Single-center prospective study on the efficacy of nivolumab against platinum-sensitive recurrent or metastatic head and neck squamous cell carcinoma

Nivolumab, an immune checkpoint inhibitor, is beneficial to patients with platinum-refractory recurrent or metastatic head and neck squamous cell carcinoma (R/M-HNSCC). However, platinum-sensitive R/M-HNSCC has not yet been studied. Hence, in this prospective study, we evaluated the efficacy and safety of nivolumab in patients with platinum-sensitive R/M-HNSCC. This prospective single-arm study was conducted in a single institution in Japan. Patients with platinum-sensitive R/M-HNSCC (defined as head and neck cancer that recurred or metastasized at least 6 months after platinum-based chemotherapy or chemoradiotherapy) were enrolled. The primary endpoint was overall survival (OS). The secondary endpoints were progression-free survival (PFS), overall response rate (ORR), immune-related adverse events (irAEs), and quality of life (QOL). This study was registered at the University Hospital Medical Information Network Clinical Trials Registry (UMIN000031324). Twenty-two patients with platinum-sensitive R/M-HNSCC were enrolled. The median OS was 17.4 months, and the 1-year OS rate was 73%. The median PFS was 9.6 months, 1-year PFS rate was 48%, and ORR was 36%. Sixteen irAEs were recorded in 12 patients; however, no grade 4 or 5 irAEs were observed. The QOL assessments revealed that nivolumab did not decrease the QOL of patients. Nivolumab is effective against platinum-sensitive R/M-HNSCC with acceptable safety.

The Role of the EZH2 and H3K27me3 Expression as a Predictor of Clinical Outcomes in Salivary Duct Carcinoma Patients: A Large-Series Study With Emphasis on the Relevance to the Combined Androgen Blockade and HER2-Targeted Therapy

Objective

Salivary duct carcinoma (SDC) is a highly aggressive and uncommon tumor arising not only de novo but also in pleomorphic adenoma. Androgen receptor (AR)- and HER2-targeted therapy have recently been introduced for SDC as promising treatment options; however, no predictive biomarkers have yet been established. EZH2 and H3K27me3 are closely linked to the development and progression of various cancers, and EZH2 is also expected to be a desirable therapeutic target. We therefore explored the clinicopathological and prognostic implications of EZH2 and H3K27me3 in a large cohort of SDC patients, focusing on their impact on the therapeutic efficacy of AR- or HER2-targeted therapy.

Materials and Methods

The EZH2 and H3K27me3 immunohistochemical expression and EZH2 Y646 gain-of-function mutation status were examined in 226 SDCs, and the relationship with the clinicopathological factors as well as clinical outcomes were evaluated within the three groups depending on the treatment: AR-targeted (combined androgen blockade with leuprorelin acetate and bicalutamide; 89 cases), HER2-targeted (trastuzumab and docetaxel; 42 cases), and conventional therapy (112 cases).

Results

EZH2 and H3K27me3 were variably immunoreactive in most SDCs. A positive correlation was found between the expression of EZH2 and H3K27me3. The EZH2 expression in the SDC component was significantly higher than that in the pre-existing pleomorphic adenoma component. EZH2 Y646 was not identified in any cases. EZH2-high cases more frequently had an advanced clinical stage and aggressive histological features than EZH2-low cases. An EZH2-high status in patients treated with AR-targeted therapy was associated with a significantly shorter progression-free and overall survival as well as a lower objective response rate and clinical benefit rate. In addition, a H3K27me3-high status in patients treated with AR-targeted therapy was related to a shorter overall survival. Conversely, there was no association between the EZH2 and H3K27me3 expression and the clinical outcomes in the conventional or HER2-targeted therapy groups.

Conclusions

A high expression of EZH2 and H3K27me3 in SDC might be a predictor of a poor efficacy of AR-targeted therapy. Our data provide new insights into the role of EZH2 and H3K27me3 in therapeutic strategies for SDC.

