Does dose reduction of afatinib affect treatment outcomes of patients with EGFR-mutant metastatic non-small cell lung cancer in real-world clinical practice?

Background: Afatinib can be started at a dose lower than the recommended starting dose of 40 mg/day for the treatment of epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC), however treatment outcomes in real-world clinical practice remains unclear. Methods: This retrospective study of patients with NSCLC from 18 major hospitals (public, private or university teaching hospitals) enrolled in Malaysia's National Cardiovascular and Thoracic Surgical Database (NCTSD) assessed the efficacy of lower doses of afatinib on treatment outcomes in a real-world clinical practice. Data on clinical characteristics, afatinib dosing, and treatment outcomes for patients included in NCTSD from 1st January 2015 to 31st December 2020 were analyzed. Results: Of the 133 patients studied, 94.7% had adenocarcinoma. Majority of the patients (60.9%) had EGFR exon 19 deletion and 23.3% had EGFR exon 21 L858R point mutation. The mean age of patients was 64.1 years and majority (83.5%) had Eastern Cooperative Oncology Group performance status of 2-4 at diagnosis. The most common afatinib starting doses were 40 mg (37.6%), 30 mg (29.3%), and 20 mg (26.3%) once daily (OD), respectively. A quarter of patients had dose reduction (23.3%) due to side effects or cost constraints. Majority of the patients had partial response to afatinib (63.2%) whilst 2.3% had complete response. Interestingly, the objective response rate was significantly higher (72.3%) with afatinib OD doses of less than 40 mg compared to 40 mg (54.0%) (P=0.032). Patients on lower doses of afatinib were two times more likely to achieve an objective response [odds ratio =2.64; 95% confidence interval (CI): 1.20-5.83; P=0.016]. These patients had a numerically but not statistically longer median time to treatment failure (TTF). Median TTF (95% CI) for the overall cohort was 12.4 (10.02-14.78) months. Median overall survival (95% CI) was 21.30 (15.86-26.75) months. Conclusions: Lower afatinib doses (<40 mg OD) could be equally effective as standard dose in patients with EGFR-mutant advanced NSCLC and may be more suited to Asian patients, minimizing side effects that may occur at higher dosages of afatinib leading to dose interruptions and affecting treatment outcomes.

Real-World Treatment and Outcomes of ALK-Positive Metastatic Non-Small Cell Lung Cancer in a Southeast Asian Country.

Purpose: Anaplastic lymphoma kinase (ALK) inhibitors are associated with good overall survival (OS) for ALK-positive metastatic non-small cell lung cancer (NSCLC). However, these treatments can be unavailable or limited by financial constraints in developing countries. Using data from a nationwide lung cancer registry, the present study aimed to identify treatment patterns and clinical outcomes of ALK-positive NSCLC in Malaysia. Methods: This retrospective study examined data of patients with ALK-positive NSCLC from 18 major hospitals (public, private, or university teaching hospitals) throughout Malaysia between January 1, 2015 and December 31, 2020 from the National Cardiovascular and Thoracic Surgical Database (NCTSD). Data on baseline characteristics, treatments, radiological findings, and pathological findings were collected. Overall survival (OS) and time on treatment (TOT) were calculated using the Kaplan-Meier method. Results: There were 1581 NSCLC patients in the NCTSD. Based on ALK gene-rearrangement test results, only 65 patients (4.1%) had ALK-positive advanced NSCLC. Of these 65 patients, 59 received standard-of-care treatment and were included in the analysis. Crizotinib was the most commonly prescribed ALK inhibitor, followed by alectinib and ceritinib. Patients on ALK inhibitors had better median OS (62 months for first-generation inhibitors, not reached at time of analysis for second-generation inhibitors) compared to chemotherapy (27 months), but this was not statistically significant (P=0.835) due to sample-size limitations. Patients who received ALK inhibitors as first-line therapy had significantly longer TOT (median of 11 months for first-generation inhibitors, not reached for second-generation inhibitors at the time of analysis) compared to chemotherapy (median of 2 months; P<0.01). Conclusion: Patients on ALK inhibitors had longer median OS and significantly longer TOT compared to chemotherapy, suggesting long-term benefit.

