Explore the vast range of titles available.

Docetaxel-based chemotherapy is effective in metastatic gastric and gastro-oesophageal junction adenocarcinoma. This study reports on the safety and efficacy of the docetaxel-based triplet FLOT (fluorouracil plus leucovorin, oxaliplatin and docetaxel) as a perioperative therapy for patients with locally advanced, resectable tumours. In this controlled, open-label, phase 2/3 trial, we randomly assigned 716 patients with histologically-confirmed advanced clinical stage cT2 or higher or nodal positive stage (cN+), or both, resectable tumours, with no evidence of distant metastases, via central interactive web-based-response system, to receive either three pre-operative and three postoperative 3-week cycles of 50 mg/m2 epirubicin and 60 mg/m2 cisplatin on day 1 plus either 200 mg/m2 fluorouracil as continuous intravenous infusion or 1250 mg/m2 capecitabine orally on days 1 to 21 (ECF/ECX; control group) or four preoperative and four postoperative 2-week cycles of 50 mg/m2 docetaxel, 85 mg/m2 oxaliplatin, 200 mg/m2 leucovorin and 2600 mg/m2 fluorouracil as 24-h infusion on day 1 (FLOT; experimental group). The primary outcome of the trial was overall survival (superiority) analysed in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT01216644. Between Aug 8, 2010, and Feb 10, 2015, 716 patients were randomly assigned to treatment in 38 German hospitals or with practice-based oncologists. 360 patients were assigned to ECF/ECX and 356 patients to FLOT. Overall survival was increased in the FLOT group compared with the ECF/ECX group (hazard ratio [HR] 0·77; 95% confidence interval [CI; 0.63 to 0·94]; median overall survival, 50 months [38·33 to not reached] vs 35 months [27·35 to 46·26]). The number of patients with related serious adverse events (including those occurring during hospital stay for surgery) was similar in the two groups (96 [27%] in the ECF/ECX group vs 97 [27%] in the FLOT group), as was the number of toxic deaths (two [<1%] in both groups). Hospitalisation for toxicity occurred in 94 patients (26%) in the ECF/ECX group and 89 patients (25%) in the FLOT group. In locally advanced, resectable gastric or gastro-oesophageal junction adenocarcinoma, perioperative FLOT improved overall survival compared with perioperative ECF/ECX. The German Cancer Aid (Deutsche Krebshilfe), Sanofi-Aventis, Chugai, and Stiftung Leben mit Krebs Foundation.

The best multimodal approach for resectable locally advanced esophageal adenocarcinoma is unclear. An important question is whether perioperative chemotherapy is preferable to preoperative chemoradiotherapy. In this phase 3, multicenter, randomized trial, we assigned in a 1:1 ratio patients with resectable esophageal adenocarcinoma to receive perioperative chemotherapy with FLOT (fluorouracil, leucovorin, oxaliplatin, and docetaxel) plus surgery or preoperative chemoradiotherapy (radiotherapy at a dose of 41.4 Gy and carboplatin and paclitaxel) plus surgery. Eligibility criteria included a primary tumor with a clinical stage of cT1 cN+, cT2-4a cN+, or cT2-4a cN0 disease, in which T indicates the size and extent of the tumor (higher numbers indicate a more advanced tumor), and N indicates the presence (N+) or absence (N0) of cancer spread to the lymph nodes, without evidence of metastatic spread. The primary end point was overall survival. From February 2016 through April 2020, we assigned 221 patients to the FLOT group and 217 patients to the preoperative-chemoradiotherapy group. With a median follow-up of 55 months, overall survival at 3 years was 57.4% (95% confidence interval [CI], 50.1 to 64.0) in the FLOT group and 50.7% (95% CI, 43.5 to 57.5) in the preoperative-chemoradiotherapy group (hazard ratio for death, 0.70; 95% CI, 0.53 to 0.92; P = 0.01). Progression-free survival at 3 years was 51.6% (95% CI, 44.3 to 58.4) in the FLOT group and 35.0% (95% CI, 28.4 to 41.7) in the preoperative-chemoradiotherapy group (hazard ratio for disease progression or death, 0.66; 95% CI, 0.51 to 0.85). Among the patients who started the assigned treatment, grade 3 or higher adverse events were observed in 120 of 207 patients (58.0%) in the FLOT group and in 98 of 196 patients (50.0%) in the preoperative-chemoradiotherapy group. Serious adverse events were observed in 98 of 207 patients (47.3%) in the FLOT group and in 82 of 196 patients (41.8%) in the preoperative-chemoradiotherapy group. Mortality at 90 days after surgery was 3.1% in the FLOT group and 5.6% in the preoperative-chemoradiotherapy group. Perioperative chemotherapy with FLOT led to improved survival among patients with resectable esophageal adenocarcinoma as compared with preoperative chemoradiotherapy. (Funded by the German Research Foundation; ESOPEC ClinicalTrials.gov number, NCT02509286.).

