Establishment of patient-derived tumor organoids to functionally inform treatment decisions in metastatic colorectal cancer

BACKGROUND

Metastatic colorectal cancer (mCRC) patients tend to have modest benefits from molecularly driven therapeutics. Patient-derived tumor organoids (PDTOs) represent an unmatched model to elucidate tumor resistance to therapy, due to their high capacity to resemble tumor characteristics.

MATERIALS AND METHODS

We used viable tumor tissue from two cohorts of patients with mCRC, naïve or refractory to treatment, respectively, for generating PDTOs. The derived models were subjected to a 6-day drug screening assay (DSA) with a comprehensive pipeline of chemotherapy and targeted drugs against almost all the actionable mCRC molecular drivers. For the second cohort DSA data were matched with those from PDTO genotyping.

RESULTS

A total of 40 PDTOs included in the two cohorts were derived from mCRC primary tumors or metastases. The first cohort included 31 PDTOs derived from patients treated in front line. For this cohort, DSA results were matched with patient responses. Moreover, RAS/BRAF mutational status was matched with DSA cetuximab response. Ten out of 12 (83.3%) RAS wild-type PDTOs responded to cetuximab, while all the mutant PDTOs, 8 out of 8 (100%), were resistant. For the second cohort (chemorefractory patients), we used part of tumor tissue for genotyping. Four out of nine DSA/genotyping data resulted applicable in the clinic. Two RAS-mutant mCRC patients have been treated with FOLFOX-bevacizumab and mitomycin-capecitabine in third line, respectively, based on DSA results, obtaining disease control. One patient was treated with nivolumab-second mitochondrial-derived activator of caspases mimetic (phase I trial) due to high tumor mutational burden at genotyping, experiencing stable disease. In one case, the presence of BRCA2 mutation correlated with DSA sensitivity to olaparib; however, the patient could not receive the therapy.

CONCLUSIONS

Using CRC as a model, we have designed and validated a clinically applicable methodology to potentially inform clinical decisions with functional data. Undoubtedly, further larger analyses are needed to improve methodology success rates and propose suitable treatment strategies for mCRC patients.

Cetuximab as third-line rechallenge plus either irinotecan or avelumab is an effective treatment in metastatic colorectal cancer patients with baseline plasma RAS/BRAF wild-type circulating tumor DNA: Individual patient data pooled analysis of CRICKET and CAVE trials

The rechallenge strategy is based on the concept that a subset of patients with RAS wild-type (WT) metastatic colorectal cancer (mCRC) could still benefit of epidermal growth factor receptor (EGFR) inhibition, after progression to an anti-EGFR based-therapy. We performed a pooled analysis of two-phase II prospective trials to determine the role of rechallenge in third-line mCRC patients with RAS/BRAF WT baseline circulating tumor DNA (ctDNA). Individual data of 33 and 13 patients from CAVE and CRICKET trials that received as third-line therapy cetuximab rechallenge were collected. Overall survival (OS), Progression-free survival (PFS), Overall response rate (ORR), Stable disease (SD) >6 months were calculated. Adverse events were reported. For the whole 46 patient population, median PFS (mPFS) was 3.9 months (95% Confidence Interval, CI 3.0-4.9) with median OS (mOS) of 16.9 months (95% CI 11.7-22.1). For CRICKET patients, mPFS was 3.9 months (95% CI 1.7-6.2); mOS was 13.1 months (95% CI 7.3-18.9) with OS rates at 12, 18, and 24 months of 62%, 23%, and 0%, respectively. For CAVE patients, mPFS was 4.1 months (95% CI 3.0-5.2); mOS was 18.6 months (95% CI 11.7-25.4) with OS rates at 12, 18, 24 months of 61%, 52%, 21%, respectively. Skin rash was more frequently reported in CAVE trial (87.9% vs. 30.8%; p = 0.001), whereas a increased incidence of hematological toxicities was observed in CRICKET trial (53.8%% vs. 12.1%; p = 0.003). Third-line cetuximab rechallenge in combination with either irinotecan or avelumab in RAS/BRAF WT ctDNA mCRC patients represents a promising therapy.