Analytical and clinical validation of a custom 15-gene next-generation sequencing panel for the evaluation of circulating tumor DNA mutations in patients with advanced non-small-cell lung cancer.

BACKGROUND: This is a pilot proof-of-concept study to evaluate the utility of a custom 15-gene circulating tumor DNA (ctDNA) panel as a potential companion molecular next-generation sequencing (NGS) assay for identifying somatic single nucleotide variants and indels in non-small-cell lung cancer (NSCLC) patients. The custom panel covers the hotspot mutations in EGFR, KRAS, NRAS, BRAF, PIK3CA, ERBB2, MET, KIT, PDGFRA, ALK, ROS1, RET, NTRK1, NTRK2 and NTRK3 genes which serve as biomarkers for guiding treatment decisions in NSCLC patients. METHOD: The custom 15-gene ctDNA NGS panel was designed using ArcherDX Assay Designer. A total of 20 ng or 50 ng input ctDNA was used to construct the libraries. The analytical performance was evaluated using reference standards at different allellic frequencies (0.1%, 1%, 5% and parental). The clinical performance was evaluated using plasma samples collected from 10 treatment naïve advanced stage III or IV NSCLC patients who were tested for tissue EGFR mutations. The bioinformatics analysis was performed using the proprietary Archer Analysis Software. RESULTS: For the analytical validation, we achieved 100% sensitivity and specificity for the detection of known mutations in the reference standards. The limit of detection was 1% allelic frequency. Clinical validation showed that the clinical sensitivity and specificity of the assay for detecting EGFR mutation were 83.3% and 100% respectively. In addition, the NGS panel also detected other mutations of uncertain significance in 6 out of 10 patients. CONCLUSION: This preliminary analysis showed that the custom 15-gene ctDNA NGS panel demonstrated good analytical and clinical performances for the EGFR mutation. Further studies incorporating the validation of other candidate gene mutations are warranted.

Outcomes of Patients with EGFR-Mutant Advanced NSCLC in a Developing Country in Southeast Asia.

Background: Although first- and second-generation EGFR TKIs are considered first-line treatment in EGFRm+ NSCLC, most patients develop resistance and progress, commonly, EGFR T790M mutation. The third-generation EGFR-TKI has demonstrated efficacy in patients with progressive disease harboring the T790M mutation and in the first-line setting, bypassing this mode of resistance. The primary objectives of this study are to describe the proportion of EGFRm+ NSCLC patients treated with first-, second- and third-generation EGFR TKIs, and cytotoxic chemotherapy in the first-line setting, and the time on treatment for each category. Secondary objectives are to determine the dropout rate, the rates for T790M mutation testing at disease progression and the type of subsequent treatment. Methods: This multicenter retrospective study utilized data from the Malaysian Lung Cancer Registry that actively registers all lung cancer patients ≥18 years, with primary lung cancer confirmed histologically or cytologically. All patients diagnosed with advanced stages (ie stages IIIB, IIIC and IV) EGFRm+ NSCLC from 1st of January 2015 to 31st December 2019 were included. Results: Of 406 patients with EGFRm+ NCSLC, 351 were treated. Types of first-line treatment were as follows: EGFR-TKIs (first generation - 54.1%, second generation - 25.6% and third-generation - 12.5%) and chemotherapy (7.7%). The median time of treatment for each generation of EGFR-TKI was 12 months, 12 months and 24 months, and 2 months for chemotherapy. The dropout rate was 28.7% (n = 101). Nearly half (49.4%) of patients who were on first- or second-generation EGFR-TKI had further genetic testing via liquid or tissue biopsies upon disease progression. About 24.9% of those who developed disease progression after first- or second-generation EGFR TKI were started on a third-generation EGFR TKI. Conclusion: In the real-world, the management of EGFRm+ advanced NSCLC patients in an Asian cost-restrictive setting may adversely affect the choice of first-line therapy, time on each line of treatment and subsequently the overall survival of patients.