In resectable gastric and gastroesophageal junction cancer, adding durvalumab to perioperative chemotherapy improved event-free survival and pathological complete response, with no major increase in high-grade adverse events.

There are few effective treatment options for patients with recurrent or metastatic head-and-neck squamous cell carcinoma. Pembrolizumab showed antitumour activity and manageable toxicity in early-phase trials. We aimed to compare the efficacy and safety of pembrolizumab versus standard-of-care therapy for the treatment of head-and-neck squamous cell carcinoma. We did a randomised, open-label, phase 3 study at 97 medical centres in 20 countries. Patients with head-and-neck squamous cell carcinoma that progressed during or after platinum-containing treatment for recurrent or metastatic disease (or both), or whose disease recurred or progressed within 3–6 months of previous multimodal therapy containing platinum for locally advanced disease, were randomly assigned (1:1) in blocks of four per stratum with an interactive voice-response and integrated web-response system to receive pembrolizumab 200 mg every 3 weeks intravenously or investigator's choice of standard doses of methotrexate, docetaxel, or cetuximab intravenously (standard-of-care group). The primary endpoint was overall survival in the intention-to-treat population. Safety was analysed in the as-treated population. This trial is registered with ClinicalTrials.gov, number NCT02252042, and is no longer enrolling patients. Between Dec 24, 2014, and May 13, 2016, 247 patients were randomly allocated to pembrolizumab and 248 were randomly allocated to standard of care. As of May 15, 2017, 181 (73%) of 247 patients in the pembrolizumab group and 207 (83%) of 248 patients in the standard-of-care group had died. Median overall survival in the intention-to-treat population was 8·4 months (95% CI 6·4–9·4) with pembrolizumab and 6·9 months (5·9–8·0) with standard of care (hazard ratio 0·80, 0·65–0·98; nominal p=0·0161). Fewer patients treated with pembrolizumab than with standard of care had grade 3 or worse treatment-related adverse events (33 [13%] of 246 vs 85 [36%] of 234). The most common treatment-related adverse event was hypothyroidism with pembrolizumab (in 33 [13%] patients) and fatigue with standard of care (in 43 [18%]). Treatment-related death occurred in four patients treated with pembrolizumab (unspecified cause, large intestine perforation, malignant neoplasm progression, and Stevens-Johnson syndrome) and two patients treated with standard of care (malignant neoplasm progression and pneumonia). The clinically meaningful prolongation of overall survival and favourable safety profile of pembrolizumab in patients with recurrent or metastatic head and neck squamous cell carcinoma support the further evaluation of pembrolizumab as a monotherapy and as part of combination therapy in earlier stages of disease. Merck Sharp & Dohme, a subsidiary of Merck & Co.