Clinical efficacy of sequential treatments in KRASG12C-mutant metastatic colorectal cancer: findings from a real-life multicenter Italian study (CRC-KR GOIM)

Background

The presence of KRASG12C mutation in metastatic colorectal cancer (mCRC) correlates with poor outcome. Although different selective inhibitors are under clinical development, the optimal treatment remains uncertain. Thus, we conducted a retrospective analysis in a large cohort of patients with KRASG12C mCRC treated in 12 Italian oncology units.

Patients and methods

Patients with unresectable mCRC harboring KRASG12C mutation receiving a first-line chemotherapy doublet or triplet between 2011 and 2021 were included in the study. Evaluation of overall response rate (ORR), progression-free survival (PFS) and overall survival (OS) analysis was carried out.

Results

A total of 256/6952 (3.7%) patients with mCRC displayed KRASG12C mutation; of these, 111 met the inclusion criteria. The ORR of first-line therapy was 38.7% (43/111). Median PFS (mPFS) was 9 months [95% confidence interval (CI) 7.5-10.5 months]. After progression, only 62% and 36% of the patients are fit to receive second or third lines of treatment, with limited clinical benefit. Median OS (mOS) was 21 months (95% CI 17.4-24.6 months). In patients receiving first-line triplet chemotherapy, ORR was 56.3% (9/16), mPFS was 13 months (95% CI 10.3-15.7 months) and mOS was 32 months (95% CI 7.7-56.3 months). For irinotecan-based doublets, ORR was 34.5 (10/29), mPFS was 9 months (95% CI 6.4-11.6 months) and mOS was 22 months (95% CI 16.0-28.0 months). With oxaliplatin-based doublets ORR was 36.4% (24/62), mPFS was 7 months (95% CI 4.6-9.4 months) and mOS was 18 months (95% CI, 13.6-22.4 months).

Conclusion

Patients with KRASG12C-mutant mCRC had a disappointing response to standard treatments. Within the limitations of a retrospective study, these results suggest that first-line chemotherapy intensification with FOLFOXIRI is a valid option in fit patients.

•

KRASG12C mutation is rare and occurs in 3.7% of the study population.

•

The presence of KRASG12C mutation is correlated with an aggressive disease, with reduced response to chemotherapy.

•

Only 62% and 36% of patients with KRASG12C-mutant mCRC are fit to receive second or third lines of treatment, respectively.

•

The use of chemotherapy triplets is associated with improved outcomes compared with chemotherapy doublets.

Thyroid disorders following hematopoietic stem cell transplantation in childhood: the impact of the conditioning regimen on thyroid dysfunction, volume changes and occurrence of nodules

BACKGROUND

Thyroid late effects are among the most frequent sequelae reported after pediatric hematopoietic stem cell transplantation (HSCT). Though the detrimental effects of radiotherapy on the developing thyroid gland have been extensively assessed, the role of chemotherapy-only conditioning regimens is still controversial.

OBJECTIVE

We aimed at describing the occurrence, monitoring and management of thyroid function disorders (i.e. Graves' disease, Hashimoto thyroiditis and non-autoimmune hypothyroidism), nodules and volumetric changes over a 20-year observation period in a single pediatric transplant unit. In addition, we assessed the impact of different conditioning regimens on thyroid health.

STUDY

design Retrospective observational analysis. The study population included 244 patients transplanted for pediatric malignant or non-malignant diseases between 1999 and 2018 and for whom at least four thyroid function tests and one or more thyroid ultrasound(s) assessed sequentially after HSCT were available.

RESULTS

The 15-year cumulative incidence (CI) of either autoimmune or non-autoimmune thyroid dysfunctions (34%, SE 5.3%) did not statistically differ between total body irradiation- (TBI-) and chemo-based regimens (p 0.23). Indeed, the CI after busulfan (BU) was overall superimposable to that recorded after TBI (10-year CI: 22.2% versus 25.9%, respectively). Nevertheless, the CI of non-autoimmune hypothyroidism was statistically higher after BU- (12.4%, SE 3.7%) than after other chemotherapy only-based-conditionings (3.1%, SE 3.1%; p 0.02, 5-year CI), treosulfan included. The overall CI of nodules was low for the first 5 years after HSCT (1.9%, SE 0.9%), but it showed a subsequent steep increase over time, with a 15-year CI as high as 52.1% (SE 7.5%). TBI-conditioned patients experienced a higher 15-year CI of nodules (66.8%, SE 9.1%) compared to those receiving chemo-only regimens (33.6%, SE 9.5%; p 0.02), whereas age > 10 years upon transplantation showed a protective effect (HR 0.42, 95% confidence interval 0.2-0.88). Finally, a systematic sonographic follow-up highlighted a progressive statistically significant reduction in thyroid antero-posterior diameter among patients conditioned with TBI (p 0.005), but not after chemo-only regimens.

