BackgroundAccurate measurement of tumor burden in breast cancer disease is essential to improve the clinical management of patients. In this study, we evaluate whether the fluctuations in the fraction of PIK3CA mutant allele correlates with tumor response according to RECIST criteria and tumor markers quantification.MethodsEighty six plasma samples were analyzed by digital PCR using Rare Mutation Assays for E542K, E545K and H1047R. Mutant cfDNA and tumor markers CA15-3 and CEA were compared with radiographic imaging.ResultsThe agreement between PIK3CA mutation status in FFPE samples and circulating tumor DNA (ctDNA) was moderate (K = 0.591; 95% IC = 0.371–0.811). Restricting the analysis to the metastatic patients, we found a good agreement between PIK3CA mutation status assessed in liquid and solid biopsy (K = 0.798 95%; IC = 0.586–1). ctDNA showed serial changes with fluctuations correlating with tumor markers 15.3 and CEA in 7 out of 8 cases with Pearson correlation coefficients ranging from 0.99 to 0.46 and from 0.99 to 0.38 respectively. Similarly, fluctuations in the fraction of PIK3CA mutant allele always correlated with changes in lesion size seen on images, although in two cases it did not correlate with treatment responses as defined by RECIST criteria.Conclusiononcogenic mutation quantification in plasma samples can be useful to monitor treatment outcome. However, it might be limited by tumor heterogeneity in advanced disease and it should be evaluated together with radiographic imaging.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-017-3185-9) contains supplementary material, which is available to authorized users.

The distribution of the hemoglobin Constant Spring (Hb CS) gene in eight populations in Southeast Asia (including Assam) was determined using oligonucleotide hybridization. Hb CS was absent in two Assamese populations with a high prevalence of Hb E. The Hb CS gene frequency was 0.033 in northern Thailand and near 0.01 in central Thailand and Cambodia. High frequencies, between 0.05 and 0.06, were observed in northeastern Thailand. The present data and a similar study in Laotians suggest that the Lao-speaking populations of the Mekong River basin in northeastern Thailand and Laos have the highest frequencies of the Hb CS gene in Southeast Asia.

DNA haplotypes (HT) and frameworks (FW) linked to the beta-globin locus were determined by restriction fragment analysis using eight restriction enzymes on chromosomes bearing the Hb A gene (HBB*A) or the HbE gene (HBB*E) in the So, an Austro-Asiatic population of northeast Thailand with an HBB*E frequency near 0.5. All HBB*E genes were present with FW2, and only two haplotypes were observed (25 HT 27-2, -+- +-; 10 HT 41-2, +----++-). In a control group from the general population of Northeast Thailand the HT distribution was more diverse, and 2 of 20 HBB*E genes were present in FW 3. High frequencies of HBB*E in FW 3 in Southeast Asia are apparently limited to the Khmer population of Cambodia. There were no differences in the hematologic parameters in subjects homozygous for HBB*E/FW2 or HBB*E/FW3.