable Cox proportional hazard models with and without propensity score matching were used for overall survival (OS) analyses.

RESULTS

In 25,294 patients, primary site surgery was slightly but significantly less common in the 6,123 patients with ILC compared to the 19,171 patients with IDC (26.9% versus 28.8%, p = 0.004). Those with ILC were less likely to receive chemotherapy (41.3% versus 47.4%, p < 0.0001) or radiotherapy (29.1% versus 37.9%, p < 0.0001), and had shorter OS. While mastectomy rates were similar, those with ILC who underwent lumpectomy had significantly higher positive margin rates (ILC 15.7% versus IDC 11.2%, p = 0.025). In both groups, the odds of undergoing surgery decreased over time, and were higher in younger patients with T2/T3 tumors and higher nodal burden.

CONCLUSION

Lobular histology is associated with less primary site surgery, higher positive margin rates, less radiotherapy and chemotherapy, and shorter OS compared to those with HR-positive HER2-negative IDC. These findings support the need for ILC-specific data and treatment approaches in the setting of metastatic disease.

Quantifying hormone receptor status in lobular breast cancer in an institutional series: the relationship between estrogen and progesterone receptor status and outcomes

PURPOSE

Recent guidelines defined a new reporting category of ER-low-positive breast cancer based on immunohistochemistry (IHC). While low positivity of either hormone receptor is uncommon in invasive lobular carcinoma (ILC), we sought to investigate whether relatively low hormone receptor positivity was associated with tumor characteristics and patient outcomes in a single institutional cohort.

METHODS

We searched an institutional database for cases of stage I-III ILC with available IHC reports. Based on prior published categories in ILC, ER was classified as low, medium, or high as defined by ER staining of 10-69%, 70-89%, and ≥ 90% respectively. PR low and high tumors were defined by < 20%, or ≥ 20% staining respectively. We used chi-squared tests, t-tests, and Cox proportional hazards models to evaluate associations between ER/PR categories and tumor characteristics or disease-free survival (DFS).

RESULTS

The cohort consisted of 707 ILC cases, with 11% of cases categorized as ER low, 15.1% as medium, and 73.8% as high. The majority (67.6%) were PR high. Patients with ER low/medium expression were significantly younger, and more likely to also have PR low and/or HER2 positive tumors compared to those that were ER high. In a Cox proportional hazards model adjusting for age, stage, grade, pleomorphic histology, and treatment, ER category was not prognostic for DFS, but PR negative and PR low status each had significantly worse DFS compared to PR high status (HR 3.5, 95% CI 1.8-6.7, p < 0.001; and HR 2.0, 95% CI 1.1-3.5, p = 0.015, respectively).

CONCLUSION

These findings highlight the relevance of quantifying ER and PR within ILC.

Tamoxifen or aromatase inhibitors with ovarian function suppression in pre-menopausal stage I-III lobular breast cancer

While adjuvant treatment with the selective-estrogen receptor modulator (SERM) tamoxifen has been the standard of care for pre-menopausal patients with hormone receptor (HR) positive breast cancer, recent trials showed a benefit of aromatase inhibitors (AI) and ovarian function suppression (OFS) for some patients. The approach to endocrine therapy has not been well studied in pre-menopausal patients with invasive lobular carcinoma (ILC). We identified 202 pre-menopausal patients with HR positive stage I-III ILC in an institutional database. We investigated factors associated with endocrine therapy type and determined changes in systemic therapy from 1990-2021. We evaluated associations between endocrine therapy type and disease-free survival (DFS) with a multivariate Cox proportional hazards model. Of 202 patients, most (69.3%) were prescribed a SERM (99.3% tamoxifen). Those who received an AI had significantly higher stage disease. Over time, use of OFS and AI increased significantly in stage II or III cases (from 0% in 1990 to 56% after 2015 for stage II; from 0% to 80% after 2015 for stage III). Concurrently, adjuvant chemotherapy use significantly decreased in stage II cases (from 67% to 19%). In an exploratory multivariable model, longer duration of AI compared to tamoxifen was associated with significantly improved DFS (HR 0.31; 95% CI 0.11-0.86; p = 0.025). While most pre-menopausal patients received adjuvant tamoxifen, the use of OFS and AIs increased significantly over time. The association between AI use and improved DFS may be consistent with prior randomized trials and warrants further investigation into predictive factors to guide treatment selection.

