Clinical Outcomes Associated With Pembrolizumab Monotherapy Among Adults With Diffuse Malignant Peritoneal Mesothelioma

Importance

Diffuse malignant peritoneal mesothelioma (DMPM) represents a rare and clinically distinct entity among malignant mesotheliomas. Pembrolizumab has activity in diffuse pleural mesothelioma but limited data are available for DMPM; thus, DMPM-specific outcome data are needed.

Objective

To evaluate outcomes after the initiation of pembrolizumab monotherapy in the treatment of adults with DMPM.

Design, Setting, and Participants

This retrospective cohort study was conducted in 2 tertiary care academic cancer centers (University of Pennsylvania Hospital Abramson Cancer Center and Memorial Sloan Kettering Cancer Center). All patients with DMPM treated between January 1, 2015, and September 1, 2019, were retrospectively identified and followed until January 1, 2021. Statistical analysis was performed between September 2021 and February 2022.

Exposures

Pembrolizumab (200 mg or 2 mg/kg every 21 days).

Main Outcomes and Measures

Median progression-free survival (PFS) and median overall survival (OS) were assessed using Kaplan-Meier estimates. The best overall response was determined using RECIST (Response Evaluation Criteria in Solid Tumors) criteria, version 1.1. The association of disease characteristics with partial response was evaluated using the Fisher exact test.

Results

This study included 24 patients with DMPM who received pembrolizumab monotherapy. Patients had a median age of 62 years (IQR, 52.4-70.6 years); 14 (58.3%) were women, 18 (75.0%) had epithelioid histology, and most (19 [79.2%]) were White. A total of 23 patients (95.8%) received systemic chemotherapy prior to pembrolizumab, and the median number of lines of prior therapy was 2 (range, 0-6 lines). Of the 17 patients who underwent programmed death ligand 1 (PD-L1) testing, 6 (35.3%) had positive tumor PD-L1 expression (range, 1.0%-80.0%). Of the 19 evaluable patients, 4 (21.0%) had a partial response (overall response rate, 21.1% [95% CI, 6.1%-46.6%]), 10 (52.6%) had stable disease, and 5 (26.3%) had progressive disease (5 of 24 patients [20.8%] were lost to follow-up). There was no association between a partial response and the presence of a BAP1 alteration, PD-L1 positivity, or nonepithelioid histology. With a median follow-up of 29.2 (95% CI, 19.3 to not available [NA]) months, the median PFS was 4.9 (95% CI, 2.8-13.3) months and the median OS was 20.9 (95% CI, 10.0 to NA) months from pembrolizumab initiation. Three patients (12.5%) experienced PFS of more than 2 years. Among patients with nonepithelioid vs epithelioid histology, there was a numeric advantage in median PFS (11.5 [95% CI, 2.8 to NA] vs 4.0 [95% CI, 2.8-8.8] months) and median OS (31.8 [95% CI, 8.3 to NA] vs 17.5 [95% CI, 10.0 to NA] months); however, this did not reach statistical significance.

Conclusions and Relevance

The results of this retrospective dual-center cohort study of patients with DMPM suggest that pembrolizumab had clinical activity regardless of PD-L1 status or histology, although patients with nonepithelioid histology may have experienced additional clinical benefit. The partial response rate of 21.0% and median OS of 20.9 months in this cohort with 75.0% epithelioid histology warrants further investigation to identify those most likely to respond to immunotherapy.

Abstract 3474: Molecular subtypes characterize appendiceal adenocarcinoma genomic evolution and disease behavior

Appendiceal adenocarcinoma (AC) are rare gastrointestinal tumors that exhibit a heterogeneous spectrum of tumor histology and differentiation patterns. Personalized AC treatments are limited by the lack of robust histopathological or genomic predictors of disease behavior. We utilized the MSK IMPACT sequencing panel to profile genomic signature patterns in somatic mutations, copy number alterations, and germline mutations in a large curated dataset of patients with AC.

