Abstract 1379
Background
MMR testing is performed to screen Lynch Syndrome, evaluate the prognosis of colorectal cancer (CRC) and predict the efficacy of PD1/PDL1 blockade in all tumor types. Two methods are available: immunohistochemistry (IHC) using antibodies against MMR proteins and molecular biology (MB) for assessing microsatellite instability (MSI). Classically, dMMR tumor corresponds to loss of expression of two proteins (MLH1 and PMS2 or MSH2 and MSH6) associated with MSI. Atypical profiles of dMMR tumors have sporadically been described. The aim of our study was to describe the frequency and characteristics of these atypical cases.
Methods
All MMR testing performed in our center between 2007 and 2017 were checked to select cases with both available IHC and MB. Then, all dMMR cases were reviewed to identify atypical cases which were defined by: isolated loss of expression of one protein, loss of expression of two proteins without MSI, normal expression of the four proteins with MSI, aberrant loss of proteins, or MSI-low. Biological data of atypical cases were controlled and clinical data were collected for each case.
Results
4948 MMR tests were performed, 3800 had both available IHC and MB data, and 585 were dMMR (15 %). Among them, 97 cases were atypical and after biological control, 8 cases were re-classified typical; allowing to finally identify 89 atypical cases: 60 CRC, 10 endometrial carcinoma, 8 digestive non CRC and 11 others types of cancers. A strong correlation with genetic syndromes was observed for those atypical profiles.Table:
2015P
Isolated PMS2 or MSH6 loss n = 53 | Expression of the four proteins n = 5 | MSH2/MSH6 or MLH1/PMS2 loss n = 16 | Aberrant loss of proteins n = 15 | |
---|---|---|---|---|
MSI | 43 | 3 | - | 13 |
MSI low | 1 | 2 | 8 | - |
MSS * | 9 | - | 8 | 2 |
Clinical characteristics | Predominantly CCR Genetic predisposition syndrome (73%) | Exclusively CCR or endometrial Genetic predisposition syndrome (≥40%) | Predominantly Non CRC (63%) | None |
(* MSS: microsatellite stability)
Conclusions
Even using controlled IHC and MB, 15% of dMMR tumors have an atypical profile. These atypical cases mainly involve non CRC cancer with a strong prediction for Lynch syndrome. Their therapeutic impact particularly for immunotherapy should be now evaluated.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.
Resources from the same session
5519 - Is there a difference of Palliative care problems and needs between cancer and non-cancer hospitalized elderly patients?
Presenter: Ioanna Chatzi
Session: Poster Display session 1
Resources:
Abstract
2505 - There is a lack of clinical research for patients with cancer in palliative care
Presenter: Marie Vinches
Session: Poster Display session 1
Resources:
Abstract
5273 - Specialist Palliative Care (SPC) in Haematological Malignancy: Establishing practices in a UK Tertiary Cancer Centre (TCC)
Presenter: Emma Kedgley
Session: Poster Display session 1
Resources:
Abstract
5864 - Evaluation of the relationship between the attachment styles and psychological resilience of cancer patients receiving chemotherapy
Presenter: Fatma Bugdayci Basal
Session: Poster Display session 1
Resources:
Abstract
770 - Gefitinib along with Methotrexate as palliative therapy in PS 3 and above in metastatic squamous cell carcinoma head and neck cancer patients
Presenter: Vidya Dusi
Session: Poster Display session 1
Resources:
Abstract
4232 - High intensity end-of-life care in pediatrics, adolescent and young adult patients with cancer using an administrative database.
Presenter: Seiko Bun
Session: Poster Display session 1
Resources:
Abstract
4845 - Embedded outpatient palliative care service within the oncology clinic: Preliminary experience in Hacettepe Oncology Hospital
Presenter: Deniz Can Guven
Session: Poster Display session 1
Resources:
Abstract
3270 - Internet-based stepped care for individuals with cancer and concurrent anxiety or depression symptoms – results from a randomized controlled trial
Presenter: Birgitta Johansson
Session: Poster Display session 1
Resources:
Abstract
5503 - Impact of Cognitive-Behavioral-Therapy (CBT) on levels of anxiety, depression and distress in cancer patients (pts)
Presenter: Daniela Tregnago
Session: Poster Display session 1
Resources:
Abstract
5553 - Cytokine genetic variations and worse quality of life among family caregivers of head and neck cancer patients in palliative care
Presenter: Daniel Pequeno
Session: Poster Display session 1
Resources:
Abstract