Abstract OT3-25-01: Neoadjuvant HER2-targeted Therapy +/- Immunotherapy with Pembrolizumab (neoHIP): An Open Label Randomized Phase II Trial

Background: Immune checkpoint inhibition (ICI) is synergistic with HER2-directed therapy in pre-clinical models. Clinically, pembrolizumab (K)-mediated ICI plus HER2-directed therapy with trastuzumab (H) was safe and demonstrated modest activity in H-resistant HER2-positive (HER2+) metastatic breast cancer. Because ICI may confer more robust activity when administered earlier in the course of disease, H and K administered in the curative-intent, treatment-naive setting may allow for de-escalation of cytotoxic chemotherapy; confer life-long, tumor-specific immunity; and ultimately, improve cure rates. Moreover, the synergy of H and K with paclitaxel (T) may overcome the need for dual HER2-blockade with H plus pertuzumab (P). In this randomized, multicenter, phase II, open-label, multi-center trial the efficacy and safety of neoadjuvant THP vs THP-K vs TH-K are explored. Methods: 174 patients (pts) ≥18y with previously untreated, stage II-III, HER2+ breast cancer will be randomized and stratified by clinical nodal status (positive vs. negative) and hormone receptor status (positive vs. negative). In arm A, pts receive T at 80mg/m2 weekly for 12 weeks, H at 8mg/Kg (loading dose) and then 6mg/Kg every 3 weeks x 3 doses, P at 840 mg (loading dose) and then 420mg/Kg every 3 weeks x 3 doses (THP). In arm B, pts receive THP plus K at 200mg every 3 weeks x 4 doses (THP-K). In arm C, pts receive TH-K; however, in a preplanned interim analysis, arm C did not meet the pre-defined efficacy threshold and this arm was subsequently closed. Enrollment to arms A and B continue. Definitive surgery is 3-6 weeks after the last dose. After surgery, pts are treated per the treating physician’s discretion including radiotherapy per local clinical standard. Pts whose tumors are hormone-receptor positive will receive hormone therapy per local standard-of-care. The primary end point is pathologic complete response (pCR) rate in the breast and axilla (ypT0/Tis ypN0). Secondary end points include pCR rate by ypT0ypN0 and ypT0/Tis, residual cancer burden index, event free survival, breast conserving surgery rate, safety and overall survival. Exploratory correlative studies will characterize potential immune biomarkers predictive of efficacy and/or toxicity. Funding sources: BCRF, Merck NCT03747120

Citation Format: Heather McArthur, Jorge Henrique Santos Leal, Christina DiLauro Abaya, Sangeetha Reddy, Meredith Carter, Reva Basho, Michelle Phillips, David Chan, Hugo Hool, Dorothy Park, Mary El-Masry, Philomena McAndrew, Swati Sikaria, Laura M. Spring, Aditya Bardia, Mourad Tighiouart, Farnaz Dadmanesh, Armando Giuliano, Stephen Shiao, David B. Page. Neoadjuvant HER2-targeted Therapy +/- Immunotherapy with Pembrolizumab (neoHIP): An Open Label Randomized Phase II Trial [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 OT3-25-01.

Abstract OT1-19-01: A Single Arm Phase 2 Study of Peri-Operative Checkpoint-Mediated Immune Therapy and Cryoablation in Women with Hormone Receptor-Negative, HER2-Negative Early Stage/Resectable Breast Cancer