We evaluated co-occurrence and clonality patterns between frequently altered genes in AC (RAS, GNAS, TP53) to establish five molecular subtypes of mucinous appendiceal adenocarcinoma (MAAP): RAS mutated-only, GNAS mutated, TP53 & KRAS mutated, TP53 mutated-only, and none (all wild-type). In multivariable Cox regression models, patients with RAS mutated-only tumors exhibit a nearly non-lethal disease course compared to other molecular subtypes, including TP53 mutated-only tumors (hazard ratio for death: 75.6, p<0.001). Inclusion of tumor molecular subtype in conventional multivariable models improves model prognostic strength. In addition, MAAP-derived molecular subtypes prognosticate patient survival in a separate cohort of 248 patients with right-sided, mismatch-repair-proficient metastatic colorectal cancer.

Molecular characterization of AC also reveals differences in tumor biology and behavior. In addition to an improved prognosis, RAS mutated-only MAAP tumors exhibit significantly lower tumor mutational quantity and aneuploidy compared to other subtypes in multivariable models (p<0.001). Together with clonality patterns, this suggests that RAS mutated-only tumors exhibit a relatively younger molecular age. In a subset of patients with MAAP who underwent cytoreductive surgery, patients with RAS-only tumors demonstrate significantly lower intra-operative assessed peritoneal cancer indices (PCI) compared to patients with other molecular subtypes (p=0.049). Microscopic assessment of surgical samples reveals that RAS mutated-only tumors are significantly less likely (p<0.001) to exhibit destructive metastatic stromal invasion compared to GNAS and TP53 mutated subtypes. Molecular subtype is also a significant independent predictor of both radiographic and biochemical response to first line chemotherapy for patients with AC.

Overall, through a comprehensive profiling of the AC mutational landscape we introduce a unique disease entity of RAS-only mutated MAAP that exhibits dramatically low lethality, low peritoneal spread, and decreased tissue invasiveness despite high-risk histological characteristics. The behavior of this clinically-metastatic, but molecularly-young subtype introduces a new characterization of metastatic pathogenesis and risk that may apply to other premalignant and malignant diseases.

Citation Format: Michael B. Foote, Henry Walch, Walid Chatila, Efsevia Vakiani, Chris Chandler, Felix Steinrucke, Garrett Nash, Zsofia Stadler, Sebastian Chung, Yelena Kemel, Anna Maio, Margaret Sheehan, Nikolaus Shultz, Luis A. Diaz, Andrea Cercek. Molecular subtypes characterize appendiceal adenocarcinoma genomic evolution and disease behavior [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3474.

A Comprehensive Comparison of Early-Onset and Average-Onset Colorectal Cancers

BACKGROUND

The causative factors for the recent increase in early-onset colorectal cancer (EO-CRC) incidence are unknown. We sought to determine if early-onset disease is clinically or genomically distinct from average-onset colorectal cancer (AO-CRC).

METHODS

Clinical, histopathologic, and genomic characteristics of EO-CRC patients (2014-2019), divided into age 35 years and younger and 36-49 years at diagnosis, were compared with AO-CRC (50 years and older). Patients with mismatch repair deficient tumors, CRC-related hereditary syndromes, and inflammatory bowel disease were excluded from all but the germline analysis. All statistical tests were 2-sided.