Photoimmunotherapy for Managing Recurrent Laryngeal Cancer Cervical Lesions: A Case Report

Photoimmunotherapy (PIT) targets and destroys tumor cells through irradiation with 690-nm red light after the administration of cetuximab sarotalocan sodium, which contains IRDye700DX bound to cetuximab. In Japan, PIT is a new treatment that is covered by insurance only for unresectable head and neck cancers. However, this treatment has conditional early approval. There have been no case reports describing the efficacy of this treatment in a real-world setting thus far. We report our experience with PIT for head and neck cancer. A 76-year-old man with laryngeal cancer underwent radiation therapy and surgery. Skin involvement in the right submandibular region was subsequently noted. We diagnosed local recurrence and performed PIT for this lesion. Partial response was achieved after the first PIT session, and progressive disease was diagnosed after the second session. Many aspects of PIT remain unclear and should, therefore, be clarified in further research. Despite this uncertainty, PIT may become an effective treatment strategy for head and neck cancer if the patient selection criteria are delineated.

Assessment of the albumin-bilirubin grade as a prognostic factor in patients with non-small-cell lung cancer receiving anti-PD-1-based therapy

Introduction

The albumin-bilirubin (ALBI) grade is a novel indicator of the liver function. Some studies showed that the ALBI grade was a prognostic and predictive biomarker for the efficacy of chemotherapy in cancer patients. The association between the ALBI grade and outcomes in patients with non-small-cell lung cancer (NSCLC) treated with cancer immunotherapy, however, is poorly understood.

Methods

We retrospectively enrolled 452 patients with advanced or recurrent NSCLC who received anti-programmed cell death protein 1 (PD-1)-based therapy between 2016 and 2019 at three medical centers in Japan. The ALBI score was calculated from albumin and bilirubin measured at the time of treatment initiation and was stratified into three categories, ALBI grade 1-3, with reference to previous reports. We examined the clinical impact of the ALBI grade on the outcomes of NSCLC patients receiving anti-PD-1-based therapy using Kaplan–Meier survival curve analysis with log-rank test and Cox proportional hazards regression analysis.

Results

The classifications of the 452 patients were as follows: grade 1, n = 158 (35.0%); grade 2, n = 271 (60.0%); and grade 3, n = 23 (5.0%). Kaplan–Meier survival curve analysis showed that the ALBI grade was significantly associated with progression-free survival and overall survival. Moreover, Cox regression analysis revealed that the ALBI grade was an independent prognostic factor for progression-free survival and overall survival.

Conclusion

The ALBI grade was an independent prognostic factor for survival in patients with advanced or recurrent NSCLC who receive anti-PD-1-based therapy. These findings should be validated in a prospective study with a larger sample size.

•

ALBI grade is calculated from albumin and bilirubin.

•

We evaluated the impact of ALBI grade on survival in NSCLC patients receiving immune checkpoint inhibitors.

•

ALBI grade was an independent prognostic factor for progression-free survival (PFS) and overall survival (OS).

•

ALBI grade effectively stratified PFS and OS in patients with performance status 1-3.

•

ALBI grade was significantly associated with PFS and OS, regardless of programmed death ligand-1.

Effect of Concomitant Lafutidine on Adjuvant S-1 for Head and Neck Cancer: A Comparative Study

BACKGROUND/AIM

This study evaluated the utility of the histamine H2-receptor antagonist lafutidine in patients taking oral fluorouracil (S-1) for head and neck squamous cell carcinoma (HNSCC), by comparing patients with and without concomitant lafutidine.

PATIENTS AND METHODS

Study subjects comprised 63 patients who received adjuvant S-1 following curative resection of HNSCC at our institutions between August 1, 2013 and December 31, 2019. The primary endpoint was the completion rate of S-1 therapy.

RESULTS

For the lafutidine-treated group, the median completion rate was significantly greater (94.4% vs. 24.6%, p=0.01), and progression-free and overall survival were both significantly prolonged compared to the non-lafutidine group. In terms of adverse events, the incidence of diarrhoea was significantly reduced (p<0.00189) in the lafutidine-treated group.

CONCLUSION

Taking lafutidine during S-1 treatment appeared to reduce gastrointestinal disturbance and increased the S-1 completion rate, improving both progression-free and overall survival as a result.

Transoral Endoscopic Examination of the Oropharynx With Tongue Protrusion, Phonation, and Open Mouth

BACKGROUND/AIM

We examined the diagnostic performance of the tongue protrusion with phonation and open mouth (TOPPOM) method for visualizing structures of the oropharynx.