Background: Local tumor destruction with cryoablation (cryo) induces inflammation and releases antigens that can activate tumor-specific immune responses. Pre-clinically, cryo with immune checkpoint inhibition (ICI)-augmented tumor-specific immune responses and prevented recurrence. Clinically, we established that peri-operative (peri-op) cryo with ipilimumab (ipi) +/- nivolumab (nivo) was not only safe in patients (pts) with operable, early stage breast cancer (ESBC) but also generated robust intra-tumoral and systemic immune responses. In this phase 2 study, we evaluate the disease specific impact of peri-op ICI in women with residual triple negative breast cancer (TNBC) after neoadjuvant chemotherapy (NAC), a subset at high risk of early relapse. Methods: Eligible pts are ≥18y, with ER < 10%, PR < 10%, HER2 negative (per ASCO/CAP definition), ≥ 1.0 cm, residual operable disease after taxane-based NAC. Approximately 80 pts will be enrolled and treated with ipi/nivo/cryo followed by breast surgery and adjuvant nivo across multiple institutions. Pts undergo percutaneous, image-guided cryo with concurrent research core biopsy 7-10 days prior to surgery and will receive ipi (1mg/kg IV) with nivo (240mg IV) 1 to 5 days prior to cryo. After surgery, pts will receive 3 additional doses of nivo at 240mg IV Q2 weeks. Adjuvant capecitabine is recommended for all patients per local standard-of-care. Patients will be stratified by NAC platinum administration, NAC anthracycline administration, and clinical nodal status (positive versus negative). The primary endpoint is 3-year Event Free Survival (EFS). Secondary endpoints include Invasive Disease-Free Survival (IDFS), Distant Disease-Free Survival (DDFS), overall survival (OS) and safety. Exploratory correlative studies will be performed on tumor and serum to characterize the immunologic impact of the intervention and to explore predictors of efficacy and toxicity. Funding sources: Susan G. Komen, ASCO Conquer Cancer Foundation, Breast Cancer Research Foundation, Bristol-Myers Squibb, BTG International Ltd. NCT03546686

Citation Format: Heather McArthur, Elizabeth Comen, Yolanda Bryce, Stephen Solomon, Jorge Henrique Santos Leal, Christina DiLauro Abaya, Cristal Martinez, Reva Basho, Dorothy Park, Philomena McAndrew, Brigid Larkin, William Mills, David B. Page, Staci Mellinger, Nicole Fredrich, Nicole Moxon, Sangeetha Reddy, Meredith Carter, Sujata Patil, Larry Norton. A Single Arm Phase 2 Study of Peri-Operative Checkpoint-Mediated Immune Therapy and Cryoablation in Women with Hormone Receptor-Negative, HER2-Negative Early Stage/Resectable Breast Cancer [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 OT1-19-01.

A single-arm, phase 2 study of perioperative ipilimumab, nivolumab, and cryoablation in women with hormone receptor-negative, HER2-negative, early-stage/resectable breast cancer

TPS617

Background: Local tumor destruction with cryoablation (cryo) induces inflammation and releases antigens that can activate tumor-specific immune responses. Pre-clinically, cryo with checkpoint inhibition augmented tumor-specific immune responses and prevented recurrence. Clinically, we established that peri-operative (peri-op) cryo with ipilimumab (ipi) +/- nivolumab (nivo) was not only safe in patients (pts) with operable, early stage breast cancer (ESBC) but also generated robust intra-tumoral and systemic immune responses. In this phase 2 study, we evaluate the disease specific impact of peri-op ipi/nivo/cryo in women with residual triple negative breast cancer (TNBC) after neoadjuvant chemotherapy (NAC), a subset at high risk of early relapse. Methods: Eligible pts are ≥18y, with ER < 10%, PR < 10%, HER2 negative (per ASCO/CAP definition), ≥ 1.0 cm, residual operable disease after taxane-based NAC. Approximately 80 pts will be enrolled and treated with ipi/nivo/cryo followed by breast surgery and adjuvant nivo. Pts undergo percutaneous, image-guided cryo with concurrent research core biopsy 7-10 days prior to surgery and will receive ipi (1mg/kg IV) with nivo (240mg IV) 1 to 5 days prior to cryo. After surgery, pts will receive 3 additional doses of nivo at 240mg IV Q2 weeks. Adjuvant capecitabine is recommended for all patients per local standard-of-care. Patients will be stratified by NAC platinum administration, NAC anthracycline administration, and clinical nodal status (positive versus negative). The primary endpoint is 3-year Event Free Survival (EFS). Secondary endpoints include Invasive Disease-Free Survival (IDFS), Distant Disease-Free Survival (DDFS), overall survival (OS) and safety. Exploratory correlative studies will be performed on tumor and serum to characterize the immunologic impact of the intervention and to explore predictors of efficacy and toxicity. Clinical trial information: NCT03546686.