Predictors of Early Versus Late Recurrence in Invasive Lobular Carcinoma of the Breast: Impact of Local and Systemic Therapy

BACKGROUND

Invasive lobular carcinoma (ILC) of the breast is known for high risk of late recurrence, yet some patients still recur within 5 years of diagnosis. Determining factors associated with early/late recurrence could help tailor treatment and surveillance strategies.

METHODS

Using an institutional database, we evaluated patients with ILC and ≥ 5 years of follow-up or recurrence within 5 years. We used multivariate logistic regression and the Kaplan-Meier method to evaluate which clinicopathologic features and treatment strategies were associated with recurrence < 5 years since diagnosis versus recurrence ≥ 5 years since diagnosis. Additionally, we explored the association between Clinical Treatment Score 5 (CTS5) with early versus late recurrence.

RESULTS

Among 513 cases of stage I-III ILC, there were 75 early and 54 late recurrences during a median follow-up period of 9.4 years. Early recurrence was associated with larger tumors (mean 4.2 cm vs. 2.9 cm, p < 0.0001), higher incidence of > 3 positive nodes (32.4% vs. 9.11%, p > 0.0001), and more aggressive tumor biology (low/negative progesterone receptor expression, higher grade, and higher Ki67). Late recurrence was associated with younger age (mean 55.6 vs. 59.2 years, p = 0.037) and elevated body mass index (BMI > 25 kg/m2 in 60.1.0% vs. 45.4%, p = 0.021). Omission of adjuvant endocrine therapy or radiotherapy after lumpectomy conferred increased risk of early rather than late recurrence.

CONCLUSION

Factors related to tumor aggressiveness and treatment were associated with early recurrence, whereas patient related factors were related to late recurrence. These data may help guide treatment strategies and surveillance approaches for patients with ILC.

Erratum: 53 The development of a multi-institutional prospective registry for patients with metastatic invasive lobular carcinoma: identifying new markers of disease progression - CORRIGENDUM

[This corrects the article DOI: 10.1017/cts.2023.142.].

The impact of histologic subtype on primary site surgery in the management of metastatic lobular versus ductal breast cancer: a population based study from the National Cancer Database

Purpose

Primary site surgery for metastatic breast cancer improves local control but does not impact overall survival. Whether histologic subtype influences patient selection for surgery is unknown. Given differences in surgical management between early-stage lobular versus ductal disease, we evaluated the impact of histology on primary site surgery in patients with metastatic breast cancer.

Methods

The National Cancer Database (NCDB, 2010-2016) was queried for patients with stage IV HR-positive, HER2-negative invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC). We compared clinicopathologic features, primary site surgery rates, and outcomes by histologic subtype. Multivariable Cox proportional hazard models with and without propensity score matching were used for overall survival (OS) analyses.

Results

In 25,294 patients, primary site surgery was slightly but significantly less common in the 6,123 patients with ILC compared to the 19,171 patients with IDC (26.9% versus 28.8%, p = 0.004). Those with ILC were less likely to receive chemotherapy (41.3% versus 47.4%, p < 0.0001) or radiotherapy (29.1% versus 37.9%, p < 0.0001), and had shorter OS. While mastectomy rates were similar, those with ILC had more positive margins (10.6% versus 8.3%, p = 0.005). In both groups, the odds of undergoing surgery decreased over time, and were higher in younger patients with T2/T3 tumors and higher nodal burden.

Conclusion

Lobular histology is associated with less primary site surgery, higher positive margin rates, less radiotherapy and chemotherapy, and shorter OS compared to those with HR-positive HER2-negative IDC. These findings support the need for ILC-specific data and treatment approaches in the setting of metastatic disease.