RESULTS

In total, 759 patients with EO-CRC (35 years, n = 151; 36-49 years, n = 608) and AO-CRC (n = 687) were included. Left-sided tumors (35 years and younger = 80.8%; 36-49 years = 83.7%; AO = 63.9%; P < .001 for both comparisons), rectal bleeding (35 years and younger = 41.1%; 36-49 years = 41.0%; AO = 25.9%; P = .001 and P < .001, respectively), and abdominal pain (35 years and younger = 37.1%; 36-49 years = 34.0%; AO = 26.8%; P = .01 and P = .005, respectively) were more common in EO-CRC. Among microsatellite stable tumors, we found no differences in histopathologic tumor characteristics. Initially, differences in TP53 and Receptor Tyrosine Kinase signaling pathway (RTK-RAS)alterations were noted by age. However, on multivariate analysis including somatic gene analysis and tumor sidedness, no statistically significant differences at the gene or pathway level were demonstrated. Among advanced microsatellite stable CRCs, chemotherapy response and survival were equivalent by age cohorts. Pathogenic germline variants were identified in 23.3% of patients 35 years and younger vs 14.1% of AO-CRC (P = .01).

CONCLUSIONS

EO-CRCs are more commonly left-sided and present with rectal bleeding and abdominal pain but are otherwise clinically and genomically indistinguishable from AO-CRCs. Aggressive treatment regimens based solely on the age at CRC diagnosis are not warranted.

Abstract 1391: Self-assembling and disassembling bispecific antibody platform for pretargeted radioimmunotherapy against GPA33 in a xenograft model of colorectal peritoneal carcinomatosis

Objectives: There is increasing interest in the potential role of radioimmunotherapy in the treatment of peritoneal carcinomatosis (PC), locoregional metastasis throughout the peritoneal cavity. We recently described a SADA platform when applied to GD2-specific PRIT using beta and alpha emitting radioisotopes achieved exceptional therapeutic indices (TI) achieving tumor cures without myelo-, renal-, neuro-, or hepatic toxicities (1). We applied SADA technology to a tumor associated antigen GPA33 expressed by colorectal cancer in a PC model, and compared that to a 3 step PRIT which requires a clearing agent (CA), previously reported to produce durable responses including histologic cures of GPA33-expressing SW1222 subcutaneous (2) and intraperitoneal (ip) colorectal xenograft models (3).

Methods: SADA BsAb built from a humanized anti-GPA33 single chain Fv (scFv) and a humanized anti-DOTA scFv were expressed using the Expi293 Expression System and purified by affinity chromatography (1). Biochemical purity of &gt;90% was confirmed via size exclusion HPLC and antigen binding confirmed by surface plasmon resonance and by flow cytometry on GPA33(+) cell lines. 8 wk old female athymic nude mice were inoculated ip with 5E6 cells of stably luciferase/GFP-transfected SW1222 in 200 µL media. PC tumor progression was monitored by in vivo BLI. GPA33-SADA and control GD2-SADA were injected intravenously (iv) on day 26, followed 48 hr later with 1 mCi (37 MBq,200 pmol) [177Lu]Lu-DOTA-Bn ip. In the 3 step PRIT group, mice were treated with 250µg (1.19nmol) GPA33-BsAb (n=4) followed 24 hr later by 20 µg (2.21 nmol) of CA iv, before the injection of 1 mCi (37 MBq,200 pmol) [177Lu]Lu-DOTA-Bn ip 4 hr later. In an additional control group, no SADA was given before 1 mCi (37 MBq,200 pmol) [177Lu]Lu-DOTA-Bn ip. Biodistribution was performed 24 hr after injection of ip 177Lu radiohapten.

Results: Radioactivity absorbed in harvested ip SW1222 xenograft tumors treated with SADA-GPA33 (4.92 + 1.59 [mean + SD] percentage injected dose per gram [%ID/g]) was greater than that of harvested tumors treated with the traditional 3 step PRIT to GPA33 (2.68 + 0.179 %ID/g, p=0.043) or with negative control SADA-GD2 (0.513 + 0.293 %ID/g, p&lt;0.001). In mice treated with SADA-GPA33, the ratio of tumor-to-organ radioactivity uptake was 19.6 + 5.08 for all organs, 4.12 + 0.734 for kidneys, 30.5 + 6.14 for liver, and 122.8 + 22.6 for blood.