Neoadjuvant HER2-targeted therapy +/- immunotherapy with pembrolizumab (neoHIP): An open-label randomized phase II trial

TPS624

Background: Immune checkpoint inhibition (ICI) is synergistic with HER2-directed therapy in pre-clinical models. Clinically, pembrolizumab (K)-mediated ICI plus HER2-directed therapy with trastuzumab (H) was safe and demonstrated modest activity in H-resistant HER2-positive (HER2+) metastatic breast cancer. Because ICI may confer more robust activity when administered earlier in the course of disease, H and K administered in the curative-intent, treatment-naive setting may allow for de-escalation of cytotoxics; confer life-long, tumor-specific immunity; and ultimately, improve cure rates. Moreover, the synergy of H and K with paclitaxel (T) may overcome the need for dual HER2-blockade with H plus pertuzumab (P). In this randomized, multicenter, phase II, open-label trial the efficacy and safety of neoadjuvant THP vs THP-K vs TH-K are explored. Methods: 174 patients (pts) ≥18y with previously untreated, stage II-III, HER2+ breast cancer will be randomized and stratified by clinical nodal status (positive vs. negative) and hormone receptor status (positive vs. negative). In arm A, pts receive T at 80mg/m2 weekly for 12 weeks, H at 8mg/Kg (loading dose) and then 6mg/Kg every 3 weeks x 3 doses, P at 840 mg (loading dose) and then 420mg/Kg every 3 weeks x 3 doses (THP). In arm B, pts receive THP plus K at 200mg every 3 weeks x 4 doses (THP-K). In arm C, pts receive TH-K. Definitive surgery is 3-6 weeks after the last dose. After surgery, pts are treated per the treating physician’s discretion including radiotherapy per local clinical standard. Pts whose tumors are hormone-receptor positive will receive hormone therapy per local standard-of-care. The primary end point is pathologic complete response (pCR) rate in the breast and axilla (ypT0/Tis ypN0). Secondary end points include pCR rate by ypT0ypN0 and ypT0/Tis, residual cancer burden index, event free survival, breast conserving surgery rate, safety and overall survival. Exploratory correlative studies will characterize potential immune biomarkers predictive of efficacy and/or toxicity. Clinical trial information: NCT03747120.

Abstract PS12-09: Pre-operative pembrolizumab (Pembro) with radiation therapy (RT) in patients with operable triple-negative breast cancer (TNBC)

Background: Pembrolizumab (pembro)-mediated checkpoint blockade has shown only modest efficacy in triple negative breast cancer (TNBC). Pathologic complete response (pCR) rates in TNBC are 34-55% with neoadjuvant chemotherapy and 26% with neoadjuvant stereotactic radiation therapy (RT) alone. However, because RT induces immune-mediated cell death that can generate a rich supply of tumor antigens and trigger anti-tumor immunity, the addition of pembro to RT can generate robust anti-tumor immune responses as demonstrated in metastatic TNBC. If administered in the pre-operative setting, immune therapy plus RT could induce long-term tumor-specific memory, and ultimately, improve cure rates. This study aimed to establish the safety of pre-operative pembro plus RT in 20 TNBC patients for whom lumpectomy and adjuvant RT were planned and to explore predictive biomarkers (NCT03366844).

Methods: Women planning breast conserving surgery for operable, stage II/III, TNBC were enrolled in this single-institution pilot study. Study treatment consisted of pre-operative pembro (200mg IV) followed 3 weeks later by pembro (200mg IV) plus RT (24 Gy/3 fractions) to the primary breast tumor followed 3-5 weeks later by standard-of-care (SOC) neoadjuvant chemotherapy. Adjuvant RT was administered per SOC after surgery, but without a boost dose. Research blood and tumor biopsies were obtained at baseline, at week 4 prior to pembro/RT, and at week 6-8 prior to chemotherapy initiation. Co-primary endpoints were: safety/tolerability (defined by the number of patients who do not necessitate a delay in SOC chemotherapy or surgery) and change in tumor infiltrating lymphocyte (TIL) score. Secondary endpoints include safety/toxicity up to 19 weeks after study enrollment and pathologic complete response (pCR) rate.