HER-2 low status in early-stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series

PURPOSE

HER2 overexpression has a central role in breast cancer carcinogenesis and is associated with poor prognosis if untreated. Lately, identification of HER2-low breast cancer has been proposed to select patients for novel HER2-directed chemotherapy and includes cancers with immunohistochemistry 1 + or 2 + with negative FISH, encompassing approximately 55-60% of all breast carcinomas. In early-stage breast cancer, the prognostic significance of HER2 low-disease is less well understood, with a particular paucity of data evaluating the prevalence and implications of HER2-low status in invasive lobular carcinoma (ILC).

METHODS

We evaluated 666 stage I-III ILC tumors from a prospectively maintained institutional database, comparing clinicopathologic features and disease-free survival (DFS) using a multivariable Cox proportional hazards model.

RESULTS

HER2-low status was common in this cohort of patients with ILC, but most clinicopathologic features did not differ between HER2-low and HER2-negative cases. However, when adjusting for tumor size, number of positive nodes, ER/PR status, and local therapy received, patients with HER2-low status had worse disease-free survival (DFS) than those with HER2-negative tumors (hazard ratio 2.0, 95% confidence interval 1.0-4.1, p = 0.05).

CONCLUSION

This difference in DFS supports the notion that HER2-low and HER2-negative early stage ILC may differ clinically, despite similar clinicopathologic features. Further investigation into the potential benefit of HER2 targeted therapy in HER2-low early-stage breast cancer, and specifically lobular cancer, is warranted to ensure optimal outcomes in this distinct tumor subtype.

Abstract HER2-14: HER2-14 HER-2 low status in early stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series

Objectives: The concept of human epidermal growth factor receptor 2 (HER2)-low status has been proposed as a potential treatment target for breast cancers previously considered to be HER2-negative. Defined by an immunohistochemistry (IHC) score of 1+ or 2+ and negative fluorescent in situ hybridization (FISH) for HER2, HER2-low status predicts significant clinical benefit from novel therapeutic compounds in recent clinical trials. The prevalence and clinical implications of HER2-low status in patients with early stage invasive lobular carcinoma (ILC) has not been described. We aimed to describe the clinicopathologic features and prevalence of HER2-low status in ILC, and identify any potential differences in clinical outcome. Methods: We evaluated stage I-III ILC tumors from a prospectively maintained institutional database of patients where both IHC and FISH testing for HER2 status was performed as standard clinical care. Tumors were classified as HER2 negative (IHC=0), HER2-low (IHC=1+ or 2+ and negative FISH), or HER2 positive (IHC=3+ or FISH ratio ⇒2). Data were analyzed in Stata 16.1 using chi-squared tests, t-tests, and Cox proportional hazards models for disease free survival (DFS). Results: 666 ILC tumors with available HER2 status were available for analysis. The mean age at diagnosis was 59.8 years (range 21-91). The majority of patients had stage I disease (63.1%) with an average follow up time of 6.7 years (standard deviation [5.4]). Overall, 184 (27.6%) tumors were HER2 negative, 434 (65.1%) were HER2-low, and 48 (7.2%) were HER2 positive. There were no associations between HER2 status and age, menopausal status, body mass index, tumor stage, grade, presence of lymphovascular invasion, or molecular assay results. Hormone receptor status was significantly associated with HER2 status, with HER2 positive tumors significantly less likely to be estrogen receptor (ER) positive than both HER2 negative and HER2-low tumors (89.6% versus 97.3% and 96.8% respectively, p=0.03). HER2-low tumors were also significantly more likely to have progesterone receptor (PR) positivity (86.6% compared to 79.9% of HER2 negative and 72.9% of HER2 positive tumors, p = 0.01). This difference remained significant when comparing just HER2-low to HER2 negative cases (p=0.034). While there were no differences in use of neoadjuvant or adjuvant chemotherapy by HER2 status, HER2-low patients were significantly more likely to undergo mastectomy versus lumpectomy when compared to HER2 negative and HER2 positive patients (53.7% versus 38.0% and 43.8% respectively, p= 0.001). In a multivariable Cox proportional hazards model adjusting for tumor size, number of positive nodes, ER/PR status, and local therapy received, patients with HER2-low status had worse DFS than those with HER2 negative tumors (hazard ratio 2.0, 95% confidence interval 1.0 - 4.1, p=0.05). Conclusions: In this analysis of 666 early stage ILC cases, we found that most tumors were HER2-low, and that those with HER2-low disease were significantly more likely to have PR positive tumors and to undergo mastectomy. When adjusting for these variables, we identified a difference in DFS between HER2 negative and HER2-low early stage ILC. These findings support the contention that HER2-low and HER2 negative disease represent two different clinical entities. Further investigation of the potential benefit of HER2 targeted therapy in ILC, which predominately lacks HER2-amplified disease, is needed to ensure optimal outcomes in this understudied tumor type.