PATIENTS AND METHODS

Transoral endoscopy was performed on 20 healthy participants to evaluate 12 oropharynx subsites under three conditions: open mouth (OM), phonation with open mouth (POM), and TOPPOM. Each subsite was scored from 0 to 2 depending on subsite visualization, and the scores were summed. Images of subsite-adjacent mucosa were similarly scored.

RESULTS

The total scores were significantly higher for TOPPOM than for POM and for POM than for OM. Such scores were observed for both the palatine arches, both palatine tonsils, the left lingual tonsillar sulcus, and the vallecula.

CONCLUSION

TOPPOM enables visualization of the oropharynx through transoral endoscopic examination, and TOPPOM with conventional transnasal endoscopy may enable early detection of oropharyngeal carcinomas and lesions and improve the performance of pre- and post-treatment evaluations.

Postoperative Complications of Jejunal and Skin Valve Reconstruction in Free Reconstructive Surgery for Hypopharyngeal Carcinoma

BACKGROUND/AIM

This study evaluated the incidence of perioperative complications in jejunal flap compared with the free tissue flap approach.

PATIENTS AND METHODS

This study included 75 patients who underwent free flap reconstruction for hypopharyngeal carcinoma. The primary outcome was the incidence of pharyngocutaneous fistula, and the secondary outcomes were perioperative complications.

RESULTS

Pharyngocutaneous fistula developed in 7% of patients who underwent jejunal flap procedures and 6% of patients who underwent free tissue flap procedure. Flap sampling site complications occurred in 23% of patients who underwent jejunal flap procedures and in none of the patients who underwent free tissue flap procedure.

CONCLUSION

No significant difference was observed in the incidence of pharyngocutaneous fistula between the two groups (p=0.99), but complications at the flap sampling site were significantly more common in jejunal flap procedures than in free tissue flap procedures (p=0.03). Free tissue flap procedures are potential reconstruction methods superior to jejunal flap methods.

Changes in carnitine levels through induction chemotherapy in head and neck cancer patients as a potential cause of therapy-related malaise

Background

Carnitine is related to malaise, and cisplatin is associated with decreased carnitine. The purpose of this study was to elucidate the effects of one course of induction chemotherapy (IC) for head and neck cancer on blood carnitine levels, focusing on free carnitine (FC).

Methods

This single-center prospective study investigated 20 patients diagnosed with primary head and neck cancer who underwent IC with cisplatin, docetaxel, and 5-fluorouracil. FC, acylcarnitine (AC), and total carnitine (TC) levels were measured before starting therapy and on Days 7 and 21 after starting IC. In addition, malaise was evaluated before and after therapy using a visual analog scale (VAS).

Results

All subjects were men and the most common primary cancer site was the hypopharynx (9 patients). FC levels before starting therapy and on Days 7 and 21 were 47.7 ± 2.2 μM/mL, 56.7 ± 2.2 μM/mL, and 41.1 ± 1.9 μM/mL, respectively. Compared with the baseline before starting therapy, FC had significantly decreased on Day 21 (p = 0.007). AC levels before starting therapy and on Days 7 and 21 were 12.5 ± 1.2 μM/mL, 13.6 ± 1.4 μM/mL, and 10.7 ± 0.7 μM/mL, respectively. TC levels before starting therapy and on Days 7 and 21 were 60.2 ± 2.5 μM/mL, 70.2 ± 3.3 μM/mL, and 51.7 ± 2.3 μM/mL, respectively. No significant differences in AC, TC or VAS were seen before the start of therapy and on Day 21.

Conclusions

After IC, a latent decrease in FC occurred without any absolute deficiency or subjective malaise.

Investigation of the Efficacy and Safety of Nivolumab in Recurrent and Metastatic Nasopharyngeal Carcinoma

BACKGROUND/AIM

Nivolumab, an anti-PD-1 inhibitor, has demonstrated efficacy in patients with several types of recurrent and metastatic (R/M) squamous cell carcinoma of the head and neck. We evaluated patients with R/M-NPC receiving nivolumab.

PATIENTS AND METHODS

Twelve patients with R/M-NPC were enrolled at 4 institutions. The primary endpoint was overall survival, and secondary endpoints were i) progression-free survival (PFS), ii) overall response rate (ORR), iii) disease control rate (DCR), and iv) treatment-related toxicity.