Neoadjuvant therapy is the standard treatment for patients with locally advanced oesophageal squamous cell carcinoma (OSCC). However, the prognosis remains poor and more intensive neoadjuvant treatment might be needed to improve patient outcomes. We therefore aimed to compare the efficacy and safety of neoadjuvant doublet chemotherapy, triplet chemotherapy, and doublet chemotherapy plus radiotherapy in patients with previously untreated locally advanced OSCC. In this randomised, open-label, phase 3 trial, patients aged 20–75 years with previously untreated locally advanced OSCC and an Eastern Cooperative Oncology Group performance status of 0 or 1 were recruited from 44 centres across Japan. Patients were randomly assigned (1:1:1) centrally via a web-based system to receive neoadjuvant doublet chemotherapy (two courses of fluorouracil [800 mg/m2 per day intravenously on days 1–5] and cisplatin [80 mg/m2 per day on day 1] separated by an interval of 3 weeks [NeoCF]), triplet chemotherapy (three courses of fluorouracil [750 mg/m2 per day on days 1–5], cisplatin [70 mg/m2 per day on day 1], and docetaxel [70 mg/m2 per day on day 1] repeated every 3 weeks [NeoCF+D]), or doublet chemotherapy (two courses of fluorouracil [1000 mg/m2 per day on days 1–4] and cisplatin [75 mg/m2 per day on day 1] separated by an interval of 4 weeks) plus 41·4 Gy radiotherapy [NeoCF+RT]) followed by oesophagectomy with regional lymph node dissection. Randomisation was stratified by T stage and institution. Participants, investigators, and those assessing outcomes were not masked to group assignment. The primary endpoint was overall survival, analysed by intention to treat. Analysis of safety included all patients who received at least one course of chemotherapy, and analysis of surgical complications included those who also underwent surgery. This study is registered with the Japan Registry of Clinical Trials, jRCTs031180202, and the trial is complete. A total of 601 patients (529 male individuals and 72 female individuals) were randomly assigned between Dec 5, 2012, and July 20, 2018, with 199 patients in the NeoCF group, 202 patients in the NeoCF+D group, and 200 patients in the NeoCF+RT group. Compared with the NeoCF group, during a median follow-up period of 50·7 months (IQR 23·8–70·7), the 3-year overall survival rate was significantly higher in the NeoCF+D group (72·1% [95% CI 65·4–77·8] vs 62·6% [55·5–68·9]; hazard ratio [HR] 0·68, 95% CI 0·50–0·92; p=0·006) but not in the NeoCF+RT group (68·3% [61·3–74·3]; HR 0·84, 0·63–1·12; p=0·12). Grade 3 or higher febrile neutropenia occurred in two (1%) of 193 patients in the NeoCF group, 32 (16%) of 196 patients in the NeoCF+D group, and nine (5%) of 191 patients in the NeoCF+RT group. Treatment-related adverse events leading to termination of neoadjuvant therapy were more common in the NeoCF+D group (18 [9%] of 202 participants) than in the NeoCF+RT group (12 [6%] of 200) and NeoCF group (eight [4%] of 199). There were three (2%) treatment-related deaths during neoadjuvant therapy in the NeoCF group, four (2%) deaths in the NeoCF+D group, and two (1%) deaths in the NeoCF+RT group. Grade 2 or higher postoperative pneumonia, anastomotic leak, and recurrent laryngeal nerve paralysis were reported in 19 (10%), 19 (10%), and 28 (15%) of 185 patients, respectively, in the NeoCF group; 18 (10%), 16 (9%), and 19 (10%) of 183 patients, respectively, in the NeoCF+D group; and 23 (13%), 23 (13%), and 17 (10%) of 178 patients, respectively, in the NeoCF+RT group. The in-hospital deaths following surgery included three deaths in the NeoCF group, two deaths in the NeoCF+D group, and one in the NeoCF+RT group. Neoadjuvant triplet chemotherapy followed by oesophagectomy resulted in a statistically significant overall survival benefit compared with doublet chemotherapy and might be the new standard of care for locally advanced OSCC who are in good condition in Japan. Neoadjuvant doublet chemotherapy plus radiotherapy did not show significant improvement of survival compared with doublet chemotherapy. Japan Agency for Medical Research and Development and National Cancer Center Research and Development Fund.