Conclusions: SADA-PRIT targeting GPA33 has favorable TI for colorectal PC. When compared to 3 step PRIT, SADA showed more selectivity and TI.

{{References}}: 1. Santich BH, Cheal SM, Ahmed M, et al. Clin Cancer Res. 2020; 2. Cheal SM, Xu H, Guo HF, et al. Eur J Nucl Med Mol Imaging. 2016;43(5):925-937.3. Chandler C, Cheal SM, Nash G, et al. Journal of Nuclear Medicine. 2020;61.

Citation Format: Sebastian Chung, Mao Wang, Darren Veach, Sarah Cheal, Daniela Burnes Vargas, Shin Hyuk Seo, Blesida Punzalan, Brian Santich, Hong-fen Guo, Hong Xu, Garrett Nash, Andrea Cercek, Christopher Chandler, Steven Larson, Nai-Kong Cheung. Self-assembling and disassembling bispecific antibody platform for pretargeted radioimmunotherapy against GPA33 in a xenograft model of colorectal peritoneal carcinomatosis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1391.

Clinical Calculator Based on Molecular and Clinicopathologic Characteristics Predicts Recurrence Following Resection of Stage I-III Colon Cancer

PURPOSE

Clinical calculators and nomograms have been endorsed by the American Joint Committee on Cancer (AJCC), as they provide the most individualized and accurate estimate of patient outcome. Using molecular and clinicopathologic variables, a third-generation clinical calculator was built to predict recurrence following resection of stage I-III colon cancer.

METHODS

Prospectively collected data from 1,095 patients who underwent colectomy between 2007 and 2014 at Memorial Sloan Kettering Cancer Center were used to develop a clinical calculator. Discrimination was measured with concordance index, and variability in individual predictions was assessed with calibration curves. The clinical calculator was externally validated with a patient cohort from Washington University's Siteman Cancer Center in St Louis.

RESULTS

The clinical calculator incorporated six variables: microsatellite genomic phenotype; AJCC T category; number of tumor-involved lymph nodes; presence of high-risk pathologic features such as venous, lymphatic, or perineural invasion; presence of tumor-infiltrating lymphocytes; and use of adjuvant chemotherapy. The concordance index was 0.792 (95% CI, 0.749 to 0.837) for the clinical calculator, compared with 0.708 (95% CI, 0.671 to 0.745) and 0.757 (0.715 to 0.799) for the staging schemes of the AJCC manual's 5th and 8th editions, respectively. External validation confirmed robust performance, with a concordance index of 0.738 (95% CI, 0.703 to 0.811) and calibration plots of predicted probability and observed events approaching a 45° diagonal.

CONCLUSION

This third-generation clinical calculator for predicting cancer recurrence following curative colectomy successfully incorporates microsatellite genomic phenotype and the presence of tumor-infiltrating lymphocytes, resulting in improved discrimination and predictive accuracy. This exemplifies an evolution of a clinical calculator to maintain relevance by incorporating emerging variables as they become validated and accepted in the oncologic community.

Quantitative assessment of tumor-infiltrating lymphocytes in mismatch repair proficient colon cancer

Tumor infiltrating lymphocytes (TIL), which represent host adaptive response to the tumor, were first identified at scanning magnification to select areas with the highest counts on hematoxylin and eosin slides, quantitated per high-power field (HPF), and analyzed for association with recurrence-free survival (RFS) in 848 patients. Highest TIL in a single HPF was analyzed as a continuous and categorical variable, and optimal cutoff analysis was performed to predict RFS. Highest TIL count in a single HPF ranged from 0 to 45, and the optimal cutoff for TIL high vs TIL low was determined to be ≥ 3 vs < 3 with a concordance probability estimate of 0.74. In the entire cohort, 5-year RFS was 90.2% (95% CI = 83.7–94.2) in TIL high compared to 78.9% (95% CI = 74.1–82.9) in TIL low (log rank P < .0001). TIL remained significant in the mismatch repair-proficient (pMMR) cohort where 5-year RFS was 94.6% (95% CI = 88.3–97.5) in TIL high compared to 77.9% (95% CI = 69.2–84.4) in TIL low (P = .008). On multivariable analysis, TIL and AJCC Stage were independently associated with RFS in the pMMR cohort. Qualitatively in the pMMR cohort, RFS in Stage II TIL high patients was similar to that in Stage I patients and RFS in Stage III TIL high was similar to that in Stage II TIL low patients. Assessment of TIL in a single HPF using standard H&E slides provides important prognostic information independent of MMR status and AJCC stage.