Results: 20 patients were enrolled and completed all treatment (pembro, RT, chemotherapy and surgery) as of July 2020. The median age is 55y (range 33-70y). The stage distribution is IIA (11), IIB (6), IIIA (2) and IIIC (1) with biopsy proven nodal involvement in 55%. All patients received a taxane containing regimen, 12/20 (60%) received carboplatin and 15/20 (75%) received an anthracycline. Three patients did not complete the planned course of chemotherapy, two of whom had residual disease. None of the patients experienced significant delay (&gt;2 weeks) in receiving SOC treatment. There were no observed grade 3 or 4 toxicities observed during the pembro +/- RT treatment. Grade 4 colitis in 2/20 was reported during SOC chemotherapy and was attributed to pembro. The most frequent grade 1/2 toxicities were nausea (4/20), arthralgia (15/20), fatigue (16/20), maculopapular rash (1/20), diarrhea (1/20) and mucositis (1/20). At the time of surgery, 12/20 (60%) were ypT0N0 and 13/20 (65%) were ypT0/Tis. 15/20 (75%) achieved an RCB 0/1, 4/20 (20%) were RCB 2 and 1/20 (5%) was RCB 3. Of the 11 patients with node-positive disease at diagnosis, 9/11 (82%) became ypN0, 1/11 (9%) became ypN1mic and 1/11 (9%) became ypN1a. No patients progressed during treatment. Change in TILs after pembro or pembro-RT did not correlate with treatment response, however baseline TIL count ≥10% in the initial biopsy was associated with pCR (p = 0.005). Further profiling of the immune cells in the biopsies revealed that RCB 0/1 patients were strongly associated with increased numbers of CD8+ T cells and lower numbers of CD11b+ myeloid cells following the combination of pembro and RT.

Conclusions: Neoadjuvant pembro plus RT prior to SOC chemotherapy is safe/feasible and may increase pCR rates and clearance of nodal metastases beyond chemotherapy alone. A phase 2 study of checkpoint blockade + RT expansion of this trial (n=50) is currently accruing.

Citation Format: Heather McArthur, Stephen Shiao, Scott Karlan, Reva Basho, Farin Amersi, Brittany Arnold, Michele Burnison, Alice Chung, Cathie Chung, Catherine Dang, Armando Giuliano, Nimmi Kapoor, Negin Habibi Khameneh, Simon Knott, Cynthia Martin, Philomena McAndrew, Monica Mita, Dorothy Park, Christina DiLauro Abaya, Alice Ho. Pre-operative pembrolizumab (Pembro) with radiation therapy (RT) in patients with operable triple-negative breast cancer (TNBC) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS12-09.

Abstract OT2-04-04: Neoadjuvant HER2-targeted therapy +/- immunotherapy with pembrolizumab (neoHIP): An open label randomized phase 2 trial

Background: Immune checkpoint inhibition (ICI) is synergistic with HER2-directed therapy in pre-clinical models. Clinically, pembrolizumab (K)-mediated ICI plus HER2-directed therapy with trastuzumab (H) was safe and demonstrated modest activity in H-resistant HER2-positive (HER2+) metastatic breast cancer. Because ICI may confer more robust activity when administered earlier in the course of disease, HER2-directed therapy with ICI administered in the curative-intent, treatment-naive setting may allow for de-escalation of cytotoxic backbones; confer life-long, tumor-specific immunity; and ultimately, improve cure rates. Moreover, the synergy of H and K with paclitaxel (T) may overcome the need for dual HER2-blockade with H plus pertuzumab (P). In this randomized, multicenter, phase II, open-label trial, the efficacy and safety of neoadjuvant THP vs THP-K vs TH-K are being explored (NCT03747120). Methods: 174 patients (pts) ≥18years with previously untreated, clinical stage II-III, HER2+ breast cancer will be randomized 1:1:1 to one of 3 study arms, stratified by clinical nodal status (positive vs. negative) and hormone receptor status (positive vs. negative). In arm A, pts receive THP: T at 80 mg/m2 weekly for 12 weeks, H day 1 at 8 mg/Kg (loading dose) and then 6 mg/Kg every 3 weeks x 3 doses, P day 1 at 840 mg (loading dose) and then 420 mg/Kg every 3 weeks x 3 doses (THP). In arm B, pts receive THP plus K day 1 at 200mg (flat dose) and then every 3 weeks x 3 doses (THP-K). In arm C, pts receive TH-K. Definitive surgery is 3-6 weeks after the last dose of T. After surgery, pts are treated per the treating physician’s discretion including HER2-directed therapy, endocrine therapy and radiotherapy per local clinical standards. The primary endpoint is pathologic complete response (pCR) rate in the breast and axilla (ypT0/Tis ypN0). Secondary end points include pCR rate by ypT0ypN0 and ypT0/Tis, residual cancer burden index, event free survival, breast conserving surgery rate, safety and overall survival. Exploratory correlative studies will characterize potential immune biomarkers predictive of efficacy and/or toxicity.