CONCLUSIONS

TBI and younger age upon HSCT play a remarkable and statistically demonstrated detrimental role on the occurrence of thyroid nodules, both benign and malignant. TBI and BU expose patients to a higher cumulative incidence of thyroid dysfunctions than other chemo-only regimens, treosulfan included. Accordingly, BU can be regarded as the most thyrotoxic agent among those administered as a part of a chemo-only conditioning regimen. Finally, patients conditioned with TBI, but not with other regimens, show a progressive decrease in thyroid volume over time, as assessed by sequential ultrasounds.

How we treat locoregional melanoma

Cutaneous melanoma is the most lethal form of skin cancer and its incidence has been increasing in the past 30 years. Although this is completely resectable in most cases, thicker melanoma and those with regional lymph-node involvement are at a high risk of relapse. In recent years, the management of locoregional disease has drastically changed. In particular, in the 8th Edition of the American Joint Committee on Cancer (AJCC), subgroup classification of TNM (tumor–node–metastasis) has been modified, with the addition of the IIID stage. Furthermore, in recent randomized trials, completion lymph node dissection in case of sentinel lymph node biopsy positivity has not been shown to offer any improvement in overall survival versus observation. Consequently, radical dissection has been recommended as the standard treatment, but only in patients with palpable nodal metastases. However, the major novelty in the treatment of locally advanced melanoma has been the introduction of drugs, already used for metastatic disease, that have also shown clinical efficacy in the adjuvant setting. In fact, immunotherapies and, in the case of BRAF V600E/K-mutated melanoma, combination treatment of BRAF and MEK inhibitors have improved recurrence-free survival in these patients. In this paper, we will describe the current management of a patient with radically resectable melanoma and discuss the key points in light of the latest scientific evidence.

•

Melanoma is the deadliest of skin cancers, although most cases are resectable at diagnosis.

•

Use of targeted therapies and immunotherapies as adjuvant treatment revolutionized the scenario in stage III melanoma.

•

In this review, we summarize all current evidence about locoregional melanoma, including open issues and future directions.

Role of Preoperative Adrenergic Blockade with Doxazosin on Hemodynamic Control during the Surgical Treatment of Pheochromocytoma: A Retrospective Study of 48 Cases

Authors evaluated the effects of selective adrenergic blockade by means of doxazosin on blood pressure in 48 patients operated on for pheochromocytoma by a multicenter retrospective study. Age, tumor size, surgical approach, and operative time were analyzed as predictive factors of intraoperative hypertensive crises. Forty-eight patients underwent adrenalectomy—four open surgery and 44 laparoscopic surgery—for pheochromocytoma of adrenal glands from 1998 to 2008 after preoperative administration of doxazosin. Perioperative cardiovascular status modifications and surgical medium- and long-term outcomes were analyzed. There was no mortality, conversion rate was 4.5 per cent, and morbidity rate was 8.3 per cent. Intraoperative hypertensive crises (180/ 90 mmHg or higher) were observed in 14.5 per cent (seven of 48) of patients and were treated pharmacologically with no aftermath. None of the examined variables influenced the occurrence of intraoperative hypertensive episodes. Postoperative hypotension (lower than 90/60 mmHg) was observed in four of 48 patients (8.3%) and was treated by crystalloids and hydrocortisone. In the surgical treatment of pheochromocytoma, the preoperative adrenergic blockade by doxazosin does not prevent intraoperative hypertensive crises. Nevertheless, in our series, they were of short duration and were not associated with major cardiovascular complications. Perioperative hemodynamic instability was managed bypreoperative pharmacological treatment, allowing low morbidity.

Triple blockade of EGFR, MEK and PD-L1 has antitumor activity in colorectal cancer models with constitutive activation of MAPK signaling and PD-L1 overexpression

BACKGROUND

Molecular mechanisms driving acquired resistance to anti-EGFR therapies in metastatic colorectal cancer (mCRC) are complex but generally involve the activation of the downstream RAS-RAF-MEK-MAPK pathway. Nevertheless, even if inhibition of EGFR and MEK could be a strategy for overcoming anti-EGFR resistance, its use is limited by the development of MEK inhibitor (MEKi) resistance.