Treatment patterns and outcomes in goblet cell carcinoid tumors of the appendix

BACKGROUND

Goblet cell carcinoid (GCC) tumors of the appendix are a rare malignancy. We aim to examine the overall survival per stage and the relationship between different treatment modalities and outcomes for patients with GCC tumors of the appendix.

METHODS

We identified patients with GCC tumors of the appendix from the National Cancer Database. The main outcome was overall patient survival and cox proportional hazard models were used to ascertain predictors of survival.

RESULTS

There were 2552 patients identified. The median age of diagnosis was 57 (interquartile range: 49-65) and 52.3% of patients were female. The 5-year survival for Stage I disease was 91.1% (95% confidence interval [CI]: 82.2%-95.7%), for Stage II disease was 90.5% (95% CI: 85.8%-93.7%), for Stage III disease was 57.0% (95% CI: 45.0%-67.3%), and for Stage IV disease was 18.9% (95% CI: 9.3%-31.0%). In a Cox proportional hazard model, older age (hazard ratio [HR]: 1.1; 95% CI: 1.03-1.12; P < .001), lymph node metastasis (HR: 6.9; 95% CI: 2.76-17.01; P < .001), and positive surgical margins (HR: 2.9; 95% CI:1.13-7.26; P = .003) were associated with worse overall survival for Stages I to III disease while only older age (HR: 1.03; 95% CI: 1.002-1.06; P = .04) was associated with worse overall survival for Stage IV disease.

CONCLUSIONS

Patients with GCC tumors of the appendix who have the nonmetastatic disease have a high 5-year survival. We have identified several prognostic factors for GCC.

Induction Chemotherapy Reduces Patient-reported Toxicities During Neoadjuvant Chemoradiation with Intensity Modulated Radiotherapy for Rectal Cancer

BACKGROUND

Initial treatment with either neoadjuvant chemoradiation (CRT) or induction FOLFOX (5-Fluorouracil, leucovorin, and oxaliplatin) chemotherapy followed by CRT is considered standard treatment for locally advanced rectal cancer. We compared patient-reported outcomes (PRO) during CRT in patients who had received induction chemotherapy versus those who did not.

PATIENTS AND METHODS

We reviewed records of patients with locally advanced rectal cancer who were treated with CRT between September 2009 and October 2014, and who had completed ≥ 4 PRO assessments during treatment. Clinician- and patient-reported toxicities were collected each week during treatment. We fit binomial generalized linear models to maximum toxicity scores across all patients' visits.

RESULTS

Of 123 patients with ≥ 4 PRO assessments, 87 (71%) patients reported a clinically meaningful PRO score of 3 or higher for diarrhea, and 91 (74%) patients reported a PRO score of ≥ 3 for urgency, during 1 or more weeks of treatment, corresponding to 'very frequent' or worse. Of 116 patients who had also completed ≥ 4 clinician-reported assessments for descriptive analysis, clinically significant diarrhea (Common Terminology Criteria for Adverse Events grade ≥ 2) was reported in 9% of patients, and grade 2 proctitis and cystitis were reported in 20% and 4%, respectively. Eighty-four (68%) patients had undergone induction chemotherapy prior to CRT. Patients who received induction chemotherapy had 68% lower odds of experiencing significant urgency (odds ratio [OR], 0.32; 95% confidence interval [CI], 0.11-0.95; P = .04), 76% lower odds of bleeding (OR, 0.24; 95% CI, 0.1-0.62; P < .01), and 75% lower odds of tenesmus (OR, 0.25; 95% CI, 0.11-0.6; P < .01) versus those treated with upfront CRT.