Citation Format: Heather McArthur, Jorge Leal, David Page, Christina DiLauro Abaya, Reva Basho, Lindsey Ristow, Hannah Coleman, Stephen Shiao, Simon Knott, Monica Mita, Mourad Tighiouart, Alice Chung, Farnaz Dadmanesh, Philomena McAndrew, Scott Karlan, Sunil Verma, Armando Giuliano. Neoadjuvant HER2-targeted therapy +/- immunotherapy with pembrolizumab (neoHIP): An open label randomized phase 2 trial [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 OT2-04-04.

Abstract OT1-01-04: A randomized phase 2 study of peri-operative ipilimumab, nivolumab and cryoablation versus standard care in women with residual, early stage/resectable, triple negative breast cancer after standard-of-care neoadjuvant chemotherapy

Background: Local tumor destruction with cryoablation (cryo) induces inflammation and releases antigens that can activate tumor-specific immune responses. Pre-clinically, cryo with checkpoint inhibition augmented tumor-specific immune responses and prevented recurrence. Clinically, we established that peri-operative (peri-op) cryo with ipilimumab (ipi) +/- nivolumab (nivo) was not only safe in patients (pts) with operable, early stage breast cancer (ESBC) but also generated robust intra-tumoral and systemic immune responses. In this randomized phase 2 study, we evaluate the disease specific impact of peri-op ipi/nivo/cryo versus standard care in women with residual triple negative breast cancer (TNBC) after neoadjuvant chemotherapy (NAC), a subset at high risk of early relapse.

Methods: Eligible pts are ≥18y, with ER &lt;10%, PR &lt;10%, HER2 negative (per ASCO/CAP definition), ≥ 1.0 cm, residual operable disease after taxane-based NAC. Approximately 160 pts will be randomized to one of two arms: breast surgery (control arm) or ipi/nivo/cryo followed by breast surgery and adjuvant nivo (intervention arm). Pts in the intervention arm will undergo percutaneous, image-guided cryo with concurrent research core biopsy 7-10 days prior to surgery and will receive ipi (1mg/kg IV) with nivo (240mg IV) 1 to 5 days prior to cryo. After surgery, pts will receive 3 additional doses of nivo at 240mg IV Q2 weeks. Adjuvant capecitabine is recommended for all patients per local standard-of-care. Patients will be stratified by NAC platinum administration, NAC anthracycline administration, and clinical nodal status (positive versus negative). The primary endpoint is 3-year Event Free Survival (EFS). Secondary endpoints include Invasive Disease-Free Survival (IDFS), Distant Disease-Free Survival (DDFS), overall survival (OS) and safety. Exploratory correlative studies will be performed on tumor and serum to characterize the immunologic impact of the intervention and to explore predictors of efficacy and toxicity.

Citation Format: Heather McArthur, Elizabeth Comen, Yolanda Bryce, Stephen B Solomon, Jorge Leal, Micaela Rodine, Christina DiLauro Abaya, Sujita Patil, David Page, Larry Norton. A randomized phase 2 study of peri-operative ipilimumab, nivolumab and cryoablation versus standard care in women with residual, early stage/resectable, triple negative breast cancer after standard-of-care neoadjuvant chemotherapy [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 OT1-01-04.

Pembrolizumab (pembro) with paclitaxel (taxol) or capecitabine (cape) as early treatment of metastatic triple-negative breast cancer (mTNBC)

