Circulating tumor DNA (ctDNA) during and after neoadjuvant chemotherapy and prior to surgery is a powerful prognostic factor in triple-negative breast cancer (TNBC).

Abstract

594 Background: TNBC, the most aggressive form of breast cancer, is treated primarily with chemotherapy, even before surgery (neoadjuvant chemotherapy or NAC). The prognosis and need for adjuvant therapy depends greatly on the tumor response assessed by pathology (pCR). Highly sensitive and specific ctDNA assays have been shown to be of prognostic value in the metastatic settingbut not yet in earlier settings. Methods: Tissue was collected from 26 Q-CROC-03 clinical trial TNBC patients before, during and after NAC, prior to surgery. Whole exome sequencing on tumor tissues was used to select single nucleotide variants with high allele frequency (VAF), prioritizing TP53, to generateindividual digital droplet PCR (ddPCR) assays. An average of 5 variants (range 1-12) per patient were tested, for a total of 121 variants. A detection threshold was defined for each variant from a pool of normal controls. Median follow-up was 55 months. Results: ctDNA was detectable in 96% of patients at baseline, but 20% of the 121 variants were not detectable at any time point. At baseline, the mean VAF of all analyzed variants, but not of TP53 variants alone, was significantly correlated (p < 0.05) with tumor factors (tumor size, stage, grade, nodal status before and at surgery, RCB score) but not with patient age or BRCA1/2 mutation status. 87 variants (74%) were detected at baseline and their VAF fell by 86% after 1 cycle of chemotherapy (T1). The detection of ctDNA at T1 was associated with DFS (p = 0.027) while the detection of ctDNA at the last post-chemotherapy pre-surgery time point (T4) was strongly associated with pathological complete response (pCR) and both DFS (p = 0.013) and OS(p = 0.006). At this time point, 5 of 41 variants (12%) were detected in pCR patients vs 42 of 80 (53%) in non-pCR, while only 6 of the 15 (40%) non-pCR patients had detectable TP53 variants. Interestingly, for variants detected at baseline, the positive predictive value of T4 ctDNA for disease recurrence was 69%, similar to that of non-pCR, while the negative predictive value of no ctDNA at T4 was 89% for disease recurrence vs 80% for pCR. Conclusions: ctDNA detection after NAC prior to surgery is strongly predictive of disease-free survival and overall survival and is comparable to pCR as a prognostic factor in our cohort (NCT01276899).

Identifying Biomarkers to Pair with Targeting Treatments within Triple Negative Breast Cancer for Improved Patient Stratification

“…Presence of ctDNA within both the single time point and serial sampling could predict relapse across tumour types including within TNBC patients (p = 0.009 and 0.003) [65]. Sample size was small with just 11 and 13 TNBC patients with available samples for single time-point and serial sampling respectively, the results however are supported by other small studies restricted to TNBC patients with similar findings [66,67] suggesting the potential for ctDNA as a biomarker for relapse. What is currently less clear is whether ctDNA detection can be used to direct treatment.…”

Signed in Blood: Circulating Tumor DNA in Cancer Diagnosis, Treatment and Screening

“…To date, multiple studies have analyzed the utility of ctDNA to be able to assess disease-free survival (DFS) and overall survival (OS) (Table 3) [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67]. Factors that predict poorer outcomes include concordance between tissue and liquid ctDNA alterations (shown for both TP53 and KRAS mutations) [68,69], higher percent ctDNA (perhaps reflecting higher tumor burden, and higher number of ctDNA alterations [14].…”

“…Multiple studies have shown that ctDNA can be an important prognostic factor. For instance, in triple-negative breast cancer patients who had received or were receiving neoadjuvant chemotherapy, the detection of ctDNA was associated with a significantly worse DFS (p = 0.027) [53]. Additionally, at the last post-chemotherapy pre-surgery time point, detection of ctDNA was strongly associated with shorter DFS (p = 0.013) and OS (p = 0.006) [53].…”

“…For instance, in triple-negative breast cancer patients who had received or were receiving neoadjuvant chemotherapy, the detection of ctDNA was associated with a significantly worse DFS (p = 0.027) [53]. Additionally, at the last post-chemotherapy pre-surgery time point, detection of ctDNA was strongly associated with shorter DFS (p = 0.013) and OS (p = 0.006) [53]. In patients receiving adjuvant chemotherapy for locally advanced rectal cancer, 122 (77%) of 159 patients had pre-surgical detectable ctDNA and after surgery only 12 of 140 (8.6%) with negative ctDNA (hazard ratio (HR) 12, p < 0.001) experienced recurrence [54].…”

Biomarkers in Triple-Negative Breast Cancer: State-of-the-Art and Future Perspectives

“…Despite this, pCR rate was not correlated with ctDNA detection at any time point, while ctDNA positivity after one cycle of chemotherapy was correlated with shorter DFS and OS [ 262 ]. Furthermore, Cavallone et al reported that ctDNA detection after neoadjuvant chemotherapy and before surgery was associated to DFS and OS [ 263 ]. A phase II clinical trial (NCT03145961) is recruiting patients to evaluate whether ctDNA detection can be used to detect residual disease after standard primary treatment in early-stage TNBC.…”