Programmed death-ligand 1 expression and use of immune checkpoint inhibitors among patients with advanced non-small-cell lung cancer in a resource-limited country.

INTRODUCTION: Immune checkpoint inhibitor (ICI) therapy is an established treatment for advanced non-small-cell lung cancer (NSCLC) and programmed death ligand-1 (PD-L1) expression is a recognized biomarker to determine response to therapy. We retrospectively analyzed NSCLC patients in the Malaysia Lung Cancer Registry (MLCR) and report on the clinical characteristics associated with PD-L1 expression and ICI use in Malaysia, a low- to middle-income country. METHODS: All 901 NSCLC patients in the MLCR who were diagnosed from January 1, 2017 to December 31, 2020 from 14 hospitals across the country were analyzed. RESULTS: Out of 901 patients, 505 had PDL-1 testing done with complete data available only in 489 patients. The most common histology was adenocarcinoma (84.7%) followed by squamous cell carcinoma (10.2%). The majority (95%) presented with stage 3 or 4. The number and percentage of patients with PDL-1 tumor proportion scores of ≥50%, 1-49%, and <1% were 138 (28.2%), 158 (32.3%), and 193 (39.5%), respectively. In multivariate analysis, the presence of genomic mutation is the only independent characteristic associated with negative PD-L1 expression (crude odds ratio 0.579, 95% confidence interval 0.399-0.840, p = 0.004). Of 292 patients eligible for ICI therapy, only 100 patients (34.2%) received ICIs. Seventy-eight patients received ICI therapy as first-line treatment, 15 patients as second-line treatment, and 7 patients as third-line treatment. CONCLUSIONS: This is the first analysis on PD-L1 expression and ICI use in Malaysia. Despite the proven efficacy of ICI therapy, only 56% of our patients had PD-L1 tests performed and only 34.2% of eligible patients received ICIs.

Morphine use for cancer pain: A strong analgesic used only at the end of life? A qualitative study on attitudes and perceptions of morphine in patients with advanced cancer and their caregivers.

BACKGROUND: The prevalence of undertreated cancer pain remains high. Suboptimal pain control affects quality of life and results in psychological and emotional distress. Barriers to adequate pain control include fear of opioid dependence and its side effects. AIM: To investigate the attitudes and perceptions of morphine use in cancer pain in advanced cancer patients and their caregivers and to examine the influence of caregivers' attitudes and perceptions on patients' acceptance of morphine. DESIGN: Qualitative study involving semi-structured individual interviews transcribed verbatim and analyzed thematically. SETTING/PARTICIPANTS: A total of 18 adult opioid-naïve patients with advanced cancer and 13 caregivers (n = 31) were recruited at a private tertiary hospital via convenience sampling. RESULTS: Attitudes and perceptions of morphine were influenced by previous experiences. Prevalent themes were similar in both groups, including perceptions that morphine was a strong analgesic that reduced suffering, but associated with end-stage illness and dependence. Most participants were open to future morphine use for comfort and effective pain control. Trust in doctors' recommendations was also an important factor. However, many preferred morphine as a last resort because of concerns about side effects and dependence, and the perception that morphine was only used at the terminal stage. Caregivers' attitudes toward morphine did not affect patients' acceptance of morphine use. CONCLUSION: Most participants were open to future morphine use despite negative perceptions as they prioritized optimal pain control and reduction of suffering. Focused education programs addressing morphine misperceptions might increase patient and caregiver acceptance of opioid analgesics and improve cancer pain control.

Asian Thoracic Oncology Research Group Expert Consensus Statement on Optimal Management of Stage III NSCLC.