1015

Background: Atezolizumab (anti-PD-L1) plus nab-paclitaxel was shown to improve outcomes in mTBNC in a phase III clinical trial. Subjects were required to be > 12 months from curative-intent therapy in this trial. It remains unknown whether non-taxane chemo + anti-PD-1/L1 will be beneficial in mTNBC, or whether this approach is effective in rapidly-progressing patients ( < 12 mo from curative-intent therapy). Methods: mTNBC patients were enrolled in a phase Ib study of anti-PD-1 (pembro, 200mg IV q3w) plus physician’s choice chemo (cape: n = 14, 2000mg BID, 7d on/7d off; or taxol: n = 14, 80mg/m2 q1w). Primary/secondary objectives were to evaluate safety/tolerability (primary) and RECIST1.1 response (w12). The exploratory objective was to explore for differences in immunomodulation according to chemo choice. Mixed effects models were employed to compare the longitudinal effects of chemo on peripheral immune cells (flow cytometry) and T-cell diversity (Immunoseq assay). Results: Enrollment of the trial is complete (n = 28), with 100% of evaluable patients tolerating therapy (n = 22) as of 2/1/2019. Cape ORR was 43% (5 PR, 1 CR, 2 SD) with median PFS = 155d. Taxol ORR was 25% (1 CR, 1 PR, 3 SD) with median PFS = 99d. Subjects enrolled < 12 months from curative-intent therapy had numerically lower response (ORR = 27%, 1 CR, 2 PR, 3 SD) than subjects without rapid progression (ORR = 45%, 1 CR, 4 PR, 2 SD). No significant differences in immunomodulation were observed according to chemo type, however both cape & taxol were associated with declines in T-cell quantity (CD4 p < .02, CD8 p < .04) and Immunoseq T-cell fraction over time. Conclusions: Pembro plus cape or taxol is safe with encouraging efficacy, however activity may be lower in the setting of rapid progression following curative-intent chemo. Cape+pembro efficacy is favorable with no measurable differences in immunomodulation, and therefore cape may be preferred as a chemo backbone in selected patients. Both cape and taxol are associated with iatrogenic declines in T-cell quantity, which may explain the observed dropoff in anti-PD-1/L1 activity in later lines. Clinical trial information: NCT02734290.

Preoperative checkpoint inhibition (CPI) and cryoablation (Cryo) in women with early-stage breast cancer (ESBC)

592

Background: Checkpoint inhibition (CPI) combined with local strategies that cause local tumor destruction, such as cryo may augment tumor specific immunity and improve survival. We previously demonstrated in 18 ESBC patients (pts) that pre-operative (pre-op) cryo with ipilimumab (ipi) is not only safe but also generates robust local and systemic immune responses (NCT01502592). Given the added activity of dual CPI in other tumors, we undertook a second pilot study of pre-op ipi/nivolumab (nivo)/cryo to confirm the safety of this combination and the impact on immune biomarkers. Methods: In both pilot studies, eligible pts had operable ≥1.5cm invasive HER2 negative ESBC. CPI was administered 8-15d prior to, and cryo was performed 7-10d prior to, standard-of-care (SOC) surgery. Toxicity evaluation continued for 12wks after drug administration. Blood for immune correlates was obtained at baseline, cryo, surgery and 2-4 weeks thereafter. Tumor samples were obtained at cryo and surgery. Flow-cytometry of peripheral lymphocytes was compared to previously reported ipi/cryo responses. Results: After a median follow-up of 66 months all 18 ESBC ipi/cryo pts, including 3 TNBC pts, are recurrence free. In the ipi/nivo/cryo study, the safety primary endpoint was met when 5 pts underwent SOC surgery without delay. Ipi/nivo/cryo was well tolerated overall. One pt on an aromatase inhibitor had grade 4 liver toxicity 8 weeks after surgery. One pt, 3 weeks after her SOC surgery, developed grade 1 hyperthyroidism, preventing a secondary axillary dissection from proceeding as scheduled. Robust activation of peripheral CD4+ and CD8+ T cells peaked at week 2 post ipi/nivo with the majority of activated CD8+ T cells expressing PD1. Comparing the correlatives of the ipi/nivo/cryo study with the prior ipi/cryo study, we observed higher expression of activation markers (Ki-67, ICOS, CTLA-4, LAG-3) on peripheral T cells and downregulation of suppressor cells. Conclusions: Ipi/cryo-treated pts, including 3 TNBC pts, remain recurrence free after > 5y. Combining cryo with ipi/nivo preop is feasible, safe, and associated with greater T cell activation than ipi/cryo alone. These results informed an ongoing randomized phase 2 study of pre-op ipi/nivo/cryo versus SOC in women with residual TNBC after neoadjuvant chemotherapy (NCT03546686). Clinical trial information: NCT02833233.