RESULTS

The 1-year survival rate was 75.8%, the median PFS was 2.8 months, and the 1-year PFS rate was 33.3%. The best therapeutic response was complete response in 2, stable disease in 3 and progressive disease in 7 patients. The ORR of all patients was 16.7% and the DCR was 41.7%.

CONCLUSION

Nivolumab is a useful and relatively safe second-line systemic therapy in patients with R/M-NPC, and even patients who do not respond to nivolumab may survive for a long time.

Efficacy and Safety of Paclitaxel Combined With Cetuximab for Head and Neck Squamous Cell Carcinoma

BACKGROUND/AIM

For recurrent/metastatic squamous cell carcinoma of the head and neck (R/M SCCHN), popular regimens containing platinum-based anticancer agents and immune checkpoint inhibitors are impractical for platinum-intolerant patients. Herein, the efficacy and safety of paclitaxel and cetuximab combination therapy in R/M SCCHN were evaluated.

PATIENTS AND METHODS

In this retrospective study, paclitaxel (80 mg/m2) and cetuximab (400 mg/m2 loading dose followed by 250 mg/m2 weekly) were administered in 28-day cycles on days 1, 8, and 15.

RESULTS

Thirty-eight patients were treated. The overall response and disease control rates of first-line therapy were 43% and 79%, respectively, while those of second-line and later therapies were 20% and 90%, respectively. The median progression-free and overall survival were 5.3 and 12.5 months, respectively. All adverse events were manageable, including grade 3/4 neutropenia and anaemia affecting 8-13% of patients.

CONCLUSION

Paclitaxel and cetuximab combination therapy may be suitable for treating R/M SCCHN.

Predicting the efficacy of chemoradiotherapy for locally advanced human papilloma virus-related oropharyngeal squamous cell carcinoma using one course of TPF chemotherapy

PURPOSE

The standard induction chemotherapy for head and neck cancer is TPF [cisplatin (CDDP), docetaxel (DOC), and 5-fluorouracil (5-FU)]. We assessed whether one course of TPF could predict the efficacy of chemoradiotherapy for human papilloma virus (HPV)-related oropharyngeal squamous cell carcinoma.

METHODS

We retrospectively reviewed 51 patients with stage III-IV HPV-related oropharyngeal squamous cell carcinoma who received one course of TPF with CDDP 60 mg/m², DOC 60 mg/m², and 5-FU 600 mg/m². We recommended chemoradiotherapy for patients with complete or partial response (CR/PR), and surgery for those with stable or progressive disease (SD/PD). The endpoints were TPF-related adverse events and efficacy, chemoradiotherapy efficacy, and 2-year survival.

RESULTS

Neutropenia was the most common grade ≥ 3 adverse event (88%). No grade 5 adverse events occurred. TPF achieved CR in 4% of patients (2/51), PR in 73% (37/51), SD in 20% (10/51), and PD in 4% (2/51). Concurrent cetuximab and radiotherapy (bio-radiotherapy, BRT) were administered to 61% of patients (31/51), concurrent CDDP and radiotherapy (CDDP-RT) to 16% (8/51), RT alone to 2% (1/51), and surgery was performed for 22% (11/51). CR was achieved in 85% of the chemoradiotherapy group, and the rate tended to increase with TPF efficacy. CR was achieved in 84% (26/31) of patients receiving BRT, 88% (7/8) receiving CDDP-RT, and 100% (1/1) receiving RT. The 2-year survival rates were 92% overall, and 97% and 79% in the chemoradiotherapy and surgery groups, respectively.

CONCLUSIONS

When facing difficulty in deciding between chemoradiotherapy and surgery, one course of TPF may be an effective option.

Erlotinib plus bevacizumab vs erlotinib monotherapy as first-line treatment for advanced EGFR mutation-positive non-squamous non-small-cell lung cancer: Survival follow-up results of the randomized JO25567 study

OBJECTIVES

The JO25567 randomized Phase II study demonstrated a statistically significant progression-free survival (PFS) benefit with erlotinib plus bevacizumab compared with erlotinib monotherapy in chemotherapy-naïve Japanese patients with epidermal growth factor receptor mutation-positive (EGFR+) non-small-cell lung cancer (NSCLC). Here we present updated PFS and final overall survival (OS) data after a median follow-up of 34.7 months.