Stage III NSCLC represents a heterogeneous disease for which optimal treatment continues to pose a clinical challenge. Recent changes in the American Joint Commission on Cancer staging to the eighth edition has led to a shift in TNM stage grouping and redefined the subcategories (IIIA-C) in stage III NSCLC for better prognostication. Although concurrent chemoradiotherapy has remained standard-of-care for stage III NSCLC for almost 2 decades, contemporary considerations include the impact of different molecular subsets of NSCLC, and the roles of tyrosine kinase inhibitors post-definitive therapy and of immune checkpoint inhibitors following chemoradiotherapy. With rapid evolution of diagnostic algorithms and expanding treatment options, the need for interdisciplinary input involving multiple specialists (medical oncologists, radiation oncologists, pulmonologists, radiologists, pathologists and thoracic surgeons) has become increasingly important. The unique demographics of Asian NSCLC pose further challenges when applying clinical trial data into clinical practice. This includes differences in smoking rates, prevalence of oncogenic driver mutations, and access to health care resources including molecular testing, prompting the need for critical review of existing data and identification of current gaps. In this expert consensus statement by the Asian Thoracic Oncology Research Group, an interdisciplinary group of experts representing Hong Kong, Korea, Japan, Taiwan, Singapore, Thailand, Malaysia, and Mainland China was convened. Standard clinical practices for stage III NSCLC across different Asian countries were discussed from initial diagnosis and staging through to multi-modality approaches including surgery, chemotherapy, radiation, targeted therapies, and immunotherapy.

Molecular testing for advanced non-small cell lung cancer in Malaysia: Consensus statement from the College of Pathologists, Academy of Medicine Malaysia, the Malaysian Thoracic Society, and the Malaysian Oncological Society.

In the recent years, increased understanding of the molecular profiles of non-small cell lung cancer (NSCLC) has allowed for targeted treatment of actionable genetic mutations. The management of NSCLC now requires multiple molecular tests to guide the treatment strategy. In the light of this, there is a need to establish a molecular testing consensus statement for advanced NSCLC patients in Malaysia. This Malaysian consensus statement was developed by a panel of experts, chaired by a pathologist and composed of three other pathologists, four respiratory physicians and three oncologists. It reflects currently available scientific data and adaptations of recommendations from international guidelines to the local landscape. Expert recommendations on different aspects of molecular testing agreed upon by the panel are provided as structured discussions. These recommendations address the appropriate patients and samples to be tested, as well as when and how these tests should be performed. The algorithms for molecular testing in metastatic NSCLC, in the first line setting and upon disease progression beyond first line therapy, were developed.

Inadequate treatment practices for pain relief and adverse event management in cancer patients across 10 countries/regions in Asia: a call for greater efforts to improve standards for patient care.

AIM: To examine the treatment practices for cancer pain relief and adverse event management, and the factors related to patient outcomes in the participating countries/regions. METHODS: The study was a cross-sectional survey conducted between September and December 2013 in 10 countries/regions across Asia. Adult patients with a history of cancer pain at least 1 month before study entry completed the survey questionnaire. RESULTS: A total of 1190 patients were included. The mean Box Scale-11 (BS-11) pain score was 6.0 (SD 2.1), with 86.2% experiencing moderate-to-severe pain and 53.2% receiving opioids at time of the survey. The mean BS-11 scores were 5.3 (SD 2.1) in the "others" (single non-opioid medication or untreated) group, 6.3 (SD 2.0) in the ≥2 non-opioids group and 6.7 (SD 1.9) in the opioid group. The proportions of patients experiencing moderate-to-severe pain were 79.1%, 87.3% and 93.7%, respectively. About 70% of patients reported adverse events due to their pain medications, about half had received medications to manage these symptoms. Adverse events were negatively associated with activities of daily living (P < 0.0001). Pain and hindrance to activities of daily living were negatively associated with employment status (P = 0.003 and 0.021). Unemployment was significantly associated with poorer quality of life (P < 0.0001). CONCLUSION: This analysis demonstrates inadequate management of cancer pain and treatment-related adverse events in the participating cohort. Pain and inadequate management of adverse events were negatively associated with patients' overall well-being. More collaborative efforts should be taken to optimize pain treatment and increase awareness of adverse event management in physicians.

