Frankel, Wendy L.

1 Background: To determine whether changing chemotherapy (CT) during pre-op chemoradiation (CRT) based on response to induction CT by 18F-fluoro-deoxyglucose PET imaging can lead to improved pathologic complete response (pCR) in patients (pts) with resectable esophageal and gastroesophageal junction (GEJ) adenocarcinomas. Methods: 257 eligible pts were enrolled, underwent baseline PET scan, and were randomized to one of 2 induction CT arms: Modified FOLFOX-6 (oxaliplatin, leucovorin, 5-FU), days 1, 15, 29 or Carboplatin/Paclitaxel (CP), days 1, 8, 22, 29. Repeat PET was performed days 36-42; change in max standardized uptake value (SUV) from baseline was assessed. PET non-responders (≤35% decrease in SUV – PET-NR) crossed over to alternative CT regimen during CRT (50.4Gy/28 fractions). PET responders (>35% decrease in SUV – PET-R) continued on same CT during CRT. Pts underwent surgery 6 wks post-CRT. Pts evaluable if had surgery, disease progression (PD), death due to disease, were unresectable or had adverse event (AE). Primary endpoint was pCR in PET-NR who crossed over to alternative CT (expected 5% under H0 to 20% under Ha). Results: Pre-audit PET response data after induction CT and pCR rates after CRT and surgery are shown in the table. For PET-NR who crossed over to alternative CT during CRT, pCR was 15.6%; 95% CI (0.08, 0.26). Conclusions: Efficacy criteria were met for an improvement in pCR rates among pts who were PET-NR after induction CT and received alternative CT during CRT for esophageal and GEJ adenoca. Pts receiving induction and concurrent CP had an unexpectedly low pCR. Support: U10CA180821, U10CA180882 Clinical trial information: NCT01333033. [Table: see text]

Abstract The MutLα heterodimer formed by mismatch repair (MMR) proteins MLH1 and PMS2 is a major component of the MMR complex, yet mutations in the PMS2 gene are rare in the etiology of hereditary nonpolyposis colorectal cancer. Evidence from five published cases suggested that contrary to the Knudson principle, PMS2 mutations cause hereditary nonpolyposis colorectal cancer or Turcot syndrome only when they are biallelic in the germline or abnormally expressed. As candidates for PMS2 mutations, we selected seven patients whose colon tumors stained negative for PMS2 and positive for MLH1 by immunohistochemistry. After conversion to haploidy, truncating germline mutations of PMS2 were found in two patients (2192delTAACT and deletion of exon 8). These mutations abrogated PMS2 protein in germline cells by Western analysis. In two additional patients, PMS2 protein from one allele also was abrogated. Novel or previously described missense variants of PMS2 were detected, but their pathogenicity is undetermined. We detected and characterized a new transcript, PMS2CL, showing 98% sequence identity with exons 9 and 11–15 of PMS2 and emanating from a locus close to PMS2 in chromosome 7p. Its predicted protein product was not detected. Thus, in addition to several previously described PMS2-related genes resembling the 5′ end of PMS2, at least one related gene resembles the 3′ end of PMS2. In conclusion, both detectable and presently undefined germline mutations are deleterious and produce susceptibility to cancer by the two-hit mechanism. Paralogous genes interfere with mutation detection, resulting in underdiagnosis of PMS2 mutations. Mutation detection in PMS2 requires haploid DNA.