METHODS

We have generated in vitro and in vivo different CRC models in order to underline the mechanisms of MEKi resistance.

RESULTS

The three different in vitro MEKi resistant models, two generated by human CRC cells quadruple wild type for KRAS, NRAS, BRAF, PI3KCA genes (SW48-MR and LIM1215-MR) and one by human CRC cells harboring KRAS mutation (HCT116-MR) showed features related to the gene signature of colorectal cancer CMS4 with up-regulation of immune pathway as confirmed by microarray and western blot analysis. In particular, the MEKi phenotype was associated with the loss of epithelial features and acquisition of mesenchymal markers and morphology. The change in morphology was accompanied by up-regulation of PD-L1 expression and activation of EGFR and its downstream pathway, independently to RAS mutation status. To extend these in vitro findings, we have obtained mouse colon cancer MC38- and CT26-MEKi resistant syngeneic models (MC38-MR and CT26-MR). Combined treatment with MEKi, EGFR inhibitor (EGFRi) and PD-L1 inhibitor (PD-L1i) resulted in a marked inhibition of tumor growth in both models.

CONCLUSIONS

These results suggest a strategy to potentially improve the efficacy of MEK inhibition by co-treatment with EGFR and PD-L1 inhibitors via modulation of host immune responses.

Anti-EGFR-resistant clones decay exponentially after progression: implications for anti-EGFR re-challenge

BACKGROUND

Colorectal cancer (CRC) has been shown to acquire RAS and EGFR ectodomain mutations as mechanisms of resistance to epidermal growth factor receptor (EGFR) inhibition (anti-EGFR). After anti-EGFR withdrawal, RAS and EGFR mutant clones lack a growth advantage relative to other clones and decay; however, the kinetics of decay remain unclear. We sought to determine the kinetics of acquired RAS/EGFR mutations after discontinuation of anti-EGFR therapy.

PATIENTS AND METHODS

We present the post-progression circulating tumor DNA (ctDNA) profiles of 135 patients with RAS/BRAF wild-type metastatic CRC treated with anti-EGFR who acquired RAS and/or EGFR mutations during therapy. Our validation cohort consisted of an external dataset of 73 patients with a ctDNA profile suggestive of prior anti-EGFR exposure and serial sampling. A separate retrospective cohort of 80 patients was used to evaluate overall response rate and progression free survival during re-challenge therapies.

RESULTS

Our analysis showed that RAS and EGFR relative mutant allele frequency decays exponentially (r2=0.93 for RAS; r2=0.94 for EGFR) with a cumulative half-life of 4.4 months. We validated our findings using an external dataset of 73 patients with a ctDNA profile suggestive of prior anti-EGFR exposure and serial sampling, confirming exponential decay with an estimated half-life of 4.3 months. A separate retrospective cohort of 80 patients showed that patients had a higher overall response rate during re-challenge therapies after increasing time intervals, as predicted by our model.

CONCLUSION

These results provide scientific support for anti-EGFR re-challenge and guide the optimal timing of re-challenge initiation.

It is finally time for adjuvant therapy in melanoma

Although melanoma is amenable to early detection, there has been no decline in the mortality rate of this disease and the prognosis of patients with high-risk primary melanoma or with macroscopic nodal involvement remains poor. The best option for patients with higher-risk melanoma is to receive effective adjuvant therapy in order to reduce their chances of recurrence. Multiple systemic therapeutic agents have been tested as adjuvant therapy for melanoma with durable benefits seen only with interferon- to date. More recently ipilimumab at the high dose of 10 mg/kg has shown a significant improvement in terms of Relapse free survival and Overall survival for stage III melanoma patients but at a significant cost in terms of immune-related toxicities. More recently, novel treatment options have emerged. The results from the latest trials with immunotherapy (PD-1 inhibitors) and molecular targeted therapy (BRAF inhibitor + MEK inhibitor) have revolutionized the management of adjuvant treatment for melanoma. As the results from these trials will mature in the next years, a change in the landscape of adjuvant treatment for melanoma is expected, resulting in new challenges in treatment decisions such as optimizing patients' selection through predictive and prognostic biomarkers, and management of treatment related adverse events, in particular immune related toxicities.