Current practices in cancer pain management in Asia: a survey of patients and physicians across 10 countries.

In order to implement more effective policies for cancer pain management, a better understanding of current practices is needed. Physicians managing cancer pain and patients experiencing cancer pain were randomly surveyed across 10 Asian countries to assess attitudes and perceptions toward cancer pain management. A total of 463 physicians (77.3% oncologists) with a median experience of 13 years were included. Medical school training on opioid use was considered inadequate by 30.5% of physicians and 55.9% indicated ≤ 10 h of continuing medical education (CME). Of the 1190 patients included, 1026 reported moderate-to-severe pain (median duration, 12 months). Discordance was observed between physician and patient outcomes on pain assessment with 88.3% of physicians reporting pain quantification, while 49.5% of patients claimed that no scale was used. Inadequate assessment of pain was recognized as a barrier to therapy optimization by 49.7% of physicians. Additional barriers identified were patients' reluctance owing to fear of addiction (67.2%) and adverse events (65.0%), patients' reluctance to report pain (52.5%), excessive regulations (48.0%) and reluctance to prescribe opioids (42.8%). Opioid use was confirmed only in 53.2% (286/538) of patients remembering their medication. Pain affected the activities of daily living for 81.3% of patients. These findings highlight the need for better training and CME opportunities for cancer pain management in Asia. Collaborative efforts between physicians, patients, policy makers, and related parties may assist in overcoming the barriers identified. Addressing the opioid stigma and enhancing awareness is vital to improving current standards of patient care.

Prognostic factors in patients with non-small cell lung carcinoma and brain metastases: a Malaysian perspective.

BACKGROUND: Brain metastases occur in about 20-40% of patients with non-small-cell lung carcinoma (NSCLC), and are usually associated with a poor outcome. Whole brain radiotherapy (WBRT) is widely used but increasingly, more aggressive local treatments such as surgery or stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) are being employed. In our study we aimed to describe the various factors affecting outcomes in NSCLC patients receiving local therapy for brain metastases. MATERIALS AND METHODS: The case records of 125 patients with NSCLC and brain metastases consecutively treated with radiotherapy at two tertiary centres from January 2006 to June 2012 were analysed for patient, tumour and treatment-related prognostic factors. Patients receiving SRS/SRT were treated using Cyberknife. Variables were examined in univariate and multivariate testing. RESULTS: Overall median survival was 3.4 months (95%CI: 1.7-5.1). Median survival for patients with multiple metastases receiving WBRT was 1.5 months, 1-3 metastases receiving WBRT was 3.6 months and 1-3 metastases receiving surgery or SRS/SRT was 8.9 months. ECOG score (≤2 vs >2, p=0.001), presence of seizure (yes versus no, p=0.031), treatment modality according to number of brain metastases (1-3 metastases+surgery or SRS/SRT±WBRT vs 1-3 metastases+WBRT only vs multiple metastases+WBRT only, p=0.007) and the use of post-therapy systemic treatment (yes versus no, p=0.001) emerged as significant on univariate analysis. All four factors remained statistically significant on multivariate analysis. CONCLUSIONS: ECOG ≤2, presence of seizures, oligometastatic disease treated with aggressive local therapy (surgery or SRS/SRT) and the use of post-therapy systemic treatment are favourable prognostic factors in NSCLC patients with brain metastases.