MATERIALS AND METHODS

Patients with stage IIIB/IV or postoperative recurrent NSCLC were randomized to receive oral erlotinib 150 mg once daily (n = 77) or erlotinib in combination with intravenous bevacizumab 15 mg/kg every 21 days (n = 75) until disease progression or unacceptable toxicity. OS was analyzed using an unstratified Cox proportional hazards model.

RESULTS

Consistent with the primary analysis, addition of bevacizumab to erlotinib was associated with a significant improvement in PFS (hazard ratio [HR] 0.52; 95 % confidence interval [CI]: 0.35-0.76; log-rank two-sided P = 0.0005; median 16.4 months vs 9.8 months, respectively). In contrast, a significant improvement in OS was not seen (HR 0.81; 95 % CI, 0.53-1.23; P =  0.3267; median 47.0 months vs 47.4 months, respectively). Post-study therapy was similar between the treatment arms and EGFR mutation type did not affect OS outcomes. The 5-year OS rate was numerically higher with erlotinib plus bevacizumab vs erlotinib monotherapy (41 % vs 35 %). Updated safety analyses confirmed the previously reported manageable tolerability profile, with no new safety issues.

CONCLUSION

Addition of bevacizumab to first-line erlotinib did not show significant improvement in OS in Japanese patients with stage IIIB/IV or postoperative recurrent EGFR+ NSCLC. Both treatment arms showed a similar median OS benefit (as long as 4 years), irrespective of individual patient characteristics. Results from ongoing studies evaluating the combination of EGFR and VEGF signaling inhibitors are eagerly awaited.

TRIAL REGISTRATION

JapicCTI-111390 and JapicCTI-142569.

Resection of Parapharyngeal Space Tumors Located in the Prestyloid Compartment: Efficacy of the Cervical Approach

BACKGROUND

Parapharyngeal space tumors are rare. Among them, tumors in the prestyloid compartment are particularly suitable for surgery; however, there are no detailed reports of such surgery and their features remain unknown.

METHODS

We conducted a retrospective cohort study. For 67 surgical cases of benign tumors in this compartment, we examined the patient and tumor characteristics, fine-needle aspiration cytology (FNAC), and intraoperative details such as surgical approach, use of complete excision, and postoperative complications.

RESULTS

Pleomorphic adenomas (PAs) comprised 73.1% of the lesions. The diagnostic accuracy of FNAC to differentiate benign and malignant tumors was 97.7%. Of the treated lesions, 94.0% were removed via the cervical approach alone, including all PAs. The remaining 6.0% were resected via the cervical-parotid approach. The median operative time and bleeding volume were 89 min and 50 mL, respectively. Operative time using the cervical approach was significantly shorter (p = 0.021). All cases could be treated via complete surgical excision. Postoperative complications occurred in 32.8% of patients, with transient slight facial palsy being the most common. No fatal complications occurred and 92.5% of patients had no sequelae. There was no significant association between complications and surgical approach.

CONCLUSION

Based on diagnosis by FNAC, with a high accuracy rate, most benign prestyloid tumors, especially PAs, were resected using the cervical approach alone, with a shorter operative time and without severe complications.

Co-treatment with endoscopic laryngopharyngeal surgery and endoscopic submucosal dissection

OBJECTIVE

Endoscopic laryngopharyngeal surgery (ELPS) is an effective and minimally invasive treatment for pharyngeal cancers. However, the disadvantages of ELPS are the interference of instruments in the operative field and the difficulty in approaching certain areas. To overcome these drawbacks, we began to perform combination treatment of ELPS and endoscopic submucosal dissection (ESD). The aim of the present study was to compare the efficacies of treatment with ELPS alone and ELPS combined with ESD.

METHODS

A total of 103 lesions in 73 patients who underwent pharyngeal ELPS for superficial pharyngeal cancer between August 2014 and January 2020 at our hospital were analyzed. Lesions were divided into the ELPS alone group and ELPS combined with ESD group. Lesion characteristics, technical results, adverse events, and long-term outcomes were analyzed.

RESULTS

In the ELPS combined with ESD group, procedure speed was shorter than the ELPS alone group (20.2 ± 10.0 mm²/min vs 13.0 ± 6.6 mm²/min, p < 0.001), and R0 resection rate was higher (67.4% vs 45.6%, p = 0.027). There were no significant differences in tumor size, depth of tumor invasion, and adverse events among the 2 groups. These results remained unchanged after propensity score matching. The overall and cause-specific survival rates at 3 years were 96.7% and 100% for the ELPS combined with ESD group and ELPS alone group, respectively.