Citation Format: Harriet T. Rothschild, Elle Clelland, Anne Patterson, Julissa Molina-Vega, Mandeep Kaur, Mary Kathryn Abel, W. Fraser Symmans, Christopher J. Schwartz, Rita Mukhtar. HER2-14 HER-2 low status in early stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr HER2-14.

Abstract P2-03-16: Quantifying estrogen and progesterone receptor status in early-stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series

Background: Recent guidelines regarding estrogen (ER) and progesterone (PR) receptor testing from the American Society of Clinical Oncology and College of American Pathologists defined a new reporting category of ER-low positive breast cancer for tumors with 1-10% ER expression by immunohistochemistry (IHC). The clinical implications of ER-low positivity are incompletely understood, especially in invasive lobular carcinoma (ILC), the second most common type of breast cancer. Given the rarity of low-ER positivity in ILC, we evaluated tumor features and outcomes associated with a spectrum of ER/PR positivity in a monoinstitutional ILC cohort. Methods: We analyzed cases of stage I-III ILC with available IHC reports. Based on prior published categories in ILC, we classified ER as low, medium, or high as defined by ER staining of 10–69%, 70–89%, and ≥90% respectively. PR negative, low, and high tumors were defined by 0%, &lt; 20%, or ≥20% staining respectively. We used chi-squared tests, t-tests, and Cox proportional hazards models in Stata 16.1 to evaluate associations between ER/PR categories including clinicopathologic variables and event-free survival (EFS). Results: Of 744 cases, 24 (3.2%) were ER negative and 10 (1.3%) were ER-low positive as defined by 1-10% positive staining. 713 remaining cases had ER positivity ≥ 10% and comprised the cohort categories of ER low, medium, and high for this study (11.2%, 15.0%, and 73.8% respectively). In 751 cases with PR data, 122 (16.2%) were PR negative, 145 (19.4%) were PR low and 483 (64.3%) were PR high. ER high status was significantly associated with older age (mean 56.7, 56.7, and 60.6 years in ER low, medium, and high respectively, p=0.0005). ER low was associated with PR negative and low status (42.3% were PR neg/low and ER low, versus 37.4% with ER medium and 29.9% in ER high, p=0.045), and more likely to have overexpression of HER2 (9.7%, 9.0%, and 2.9% ER low, medium, high, respectively, p=0.002). ER low tumors were more likely to be grade 1 than ER medium or high (41.8%, 29.8% and 24.5% respectively, p=0.025), and have positive surgical margins (39.4%, 35.9% and 23.9% respectively, p=0.002). ER status was not associated with Ki67, stage, body mass index (BMI), lymphovascular invasion, lobular carcinoma in situ (LCIS), pleomorphic histology, local therapy, or chemotherapy use. In contrast, PR high was significantly associated with younger age (57.6 versus 63.5 years in PR low, p&lt; 0.0001). PR low was associated with HER2 overexpression (8.6% versus 3.2% in PR high, p=0.002). PR low cases were more likely to present at higher stages (15.8% stage III versus 10.1% stage III in PR high, p=0.032), to be pleomorphic (16.8% versus 8.2%, p&lt; 0.001), and to receive chemotherapy (30.8% versus 23.1%, p=0.022) but were less likely to have associated LCIS (64.0 versus 74.2%, p=0.004). PR status was not associated with Ki67, BMI, lymphovascular invasion, local therapy, or surgical margins. In a Cox proportional hazards model adjusting for age, stage, grade, pleomorphic histology, and chemotherapy use, ER category was not associated with EFS but both PR negative and PR low status each had significantly worse EFS compared to PR ≥20% (HR 3.5, 95% CI 1.8-6.7, p&lt; 0.001 for PR negative, and HR 2.0, 95% CI 1.1-3.5, p=0.015 for PR low). The estimated cumulative 5-year EFS for patients with ER low, medium, and high tumors was 87.1%, 93.4%, and 90.1% respectively. The estimated cumulative 5-year EFS for patients with PR negative, low, and high tumors was 78.9%, 90.2%, and 92.7% respectively. Conclusions: Using ILC-specific categories for ER expression, we found associations between ER category and clinicopathologic variables but not with EFS. In contrast, PR negative and low status was associated with worse EFS. These findings highlight the importance of exploring the spectrum of ER/PR activity within ILC, a classically strongly hormone receptor-positive tumor type, using more quantitative methods.