CONCLUSION

Based on PROs, a high proportion of patients experienced clinically significant symptoms during pelvic CRT, with diarrhea and urgency being most commonly reported. This appears to be under-reported on clinician-reported assessments. Delivery of induction chemotherapy was associated with lower odds of experiencing urgency, bleeding, and tenesmus on PROs during subsequent CRT, with no significant impact on diarrhea and rectal pain.

Distance to the anal verge is associated with pathologic complete response to neoadjuvant therapy in locally advanced rectal cancer

BACKGROUND AND OBJECTIVES

Achieving a pathologic complete response (pCR) after neoadjuvant therapy has been associated with better prognosis in rectal cancer patients. The objective of this study was to investigate the relationship between distance to the anal verge (DTAV) and pCR.

METHODS

Review of a prospectively maintained database of patients with locally advanced rectal cancer who received neoadjuvant treatment was completed. Uni- and multivariate analysis assessed the association between DTAV and pCR after neoadjuvant therapy.

RESULTS

Of 827 included patients, 20% had a pCR. We found that pCR rates were 11% for tumors <4 cm, 24% for tumors 4-6 cm, 30% for tumors at 6-8 cm, 17% for tumors 8-10 cm, and 14% for tumors >10 cm from the anal verge (P = 0.002). Multivariate analysis also showed a strong association between DTAV and pCR (P = 0.008). The bimodal distribution of pCR resulted in a lower odds ratio of pCR for tumors <4 and >8 cm from the anal verge.

CONCLUSIONS

Patients with low tumors (<4 cm) and higher tumors (>8 cm), were less likely to have a pCR. Further investigation is warranted to determine if these observations are related to tumor biology or possibly differences in radiation technique. J. Surg. Oncol. 2016;114:637-641. © 2016 Wiley Periodicals, Inc.

Consensus guidelines from The American Society of Peritoneal Surface Malignancies on standardizing the delivery of hyperthermic intraperitoneal chemotherapy (HIPEC) in colorectal cancer patients in the United States

BACKGROUND

The American Society of Peritoneal Surface Malignancies (ASPSM) is a consortium of cancer centers performing cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC). This is a position paper from the ASPSM on the standardization of the delivery of HIPEC.

METHODS

A survey was conducted of all cancer centers performing HIPEC in the United States. We attempted to obtain consensus by the modified method of Delphi on seven key HIPEC parameters: (1) method, (2) inflow temperature, (3) perfusate volume, (4) drug, (5) dosage, (6) timing of drug delivery, and (7) total perfusion time. Statistical analysis was performed using nonparametric tests.

RESULTS

Response rates for ASPSM members (n = 45) and non-ASPSM members (n = 24) were 89 and 33 %, respectively. Of the responders from ASPSM members, 95 % agreed with implementing the proposal. Majority of the surgical oncologists favored the closed method of delivery with a standardized dual dose of mitomycin for a 90-min chemoperfusion for patients undergoing cytoreductive surgery for peritoneal carcinomatosis of colorectal origin.

CONCLUSIONS

This recommendation on a standardized delivery of HIPEC in patients with colorectal cancer represents an important first step in enhancing research in this field. Studies directed at maximizing the efficacy of each of the seven key elements will need to follow.