Lutetium-177 [177Lu]Lu-prostate-specific membrane antigen (PSMA)-617 improves survival and quality of life in patients with metastatic castration-resistant prostate cancer, but whether it confers a benefit in hormone-sensitive disease is unknown. We aimed to evaluate [177Lu]Lu-PSMA-617 before docetaxel treatment in patients with de-novo high-volume metastatic hormone-sensitive prostate cancer. UpFrontPSMA was an investigator-initiated, multicentre, open-label, randomised, phase 2 trial done at 11 Australian hospitals. Eligible patients had prostate adenocarcinoma without clinically significant neuroendocrine differentiation or small-cell histology, were aged 18 years or older, had less than 4 weeks on androgen deprivation therapy, had an Eastern Cooperative Oncology Group performance status of 0–2, and had high-volume PSMA-avid disease on [68Ga]Ga-PSMA-11 PET-CT with no major discordance on 2-[18F] fluorodeoxyglucose-PET-CT. Patients were randomly assigned (1:1) to the experimental treatment ([177Lu]Lu-PSMA-617 followed 6 weeks later by docetaxel) or standard-of-care treatment (docetaxel alone) using computer-based block randomisation with random block sizes, stratified by disease volume by conventional imaging and duration of androgen deprivation therapy at the time of registration. Neither patients nor investigators were masked to treatment assignment. Patients in the experimental group received two cycles of [177Lu]Lu-PSMA-617 7·5 GBq every 6 weeks intravenously, followed 6 weeks later by six cycles of docetaxel 75 mg/m2 every 3 weeks intravenously, whereas patients in the standard-of-care treatment group received six cycles of docetaxel 75 mg/m2 every 3 weeks intravenously. All patients received continuous androgen deprivation therapy. The primary endpoint was undetectable prostate-specific antigen (≤0·2 ng/mL) at 48 weeks, assessed using a modified intention-to-treat analysis. The trial is registered with ClinicalTrials.gov, NCT04343885. Between May 5, 2020, and April 18, 2023, 130 patients were randomly assigned, 63 (48%) to [177Lu]Lu-PSMA-617 plus docetaxel and 67 (52%) to docetaxel alone. All patients were male and no race or ethnicity data were collected. Median follow-up was 2·5 years (IQR 1·8–3·0). Four patients in the docetaxel alone group withdrew consent after randomisation and no data beyond screening were collected. An additional four patients were not evaluable for the primary endpoint at 48 weeks (two in each group). 25 (41%) of 61 patients (95% CI 30–54) in the [177Lu]Lu-PSMA-617 plus docetaxel group had undetectable PSA at 48 weeks compared with ten (16%) of 61 patients (9–28) in the docetaxel alone group (OR 3·88, 95% CI 1·61–9·38; p=0·0020). The most common grade 3 or 4 treatment-related adverse events were febrile neutropenia (seven [11%] of 63 patients in the [177Lu]Lu-PSMA-617 plus docetaxel group vs six [10%] of 63 patients in the docetaxel alone group) and diarrhoea (four [6%] of 63 patients vs none). Serious adverse events occurred in 16 (25%) patients in the [177Lu]Lu-PSMA-617 plus docetaxel group (none were definitely related to [177Lu]Lu-PSMA-617) and 16 (25%) patients in the docetaxel alone group. No treatment-related deaths occurred. [177Lu]Lu-PSMA-617 followed by docetaxel improved antitumour activity in patients with de-novo high-volume metastatic hormone-sensitive prostate cancer compared with docetaxel alone, without increased toxic effects. Our data potentially support a role for [177Lu]Lu-PSMA-617 in metastatic hormone-sensitive prostate cancer. Prostate Cancer Research Alliance (Movember Foundation and Australian Government Medical Research Future Fund), US Department of Defence Impact Award-Clinical Trials, Endocyte/Advanced Accelerator Applications (a Novartis company), Australian Nuclear Science and Technology Organization, Victorian Cancer Agency, University of Melbourne, and Peter MacCallum Cancer Foundation.