Citation Format: Elle Clelland, Harriet T. Rothschild, Anne Patterson, Julissa Molina-Vega, Mandeep Kaur, Mary Kathryn Abel, W. Fraser Symmans, Jo Chien, Christopher J. Schwartz, Rita Mukhtar. Quantifying estrogen and progesterone receptor status in early-stage invasive lobular carcinoma of the breast: associated factors and outcomes in an institutional series [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-03-16.

Obesity and menopausal status impact the features and molecular phenotype of invasive lobular breast cancer

Purpose

We investigated the relationship between obesity, menopausal status, and invasive lobular carcinoma (ILC), the second most common histological subtype of breast cancer. Specifically, we evaluated the association between body mass index (BMI), metabolic syndrome, the 21-gene Oncotype Recurrence Score (Oncotype RS), and pathological features in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor-2-negative ILC.

Methods

The study cohort included 491 patients from a prospectively maintained institutional database consisting of patients with stage I-III, HR-positive ILC who underwent surgical treatment between 1996 and 2019.

Results

Contrary to our expectations, we found that lower BMI was significantly associated with having higher Oncotype RS (18.9% versus 4.8%, p = 0.028) in post-menopausal patients, but was not related to tumor characteristics in pre-menopausal patients. Multivariate network analyses suggested a strong relationship between post-menopausal status itself and tumor characteristics, with lesser influence of BMI.

Conclusion

These findings provide further insight into the recently appreciated heterogeneity within ILC and support the need for further investigation into the drivers of this disease and tailored treatment strategies.

Modulation of the immune microenvironment of high-risk ductal carcinoma in situ by intralesional pembrolizumab injection

Ductal carcinoma in situ (DCIS) is a risk factor for the subsequent development of invasive breast cancer. High-risk features include age <45 years, size >5 cm, high-grade, palpable mass, hormone receptor negativity, and HER2 positivity. We have previously shown that immune infiltrates are positively associated with these high-risk features, suggesting that manipulating the immune microenvironment in high-risk DCIS could potentially alter disease progression. Patients with high-risk DCIS were enrolled in this 3 × 3 phase 1 dose-escalation pilot study of 2, 4, and 8 mg intralesional injections of the PD-1 immune checkpoint inhibitor, pembrolizumab. Study participants received two intralesional injections, three weeks apart, prior to surgery. Tissue from pre-treatment biopsies and post-treatment surgical resections was analyzed using multiplex immunofluorescence (mIF) staining for various immune cell populations. The intralesional injections were easily administered and well-tolerated. mIF analyses demonstrated significant increases in total T cell and CD8+ T cell percentages in most patients after receiving pembrolizumab, even at the 2 mg dose. T cell expansion was confined primarily to the stroma rather than within DCIS-containing ducts. Neither cleaved caspase 3 (CC3) staining, a marker for apoptosis, nor DCIS volume (as measured by MRI) changed significantly following treatment. Intralesional injection of pembrolizumab is safe and feasible in patients with DCIS. Nearly all patients experienced robust total and CD8+ T cell responses. However, we did not observe evidence of cell death or tumor volume decrease by MRI, suggesting that additional strategies may be needed to elicit stronger anti-tumor immunity.