Immunoglobulin subclass determines ability of immunoglobulin (Ig)G to capture and activate neutrophils presented as normal human IgG or disease-associated anti-neutrophil cytoplasm antibody (ANCA)-IgG

Immunoglobulin G (IgG) is a potent neutrophil stimulus, particularly when presented as anti-neutrophil cytoplasm antibody (ANCA) in ANCA-associated vasculitis. We assessed whether IgG subclasses had differential effects on neutrophil activation and whether differences were dependent on specific Fc-receptor engagement. Using a physiologically relevant flow model, we compared adhesion of neutrophils to different subclasses of normal IgG coated onto solid surfaces, with adhesion of neutrophils treated with different subclasses of soluble ANCA IgG to P-selectin surfaces or endothelial cells (EC). Normal IgG captured flowing neutrophils efficiently in the order IgG3 > IgG1 > IgG2 > IgG4. Fc-receptor blockade reduced capture, IgG3 being more dependent on CD16 and IgG1/2 on CD32. Blockade of the integrin CD18 reduced neutrophil spreading, while inhibition of calcium-dependent signalling reduced both capture and spreading, suggesting that both were active processes. Neutrophils treated with ANCA IgG subclasses 1, 3 and 4 showed stabilization of adhesion to P-selectin surfaces and EC. ANCA changed neutrophil behaviour from rolling to static adhesion and the potency of the subclasses followed the same pattern as above: IgG3 > IgG1 > IgG4. Blockade of Fc receptors resulted in neutrophils continuing to roll, i.e. they were not ANCA-activated; differential utilization of Fc receptor by particular IgG subclasses was not as apparent as during neutrophil capture by normal IgG. IgG3 is the most effective subclass for inducing neutrophil adhesion and altered behaviour, irrespective of whether the IgG is surface bound or docks onto neutrophil surface antigens prior to engaging Fc receptors. Engagement of Fc receptors underpins these responses; the dominant Fc receptor depends on IgG subclass.

Re: Leucocyte depletion of perioperative blood transfusion does not affect long-term survival and recurrence in patients with gastrointestinal cancer

The Editors welcome topical correspondence from readers relating to articles published in the Journal. Responses should be sent electronically via the BJS website (www.bjs.co.uk). All letters will be reviewed and, if approved, appear on the website. A selection of these will be edited and published in the Journal. Letters must be no more than 250 words in length.

Re: Meta-analysis of defunctioning stomas in low anterior resection for rectal cancer Br J Surg (Br J Surg 2009; 96: 462-472)

The Editors welcome topical correspondence from readers relating to articles published in the Journal. Responses should be sent electronically via the BJS website (www.bjs.co.uk). All letters will be reviewed and, if approved, appear on the website. A selection of these will be edited and published in the Journal. Letters must be no more than 250 words in length.

Should indeterminate lung lesions reported on staging CT scans influence the management of patients with colorectal cancer?

OBJECTIVE

The aim of this study was to determine the significance of indeterminate lung lesions reported from staging CT scans on patients with colorectal cancer.

METHOD

CT-scan reports of 439 patients were reviewed to identify patients in which indeterminate lung lesion had been reported. The tumour, node, metastasis (TNM) stage of these patients was recorded together with any follow-up scan reports or multidisciplinary team (MDT) discussions regarding these lesions.

RESULTS

Twenty-three patients had definite lung metastases. Forty-five patients had indeterminate lung lesions. Of these, 22 patients had N1 or N2 disease, 20 had N0 disease and three patients were not operated on due to comorbidity. Of these 45 patients, 30 had further follow-up scans. In 19, the indeterminate lesions were unchanged and were therefore downgraded to benign lesions. The lesions had progressed or new lesions had developed in five. These patients were therefore shown to have metastatic lung disease. All five of these patients had N1 or N2 disease. One patient had a primary rather than metastatic lung lesion. Follow-up scans showed the lesion to be no longer present in five. Of the remainder, One patient declined further follow up. Three patients did not have a follow up scan for reasons not mentioned in their records. Two patients were not scanned because further MDT review of the original scans showed that the lesions were not metastases. Four patients died before follow up scans were done. (one postoperative myocardial infarction (MI), one postoperative sepsis, one postoperative cerebrovascular accident (CVA) and one inferior vena cava (IVC) obstruction). Five patients have not yet had follow-up scan at the time of writing.