AbstractObjectiveTo compare the efficacy and safety of sacituzumab tirumotecan (sac-TMT) with docetaxel in patients with locally advanced or metastatic epidermal growth factor receptor (EGFR)-mutated non-small cell lung cancer (NSCLC) after previous treatment failure with EGFR-tyrosine kinase inhibitors and platinum based chemotherapy.DesignMulticentre, open label, randomised controlled trial.Setting48 centres in China, 1 September 2023 to 31 December 2024.Participants137 adults (aged 18-75 years) with EGFR-mutated advanced or metastatic NSCLC after previous treatment failure with EGFR-tyrosine kinase inhibitors and platinum based chemotherapy.InterventionPatients were randomly assigned (2:1) to receive sac-TMT (5 mg/kg) on days 1 and 15 of each four week cycle, or docetaxel (75 mg/m2) on day 1 of each three week cycle. Patients in the docetaxel group were permitted to crossover to sac-TMT treatment on disease progression.Main outcome measuresThe primary endpoint was objective response rate as assessed by a blinded independent review committee (BIRC). The secondary endpoints included objective response rate assessed by the investigator; disease control rate, progression-free survival, time to response, and duration of response assessed by BIRC and the investigator; overall survival; and safety.Results137 patients were randomised to receive sac-TMT (n=91) or docetaxel (n=46). Median follow-up was 12.2 months at the data cut-off for efficacy (31 December 2024). BIRC assessed objective response rate was significantly higher in the sac-TMT group (45% (41/91)) v docetaxel (16% (7/45)), with a difference of 29% (95% confidence interval (CI) 15% to 43%; one sided P<0.001). Median progression-free survival was longer with sac-TMT than with docetaxel assessed by BIRC (6.9 v 2.8 months; hazard ratio 0.30, 95% CI 0.20 to 0.46; one sided P<0.001) and the investigator (7.9 v 2.8 months; hazard ratio 0.23, 0.15 to 0.36; one sided P<0.001). The 12 month overall survival rate was 73% with sac-TMT and 54% with docetaxel (hazard ratio 0.49, 0.27 to 0.88; one sided P=0.007). After adjustment for crossover using the rank-preserving structural failure time model, sac-TMT also showed improved overall survival (hazard ratio 0.36, 0.20 to 0.66). Grade ≥3 treatment related adverse events were less frequent with sac-TMT than with docetaxel (56% v 72%), with no new safety signals identified.ConclusionsSac-TMT showed statistically significant and clinically meaningful improvements in objective response rate, progression-free survival, and overall survival compared with docetaxel, with a manageable safety profile in patients with EGFR-mutated locally advanced or metastatic NSCLC.Trial registrationClinicalTrials.gov NCT05631262.