Treatment outcome for nasopharyngeal carcinoma in University Malaya Medical Centre from 2004-2008.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is the commonest radiocurable cancer in Malaysia. This study aimed to determine the treatment outcomes and late effects of radiotherapy for NPC patients treated in University Malaya Medical Centre (UMMC). MATERIALS AND METHODS: All newly diagnosed patients with NPC referred for treatment to the Oncology unit at UMMC from 2004-2008 were retrospectively analyzed. Treatment outcomes were 5 years overall survival (OS), disease free survival (DFS), cause-specific survival (CSS), loco- regional control (LRC) and radiotherapy-related late effects. The Kaplan-Meier method was used for survival analysis and differences in survival according to AJCC stage was compared using the log-rank test. RESULTS: A total of 176 patients with newly diagnosed NPC were treated in UMMC during this period. Late presentation was common, with 33.5% presenting with T3-4 disease, 84.7% with N1-3 disease and 75.6% with AJCC stage 3-4 disease. Radical RT was given to 162 patients with 22.7% having RT alone and 69.3% having CCRT. The stipulated OTT was 7 weeks and 72.2% managed to complete their RT within this time period. Neoadjuvant chemotherapy was given to 14.8% while adjuvant chemotherapy was administered to 16.5%. The 5 years OS was 51.6% with a median follow up of 58 months. The 5 years OS according to stage were 81.8% for stage I, 77.9% for stage II, 47.4% for stage III and 25.9% for stage IV. The 5 years overall CSS, DFS and LRC were 54.4%, 48.4% and 70.6%, respectively. RT related late effects were documented in 80.2%. The commonest was xerostomia (66.7%). Other documented late effects were hearing deficit (17.3%), visual deficit (3.1%), neck stiffness (3.1%) , dysphagia (3.4%), cranial nerve palsy (2.5%), pneumonitis (0.6%) and hypothyroidism (1.2%). CONCLUSIONS: The 5 years OS and LRC in this study are low compared to the latest studies especially those utilizing IMRT. Implementation of IMRT for NPC treatment should be strongly encouraged.

Efficacy of temsirolimus in metastatic chromophobe renal cell carcinoma.

BACKGROUND: Renal cell carcinoma (RCC) is a histopathologically and molecularly heterogeneous disease with the chromophobe subtype (chRCC) accounting for approximately 5% of all cases. The median overall survival of advanced RCC has improved significantly since the advent of tyrosine kinase inhibitors and mammalian target of rapamycin (mTOR) inhibitors. However, high-quality evidence for the use of new generation tyrosine kinase inhibitors in patients with advanced chRCC is lacking. Few published case reports have highlighted the use of temsirolimus in chRCC. CASE PRESENTATION: Here, we report the case of a 36-year-old Caucasian woman with metastatic chRCC with predominantly skeletal metastases who was refractory to sunitinib who demonstrated a durable clinical response to temsirolimus lasting 20 months. We review the available evidence pertaining to the use of new generation molecularly targeted agents, in particular mTOR inhibitors in chRCC and discuss their emerging role in the management of this disease which would aid the oncologists faced with the challenge of treating this rare type of RCC. CONCLUSION: Conducting randomised clinical trials in this rarer sub-group of patients would be challenging and our case report and the evidence reviewed would guide the physicians to make informed decision regarding the management of these patients.

The influence of MRI scan position on patients with oropharyngeal cancer undergoing radical radiotherapy.

BACKGROUND: The purpose of this study was to demonstrate how magnetic resonance imaging (MRI) patient position protocols influence registration quality in patients with oropharyngeal cancer undergoing radical radiotherapy and the consequences for gross tumour volume (GTV) definition and radiotherapy planning. METHODS AND MATERIALS: Twenty-two oropharyngeal patients underwent a computed tomography (CT), a diagnostic MRI (MRI(D)) and an MRI in the radiotherapy position within an immobilization mask (MRI(RT)). Clinicians delineated the GTV on the CT viewing the MRI(D) separately (GTV(C)); on the CT registered to MRI(D) (GTV(D)) and on the CT registered to MRI(RT) (GTV(RT)). Planning target volumes (PTVs) were denoted similarly. Registration quality was assessed by measuring disparity between structures in the three set-ups. Volumetric modulated arc therapy (VMAT) radiotherapy planning was performed for PTV(C), PTV(D) and PTV(RT). To determine the dose received by the reference PTV(RT), we optimized for PTV(C) and PTV(D) while calculating the dose to PTV(RT). Statistical significance was determined using the two-tailed Mann-Whitney or two-tailed paired student t-tests. RESULTS: A significant improvement in registration accuracy was found between CT and MRI(RT) versus the MRI(D) measuring distances from the centre of structures (geometric mean error of 2.2 mm versus 6.6 mm). The mean GTV(C) (44.1 cm3) was significantly larger than GTV(D) (33.7 cm3, p value = 0.027) or GTV(RT) (30.5 cm3, p value = 0.014). When optimizing the VMAT plans for PTV(C) and investigating the mean dose to PTV(RT) neither the dose to 99% (58.8%) nor 95% of the PTV (84.7%) were found to meet the required clinical dose constraints of 90% and 95% respectively. Similarly, when optimizing for PTV(D) the mean dose to PTV(RT) did not meet clinical dose constraints for 99% (14.9%) nor 95% of the PTV (66.2%). Only by optimizing for PTV(RT) were all clinical dose constraints achieved. CONCLUSIONS: When oropharyngeal patients MRI scans are performed in the radiotherapy position there are significant improvements in CT-MR image registration, target definition and PTV dose coverage.