CONCLUSIONS

Combination treatment of ESD and ELPS enabled more efficient resection than ELPS alone. Cooperative treatment of pharyngeal cancer patients involving gastroenterologists and head and neck surgeons is effective and beneficial, and results in favorable long-term outcomes.

Multicentre, retrospective study of the efficacy and safety of nivolumab for recurrent and metastatic salivary gland carcinoma

Although immune-checkpoint inhibitors (ICIs) are effective against various cancers, little is known regarding their role in salivary gland carcinoma (SGC) treatment. Therefore, we evaluated the efficacy and safety of nivolumab monotherapy in patients with recurrent and/or metastatic SGC. In this multicentre retrospective study, nivolumab (240 mg) was administered every 2 weeks. The overall response rate (ORR), progression-free survival (PFS), overall survival (OS), and safety were examined; the correlation between treatment outcomes and clinicopathological factors was analysed. Twenty-four patients were enrolled; the most common histopathology was salivary duct carcinoma. Eleven tumours were PD-L1-positive; no tumour was microsatellite instability-high. The ORR was 4.2%, and the median PFS and OS were 1.6 and 10.7 months, respectively. One patient continued nivolumab for 28 months without disease progression. One patient showed grade 4 increase in creatine phosphokinase levels and grade 3 myositis. Biomarker analysis revealed significantly increased OS in patients with performance status of 0; modified Glasgow prognostic score of 0; low neutrophil-to-lymphocyte ratio, lactate dehydrogenase, and C-reactive protein; and high lymphocyte-to-monocyte ratio and in patients who received systemic therapy following nivolumab. Although nivolumab's efficacy against SGC was limited, some patients achieved long-term disease control. Further studies are warranted on ICI use for SGC.

Second postoperative hemorrhage five weeks after transoral robotic surgery

Transoral robotic surgery (TORS) is becoming widely used in Japan, and information on postoperative hemorrhage is needed. We treated a patient who developed a second massive postoperative hemorrhage on Day 35 post-TORS. The 69-year-old man was diagnosed with p16-positive, T1N1M0 stage I cancer of the anterior wall of the oropharynx. Curative treatment began with right neck dissection. The external carotid artery and its branches were not ligated. One month after right neck dissection, TORS was conducted. On Day 23 post-TORS, the patient was brought to the emergency room due to pharyngeal bleeding. Hemorrhage was stopped by reclosing the site with Z-shaped silk sutures. Severe hemorrhage recurred on Day 35 post-TORS. The patient went into hemorrhagic shock. Tracheostomy was immediately performed. The neck dissection wound was then opened and the external carotid artery clamped. Hemostasis was confirmed transorally, but the hemorrhage site was again sutured with Z-shaped silk sutures to stop the bleeding. The patient was discharged on Day 58 post-TORS. Even in hindsight, this hemorrhage would have been difficult to prevent with better local treatment. This means that using transcervical arterial ligation together with TORS is appropriate from the perspective of making every effort to prevent potentially fatal postoperative hemorrhage.

Prediction of Therapeutic Effects from One Course of TPF Chemotherapy for Advanced Hypopharyngeal Laryngeal Cancer

BACKGROUND

In head and neck cancer, docetaxel, cisplatin and 5-fluorouracil (TPF) is often given in two or three cycles. The purpose of this study was to perform single-cycle TPF for chemoselection in patients with advanced hypopharyngeal laryngeal cancer.

PATIENTS AND METHODS

The study included 56 patients with stage III/IV advanced hypopharyngeal/laryngeal squamous cell carcinoma. The primary endpoint was progression-free survival (PFS), and secondary endpoints were overall survival (OS), TPF response rate, laryngeal sparing, and grade 3 or more adverse events.

RESULTS

The median PFS was 34.8 months. The median OS was not evaluable. The response rate was 71%. The median laryngeal preservation period was not estimable. Grade 3 or 4 adverse events were reported in 46 patients.

CONCLUSION

PFS rate in this study may have been improved by selecting surgical treatment for patients for whom chemoradiotherapy seemed less effective. One cycle of TPF in induction chemotherapy appeared effective for chemoselection.