Results from a phase 2 trial of the TPEx chemotherapy regimen (docetaxel–platinum–cetuximab) showed promising results, with a median overall survival of 14·0 months in first-line recurrent or metastatic head and neck squamous-cell carcinoma (HNSCC). We therefore aimed to compare the efficacy and safety of the TPEx regimen with the standard of care EXTREME regimen (platinum–fluorouracil–cetuximab) in this setting. This was a multicentre, open-label, randomised, phase 2 trial, done in 68 centres (cancer centres, university and general hospitals, and private clinics) in France, Spain, and Germany. Eligible patients were aged 18–70 years with histologically confirmed recurrent or metastatic HNSCC unsuitable for curative treatment; had at least one measurable lesion according to Response Evaluation Criteria in Solid Tumors version 1.1; and had an Eastern Cooperative Oncology Group (ECOG) performance status of 1 or less. Participants were randomly assigned (1:1) using the TenAlea website by investigators or delegated clinical research associates to the TPEx regimen or the EXTREME regimen, with minimisation by ECOG performance status, type of disease evolution, previous cetuximab treatment, and country. The TPEx regimen consisted of docetaxel 75 mg/m2 and cisplatin 75 mg/m2, both intravenously on day 1, and cetuximab on days 1, 8, and 15 (intravenously 400 mg/m2 on day 1 of cycle 1 and 250 mg/m2 weekly subsequently). Four cycles were repeated every 21 days with systematic granulocyte colony-stimulating factor (G-CSF) support at each cycle. In case of disease control after four cycles, intravenous cetuximab 500 mg/m2 was continued every 2 weeks as maintenance therapy until progression or unacceptable toxicity. The EXTREME regimen consisted of fluorouracil 4000 mg/m2 on day 1–4, cisplatin 100 mg/m2 on day 1, and cetuximab on days 1, 8, and 15 (400 mg/m2 on day 1 of cycle 1 and 250 mg/m2 weekly subsequently) all delivered intravenously. Six cycles were delivered every 21 days followed by weekly 250 mg/m2 cetuximab as maintenance therapy in case of disease control. G-CSF support was not mandatory per the protocol in the EXTREME regimen. The primary endpoint was overall survival in the intention-to-treat population; safety was analysed in all patients who received at least one dose of chemotherapy or cetuximab. Enrolment is closed and this is the final analysis. This study is registered at ClinicalTrials.gov, NCT02268695. Between Oct 10, 2014, and Nov 29, 2017, 541 patients were enrolled and randomly assigned to the two treatment regimens (271 to TPEx, 270 to EXTREME). Two patients in the TPEx group had major deviations in consent forms and were not included in the final analysis. Median follow-up was 34·4 months (IQR 26·6–44·8) in the TPEx group and 30·2 months (25·5–45·3) in the EXTREME group. At data cutoff, 209 patients had died in the TPEx group and 218 had died in the EXTREME group. Overall survival did not differ significantly between the groups (median 14·5 months [95% CI 12·5–15·7] in the TPEx group and 13·4 months [12·2–15·4] in the EXTREME group; hazard ratio 0·89 [95% CI 0·74–1·08]; p=0·23). 214 (81%) of 263 patients in the TPEx group versus 246 (93%) of 265 patients in the EXTREME group had grade 3 or worse adverse events during chemotherapy (p<0·0001). In the TPEx group, 118 (45%) of 263 patients had at least one serious adverse event versus 143 (54%) of 265 patients in the EXTREME group. 16 patients in the TPEx group and 21 in the EXTREME group died in association with adverse events, including seven patients in each group who had fatal infections (including febrile neutropenia). Eight deaths in the TPEx group and 11 deaths in the EXTREME group were assessed as treatment related, most frequently sepsis or septic shock (four in each treatment group). Although the trial did not meet its primary endpoint, with no significant improvement in overall survival with TPEx versus EXTREME, the TPEx regimen had a favourable safety profile. The TPEx regimen could provide an alternative to standard of care with the EXTREME regimen in the first-line treatment of patients with recurrent or metastatic HNSCC, especially for those who might not be good candidates for up-front pembrolizumab treatment. Merck Santé and Chugai Pharma.