Recurrent esophageal stricture from previous caustic ingestion treated with 40-year self-dilation: case report and review of literature

Background

Corrosive esophageal strictures are common. The severity of the strictures depends on type, quantity, duration of contact and concentration of the caustic substance ingested. Endoscopic balloon dilation and endoscopic bougienage are a cornerstone in the management of the benign esophageal strictures and are the most widely used treatments, but are expensive and invasive procedures.

Case Presentation

We report the case of an 82-year-old patient with a corrosive esophageal stricture treated for over 40 years by means of home self-bougienage. The procedure has been carried out for the longest lapse of time described in literature, with an excellent control of symptoms. In the case reported, after being carried out for more than 40 years, self-dilation allowed good quality of life and symptoms management, ensuring an excellent nutritional status.

Conclusions

Following an adequate patient training, self-dilatation can be a safe and effective option of treatment, avoiding frequent expensive hospital admissions for endoscopic esophageal dilatation.

Unintentional recurrent laryngeal nerve injuries following thyroidectomy: Is it the surgeon who pays the bill?

BACKGROUND

Thyroidectomy is one of the most common intervention in general surgery and, after the turn of the century, its rate has sharply increased, along with a worldwide increased incidence of differentiated thyroid cancers. Therefore, injuries of the recurrent laryngeal nerve have become one of the most frequent cause of surgical malpractice claims, mostly following surgery for benign pathology.

MAIN BODY

Even if the incidence of definitive paralysis is generally lower than 3%, during the last 20 years in Italy, the number of claims for damages has sharply raised. As a consequence, a lot of defensive medicine has been caused by this issue, and a witch-hunt has been accordingly triggered, so determining mostly a painful and lasting frustration for the surgeons, who sometimes are compelled to pay a lot of money for increasing insurance premiums and lawyers fees. Recurrent laryngeal nerve injury should be considered as a potentially catastrophic predictable but not preventable event, rather than the result of a surgical mistake.

CONCLUSION

Purposes of the Authors are analyzing incidence, conditions of risk, and mechanisms of recurrent laryngeal nerve injuries, underlining notes of surgical technique and defining medical practice recommendations useful to reduce the risk of malpractice lawsuits and judgments against surgeons.

Clinical significance of prophylactic central compartment neck dissection in the treatment of clinically node-negative papillary thyroid cancer patients

Background

Lymph nodal involvement is very common in differentiated thyroid cancer, and in addition, cervical lymph node micrometastases are observed in up to 80 % of papillary thyroid cancers. During the last decades, the role of routine central lymph node dissection (RCLD) in the treatment of papillary thyroid cancer (PTC) has been an object of research, and it is now still controversial. Nevertheless, many scientific societies and referral authors have definitely stated that even if in expert hands, RCLD is not associated to higher morbidity; it should be indicated only in selected cases.

Main body

In order to better analyze the current role of prophylactic neck dissection in the surgical treatment of papillary thyroid cancers, an analysis of the most recent literature data was performed. Prophylactic or therapeutic lymph node dissection, selective, lateral or central lymph node dissection, modified radical neck dissection, and papillary thyroid cancer were used by the authors as keywords performing a PubMed database research. Literature reviews, PTCs large clinical series and the most recent guidelines of different referral endocrine societies, inhering neck dissection for papillary thyroid cancers, were also specifically evaluated. A higher PTC incidence was nowadays reported in differentiated thyroid cancer (DTC) clinical series. In addition, ultrasound guided fine-needle aspiration citology allowed a more precocious diagnosis in the early phases of disease. The role of prophylactic neck dissection in papillary thyroid cancer management remains controversial especially regarding indications, approach, and surgical extension. Even if morbidity rates seem to be similar to those reported after total thyroidectomy alone, RCLD impact on local recurrence and long-term survival is still a matter of research. Nevertheless, only a selective use in high-risk cases is supported by more and more scientific data.

Conclusions

In the last years, higher papillary thyroid cancer incidence and more precocious diagnoses were worldwide reported. Among endocrine and neck surgeons, there is agreement about indications to prophylactic treatment of node-negative “high-risk” patients. A recent trend toward RCLD avoiding radioactive treatment is still debated, but nevertheless, prophylactic dissections in low-risk cases should be avoided. Prospective randomized trials are needed to evaluate the benefits of different approaches and allow to drawn definitive conclusions.