CONCLUSION

Since the introduction of spiral CT scanners, smaller lesions are being seen at the time of preoperative staging. Our study concludes that only a small proportion of indeterminate lung lesions did develop into definite metastases and those that did had node positive disease. Indeterminate lung lesions are not a reason to delay surgery for colorectal cancer.

Lymph node metastasis in T1 adenocarcinoma of the colon and rectum

The biology of colorectal cancer differs according to location within the large intestine. To evaluate the clinical significance of tumor location as a risk factor for lymph node metastasis (LNM), we performed a detailed pathological review of T1 adenocarcinomas of the colon and rectum. T1 adenocarcinomas of the colon and rectum treated by radical resection (n=428) were identified from prospective clinical databases at two institutions. Tumor location was assigned as right colon (cecum to transverse), left colon (splenic flexure to sigmoid), or rectum (0-18 cm from AV). Pathology slides were reviewed, extent of submucosal invasion (sm width, sm depth) was quantified using an optical micrometer, and morphologic features of the cancer and its infiltrating margin were recorded. The overall rate of LNM was 10%. On univariate analysis, LNM was significantly more common in the rectum (27/176, 15%) compared to the left colon (13/160, 8%, p=.04) or right colon (3/92, 3%, p=.003). However, on multivariate analysis, deep submucosal invasion and lymphovascular invasion were independent and significant risk factors, whereas tumor location was not. T1 colorectal cancers have a progressively higher risk of LNM as their location becomes more distal. However, the increasing rate of LNM observed in cancers of the left colon and rectum is explained by a higher prevalence of high-risk pathologic features. In early colorectal cancers, tumor morphology is the strongest clinical predictor of metastatic behavior.

Comparison of the effects of radiographic contrast media on dehydration and filterability of red blood cells from donors homozygous for hemoglobin A or hemoglobin S

Iodinated radiographic contrast media have traditionally been contraindicated in patients with sickle cell disease because their high osmolality may induce osmotic shrinkage of red blood cells, impair blood flow through the microcirculation, and precipitate or exacerbate a sickle cell crisis. This study investigated that concept by comparing the hematological and rheological effects in vitro of four X-ray contrast media of differing osmolalities: Visipaque (290 mOsm/kg), Hexabrix (600 mOsm/kg), Omnipaque (844 mOsm/kg), and RenoCal-76 (1940 mOsm/kg). Blood was tested from 10 normal and 10 sickle cell donors at drug concentrations of 0, 1, 10, and 30% w/v in an attempt to approximate the relative concentrations of contrast medium to blood that might occur during the bolus-injection and circulation-diluted phases of drug administration. Parameters evaluated included hematology, red cell morphology, and red cell flow resistance through a micropore filter to approximate the microcirculatory effects. Significant hematological effects for both normal and sickle cell donors included a concentration dependent decrease in hematocrit and MCV, and increase in MCHC, all of which varied directly with the osmolality of the contrast media in the order of RenoCal-76 > Omnipaque > Hexabrix > Visipaque. The contrast media had minor effects on red blood cell morphology except for RenoCal-76, 10-30% in which marked echinocytosis was observed. There was no significant increase in the number of irreversibly sickled cells in donors with hemoglobin S. Filterability of red cell suspensions through capillary size pores was impaired in both normal and sickle cell samples in direct proportion to the osmolality of the contrast media, as listed above. Filterability effects were greater for sickle cells than for normal red cells. Visipaque, which was closest to isotonicity, had little effect on red cell volume and had no significant effect on filterability of normal or sickle cells. These results suggest that microcirculatory impairment following infusion of contrast media may occur in sickle patients because of the unusual rheological sensitivity of HbSS red cells, and may be avoided by choice of an isotonic medium.