AbstractObjectiveTo evaluate the feasibility of using a multigene signature to tailor individualised adjuvant therapy for patients with operable triple negative breast cancer.DesignRandomised, multicentre, open label, phase 3 trial.Setting7 cancer centres in China between 3 January 2016 and 17 July 2023.ParticipantsFemale patients aged 18-70 years with early triple negative breast cancer after definitive surgery.InterventionsAfter risk stratification using the integrated signature, patients at high risk were randomised (1:1) to receive an intensive adjuvant treatment comprising four cycles of docetaxel, epirubicin, and cyclophosphamide followed by four cycles of gemcitabine and cisplatin (arm A; n=166) or a standard treatment of four cycles of epirubicin and cyclophosphamide followed by four cycles of docetaxel (arm B; n=170). Patients at low risk received the same adjuvant chemotherapy as arm B (arm C; n=168).Main outcome measuresThe primary endpoint was disease-free survival in the intention-to-treat analysis for arm A versus arm B. Secondary endpoints included disease-free survival for arm C versus arm B, recurrence-free survival, overall survival, and safety.ResultsAmong the 504 enrolled patients, 498 received study treatment. At a median follow-up of 45.1 months, the three year disease-free survival rate was 90.9% for patients in arm A and 80.6% for patients in arm B (hazard ratio 0.51, 95% confidence interval (CI) 0.28 to 0.95; P=0.03). The three year recurrence-free survival rate was 92.6% in arm A and 83.2% in arm B (hazard ratio 0.50, 95% CI 0.25 to 0.98; P=0.04). The three year overall survival rate was 98.2% in arm A and 91.3% in arm B (hazard ratio 0.58, 95% CI 0.22 to 1.54; P=0.27). The rates of disease-free survival (three year disease-free survival 90.1% v 80.6%; hazard ratio 0.57, 95% CI 0.33 to 0.98; P=0.04), recurrence-free survival (three year recurrence-free survival 94.5% v 83.2%; 0.42, 0.22 to 0.81; P=0.007), and overall survival (three year overall survival 100% v 91.3%; 0.14, 0.03 to 0.61; P=0.002) were significantly higher in patients in arm C than in those in arm B with the same chemotherapy regimen. The incidence of grade 3-4 treatment related adverse events were 64% (105/163), 51% (86/169), and 54% (90/166) for arms A, B, and C, respectively. No treatment related deaths occurred.ConclusionsThe multigene signature showed potential for tailoring adjuvant chemotherapy for patients with operable triple negative breast cancer. Intensive regimens incorporating gemcitabine and cisplatin into anthracycline/taxane based therapy significantly improved disease-free survival with manageable toxicity.Trial registrationClinicalTrials.gov NCT02641847.

Purpose The systemic immune-inflammation index (SII) is a hematological marker that reflects the immune status of the body. This study was designed to evaluate the prognostic significance of the baseline SII in HER2-positive metastatic breast cancer (MBC) patients receiving chemotherapy plus trastuzumab without or with pertuzumab. Methods Data were collected from 774 patients from the CLEOPATRA trial, 196 patients from the H0648G trial, and 229 patients from six clinical centers in China. Patients were divided into the low and high SII subgroups according to the median SII value. The inverse probability of treatment weighting (IPTW) method was used to control bias. Associations between the SII and progression-free survival (PFS) and overall survival (OS) were analyzed. Results In the CLEOPATRA trial, a lower SII was associated with better PFS (hazard ratio [HR] 1.31, 95% confidence interval [CI] 1.04–1.65, P = 0.02) and OS (HR 1.42, 95% CI 1.07–1.88, P = 0.02) in the trastuzumab and docetaxel groups, as well as improved PFS in the trastuzumab and pertuzumab and docetaxel groups (HR 1.39, 95% CI 1.10–1.77, P < 0.01) after IPTW. In the H0648G trial, a lower SII was associated with better PFS ( P = 0.04) and OS ( P = 0.02) in HER2-positive MBC patients receiving trastuzumab-based therapy. According to real-world data, a lower SII predicted an improvement in PFS for patients treated with docetaxel plus trastuzumab without or with pertuzumab ( P = 0.02 and 0.01, respectively). Conclusions A low baseline SII is associated with better survival outcomes among HER2-positive MBC patients receiving trastuzumab-based first-line therapy.