The current status of lymph node dissection in the treatment of papillary thyroid cancer. A literature review

AIM

Cervical lymph node micrometastases are observed in up to 90% of papillary thyroid cancers (PTC), showing that lymph nodal involvement is very common. Nevertheless, during the last years, the role of lymph node dissection in the treatment of PTC has been controversial and, at present, the best indications to the routine or therapeutic neck dissection remain subject of research. In order to better analyze the current role of lymph node dissection in the surgical treatment of PTC, an analysis of the most recent literature data was performed.

STUDY DESIGN

By using as keywords lymph node dissection, selective, lateral or central lymph node dissection, modified radical neck dissection, prophylactic or therapeutic lymph node dissection, papillary thyroid cancer, a Pub Med data base research was carried out. The most recent guidelines of different referral endocrine societies, inhering neck dissection for PTC, were also evaluated.

RESULTS

The role of neck dissection in PTC management remains controversial regarding routine or therapeutic indications, surgical extension, and its impact on local recurrence and long term survival. Due to inhomogeneous literature data, the current status of node dissection is still subject of research.

CONCLUSIONS

There is agreement between endocrine and neck surgeons about the extension of therapeutic lymph node dissection in N+ PTC patients , and also in the prophylactic treatment of N0 "high risk" patients. Considering a recent trend toward routine central lymphadenectomy avoiding radioactive treatment, prospective randomized trials are needed to evaluate the benefits of different approaches.

Conservative management and parenchyma-sparing resections of pancreatic neuroendocrine tumors: Literature review

BACKGROUND

Pancreatic neuroendocrine tumors (pNETs) are uncommon entities. pNETs are often small, slow growing, clinically silent neoplasms. However, they have an almost unpredictable biological behaviour with a not negligible malignant potential. Surgery still represents the treatment of choice, but the high morbidity associated to the enucleation or the formal pancreatectomy should be considered in the decision of the proper treatment. Management of these neoplasms is still debated, and indications for a conservative observational approach and for parenchyma sparing resections are not yet standardized.

METHOD

We review the state of art on the indications for the conservative management of pNETs. Searches on MEDLINE database were performed to identify articles reporting prognostic systems, biochemical screening, observational management, medical treatment and surgical strategies for pNETs.

DISCUSSION

Currently, an accurate 'wait-and-see' policy is recommended by the European Neuroendocrine Tumor Society (ENETS) only for non-functioning pNETs (NF-pNETs) <2 cm. A biochemical screening, based on sampling of serum levels of pancreatic polypeptide (PP) and chromogranin A, can address to early conservative surgery for MEN-1 associated NF-pNETs <2 cm to prevent their malignant transformation. The subtotal (80%) distal pancreatectomy first proposed by Thompson, often with the enucleation of possible pancreatic head tumors, still represents a good compromise between oncological radicality and prevention of pancreatic endocrine/exocrine insufficiency caused by standard radical resections for the treatment of inherited syndromes associated with NF-pNETs >2 cm and symptomatic F-pNETs of any size.

CONCLUSION

More studies are needed to further clarify and predict the biologic behaviour of pNETs and increase the indications for conservative observational management and parenchyma sparing pancreas resections.

Molecular aspects of resistance to biological and non-biological drugs and strategies to overcome resistance in colorectal cancer

A number of successful systemic therapies are available for the treatment of disseminated cancers. However, tumor response is often transient, and therapy frequently fails due to emergence of resistant populations. The latter reflects the temporal and spatial heterogeneity of the tumor microenvironment as well as the evolutionary capacity of cancer phenotypes to adapt to therapeutic perturbations. Resistance to either chemotherapy and targeted agents limits the effectiveness of current cancer therapies, including those used to treat metastatic colorectal cancer (mCRC) which is one of the leading causes of cancer-related death worldwide. Resistance to therapeutic drugs can be already present at diagnosis or it can develop after treatment. These two forms of resistance are respectively called intrinsic and acquired. The identification of mechanisms of drug resistance may highlight new biomarkers useful to predict the clinical outcome or the likely responsiveness to pharmacological treatment of those metastatic CRC patients who cannot benefit from current therapeutic regimen. Moreover, the recognition of panels of biomarkers may suggest new strategies to overcome resistance by rational drug design and combination treatment. In this review, we describe molecular mechanisms of resistance to chemotherapies and targeted agents that may be relevant to colorectal cancer and the possible strategies to overcome the resistance.