The ATM-Chk2 and ATR-Chk1 pathways in DNA damage signaling and cancer.

DNA damage is a key factor both in the evolution and treatment of cancer. Genomic instability is a common feature of cancer cells, fuelling accumulation of oncogenic mutations, while radiation and diverse genotoxic agents remain important, if imperfect, therapeutic modalities. Cellular responses to DNA damage are coordinated primarily by two distinct kinase signaling cascades, the ATM-Chk2 and ATR-Chk1 pathways, which are activated by DNA double-strand breaks (DSBs) and single-stranded DNA respectively. Historically, these pathways were thought to act in parallel with overlapping functions; however, more recently it has become apparent that their relationship is more complex. In response to DSBs, ATM is required both for ATR-Chk1 activation and to initiate DNA repair via homologous recombination (HRR) by promoting formation of single-stranded DNA at sites of damage through nucleolytic resection. Interestingly, cells and organisms survive with mutations in ATM or other components required for HRR, such as BRCA1 and BRCA2, but at the cost of genomic instability and cancer predisposition. By contrast, the ATR-Chk1 pathway is the principal direct effector of the DNA damage and replication checkpoints and, as such, is essential for the survival of many, although not all, cell types. Remarkably, deficiency for HRR in BRCA1- and BRCA2-deficient tumors confers sensitivity to cisplatin and inhibitors of poly(ADP-ribose) polymerase (PARP), an enzyme required for repair of endogenous DNA damage. In addition, suppressing DNA damage and replication checkpoint responses by inhibiting Chk1 can enhance tumor cell killing by diverse genotoxic agents. Here, we review current understanding of the organization and functions of the ATM-Chk2 and ATR-Chk1 pathways and the prospects for targeting DNA damage signaling processes for therapeutic purposes.

Acute small bowel toxicity and preoperative chemoradiotherapy for rectal cancer: investigating dose-volume relationships and role for inverse planning.

PURPOSE: The relationship between volume of irradiated small bowel (VSB) and acute toxicity in rectal cancer radiotherapy is poorly quantified, particularly in patients receiving concurrent preoperative chemoradiotherapy. Using treatment planning data, we studied a series of such patients. METHODS AND MATERIALS: Details of 41 patients with locally advanced rectal cancer were reviewed. All received 45 Gy in 25 fractions over 5 weeks, 3-4 fields three-dimensional conformal radiotherapy with daily 5-fluorouracil and folinic acid during Weeks 1 and 5. Toxicity was assessed prospectively in a weekly clinic. Using computed tomography planning software, the VSB was determined at 5 Gy dose intervals (V5, V10, etc.). Eight patients with maximal VSB had dosimetry and radiobiological modeling outcomes compared between inverse and conformal three-dimensional planning. RESULTS: VSB correlated strongly with diarrheal severity at every dose level (p<0.03), with strongest correlation at lowest doses. Median VSB differed significantly between patients experiencing Grade 0-1 and Grade 2-4 diarrhea (p